+Single directory performance is a critical for HPC workloads. In a
+typical use case an application creates a separate output file for
+each node and task in a job. As nodes and tasks increase, hundreds
+of thousands of files may be created in a single directory within
+a short window of time.
+Today, both filename lookup and file system modifying operations
+(such as create and unlink) are protected with a single lock for
+an entire ldiskfs directory. PDO project will remove this
+bottleneck by introducing a parallel locking mechanism for entire
+ldiskfs directories. This work will enable multiple application
+threads to simultaneously lookup, create and unlink in parallel.
+
+This patch contains:
+ - pdirops support for ldiskfs
+ - integrate with osd-ldiskfs
+
+Index: linux-4.18.0-80.1.2.el8_0/fs/ext4/Makefile
+===================================================================
+--- linux-4.18.0-80.1.2.el8_0.orig/fs/ext4/Makefile
++++ linux-4.18.0-80.1.2.el8_0/fs/ext4/Makefile
+@@ -7,6 +7,7 @@ obj-$(CONFIG_EXT4_FS) += ext4.o
+
+ ext4-y := balloc.o bitmap.o block_validity.o dir.o ext4_jbd2.o extents.o \
+ extents_status.o file.o fsmap.o fsync.o hash.o ialloc.o \
++ htree_lock.o \
+ indirect.o inline.o inode.o ioctl.o mballoc.o migrate.o \
+ mmp.o move_extent.o namei.o page-io.o readpage.o resize.o \
+ super.o symlink.o sysfs.o xattr.o xattr_trusted.o xattr_user.o
+Index: linux-4.18.0-80.1.2.el8_0/fs/ext4/ext4.h
+===================================================================
+--- linux-4.18.0-80.1.2.el8_0.orig/fs/ext4/ext4.h
++++ linux-4.18.0-80.1.2.el8_0/fs/ext4/ext4.h
+@@ -29,6 +29,7 @@
+ #include <linux/timer.h>
+ #include <linux/version.h>
+ #include <linux/wait.h>
++#include <linux/htree_lock.h>
+ #include <linux/sched/signal.h>
+ #include <linux/blockgroup_lock.h>
+ #include <linux/percpu_counter.h>
+@@ -934,6 +935,9 @@ struct ext4_inode_info {
+ __u32 i_dtime;
+ ext4_fsblk_t i_file_acl;
+
++ /* following fields for parallel directory operations -bzzz */
++ struct semaphore i_append_sem;
++
+ /*
+ * i_block_group is the number of the block group which contains
+ * this file's inode. Constant across the lifetime of the inode,
+@@ -2109,6 +2113,72 @@ struct dx_hash_info
+ */
+ #define HASH_NB_ALWAYS 1
+
++/* assume name-hash is protected by upper layer */
++#define EXT4_HTREE_LOCK_HASH 0
++
++enum ext4_pdo_lk_types {
++#if EXT4_HTREE_LOCK_HASH
++ EXT4_LK_HASH,
++#endif
++ EXT4_LK_DX, /* index block */
++ EXT4_LK_DE, /* directory entry block */
++ EXT4_LK_SPIN, /* spinlock */
++ EXT4_LK_MAX,
++};
++
++/* read-only bit */
++#define EXT4_LB_RO(b) (1 << (b))
++/* read + write, high bits for writer */
++#define EXT4_LB_RW(b) ((1 << (b)) | (1 << (EXT4_LK_MAX + (b))))
++
++enum ext4_pdo_lock_bits {
++ /* DX lock bits */
++ EXT4_LB_DX_RO = EXT4_LB_RO(EXT4_LK_DX),
++ EXT4_LB_DX = EXT4_LB_RW(EXT4_LK_DX),
++ /* DE lock bits */
++ EXT4_LB_DE_RO = EXT4_LB_RO(EXT4_LK_DE),
++ EXT4_LB_DE = EXT4_LB_RW(EXT4_LK_DE),
++ /* DX spinlock bits */
++ EXT4_LB_SPIN_RO = EXT4_LB_RO(EXT4_LK_SPIN),
++ EXT4_LB_SPIN = EXT4_LB_RW(EXT4_LK_SPIN),
++ /* accurate searching */
++ EXT4_LB_EXACT = EXT4_LB_RO(EXT4_LK_MAX << 1),
++};
++
++enum ext4_pdo_lock_opc {
++ /* external */
++ EXT4_HLOCK_READDIR = (EXT4_LB_DE_RO | EXT4_LB_DX_RO),
++ EXT4_HLOCK_LOOKUP = (EXT4_LB_DE_RO | EXT4_LB_SPIN_RO |
++ EXT4_LB_EXACT),
++ EXT4_HLOCK_DEL = (EXT4_LB_DE | EXT4_LB_SPIN_RO |
++ EXT4_LB_EXACT),
++ EXT4_HLOCK_ADD = (EXT4_LB_DE | EXT4_LB_SPIN_RO),
++
++ /* internal */
++ EXT4_HLOCK_LOOKUP_SAFE = (EXT4_LB_DE_RO | EXT4_LB_DX_RO |
++ EXT4_LB_EXACT),
++ EXT4_HLOCK_DEL_SAFE = (EXT4_LB_DE | EXT4_LB_DX_RO | EXT4_LB_EXACT),
++ EXT4_HLOCK_SPLIT = (EXT4_LB_DE | EXT4_LB_DX | EXT4_LB_SPIN),
++};
++
++extern struct htree_lock_head *ext4_htree_lock_head_alloc(unsigned hbits);
++#define ext4_htree_lock_head_free(lhead) htree_lock_head_free(lhead)
++
++extern struct htree_lock *ext4_htree_lock_alloc(void);
++#define ext4_htree_lock_free(lck) htree_lock_free(lck)
++
++extern void ext4_htree_lock(struct htree_lock *lck,
++ struct htree_lock_head *lhead,
++ struct inode *dir, unsigned flags);
++#define ext4_htree_unlock(lck) htree_unlock(lck)
++
++extern struct buffer_head *__ext4_find_entry(struct inode *dir,
++ const struct qstr *d_name,
++ struct ext4_dir_entry_2 **res_dir,
++ int *inlined, struct htree_lock *lck);
++extern int __ext4_add_entry(handle_t *handle, struct dentry *dentry,
++ struct inode *inode, struct htree_lock *lck);
++
+ struct ext4_filename {
+ const struct qstr *usr_fname;
+ struct fscrypt_str disk_name;
+@@ -2416,8 +2486,16 @@ void ext4_insert_dentry(struct inode *in
+ struct ext4_filename *fname, void *data);
+ static inline void ext4_update_dx_flag(struct inode *inode)
+ {
++ /* Disable it for ldiskfs, because going from a DX directory to
++ * a non-DX directory while it is in use will completely break
++ * the htree-locking.
++ * If we really want to support this operation in the future,
++ * we need to exclusively lock the directory at here which will
++ * increase complexity of code */
++#if 0
+ if (!ext4_has_feature_dir_index(inode->i_sb))
+ ext4_clear_inode_flag(inode, EXT4_INODE_INDEX);
++#endif
+ }
+ static const unsigned char ext4_filetype_table[] = {
+ DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
+Index: linux-4.18.0-80.1.2.el8_0/fs/ext4/htree_lock.c
+===================================================================
+--- /dev/null
++++ linux-4.18.0-80.1.2.el8_0/fs/ext4/htree_lock.c
+@@ -0,0 +1,891 @@
++/*
++ * fs/ext4/htree_lock.c
++ *
++ * Copyright (c) 2011, 2012, Intel Corporation.
++ *
++ * Author: Liang Zhen <liang@whamcloud.com>
++ */
++#include <linux/jbd2.h>
++#include <linux/hash.h>
++#include <linux/module.h>
++#include <linux/htree_lock.h>
++
++enum {
++ HTREE_LOCK_BIT_EX = (1 << HTREE_LOCK_EX),
++ HTREE_LOCK_BIT_PW = (1 << HTREE_LOCK_PW),
++ HTREE_LOCK_BIT_PR = (1 << HTREE_LOCK_PR),
++ HTREE_LOCK_BIT_CW = (1 << HTREE_LOCK_CW),
++ HTREE_LOCK_BIT_CR = (1 << HTREE_LOCK_CR),
++};
++
++enum {
++ HTREE_LOCK_COMPAT_EX = 0,
++ HTREE_LOCK_COMPAT_PW = HTREE_LOCK_COMPAT_EX | HTREE_LOCK_BIT_CR,
++ HTREE_LOCK_COMPAT_PR = HTREE_LOCK_COMPAT_PW | HTREE_LOCK_BIT_PR,
++ HTREE_LOCK_COMPAT_CW = HTREE_LOCK_COMPAT_PW | HTREE_LOCK_BIT_CW,
++ HTREE_LOCK_COMPAT_CR = HTREE_LOCK_COMPAT_CW | HTREE_LOCK_BIT_PR |
++ HTREE_LOCK_BIT_PW,
++};
++
++static int htree_lock_compat[] = {
++ [HTREE_LOCK_EX] HTREE_LOCK_COMPAT_EX,
++ [HTREE_LOCK_PW] HTREE_LOCK_COMPAT_PW,
++ [HTREE_LOCK_PR] HTREE_LOCK_COMPAT_PR,
++ [HTREE_LOCK_CW] HTREE_LOCK_COMPAT_CW,
++ [HTREE_LOCK_CR] HTREE_LOCK_COMPAT_CR,
++};
++
++/* max allowed htree-lock depth.
++ * We only need depth=3 for ext4 although user can have higher value. */
++#define HTREE_LOCK_DEP_MAX 16
++
++#ifdef HTREE_LOCK_DEBUG
++
++static char *hl_name[] = {
++ [HTREE_LOCK_EX] "EX",
++ [HTREE_LOCK_PW] "PW",
++ [HTREE_LOCK_PR] "PR",
++ [HTREE_LOCK_CW] "CW",
++ [HTREE_LOCK_CR] "CR",
++};
++
++/* lock stats */
++struct htree_lock_node_stats {
++ unsigned long long blocked[HTREE_LOCK_MAX];
++ unsigned long long granted[HTREE_LOCK_MAX];
++ unsigned long long retried[HTREE_LOCK_MAX];
++ unsigned long long events;
++};
++
++struct htree_lock_stats {
++ struct htree_lock_node_stats nodes[HTREE_LOCK_DEP_MAX];
++ unsigned long long granted[HTREE_LOCK_MAX];
++ unsigned long long blocked[HTREE_LOCK_MAX];
++};
++
++static struct htree_lock_stats hl_stats;
++
++void htree_lock_stat_reset(void)
++{
++ memset(&hl_stats, 0, sizeof(hl_stats));
++}
++
++void htree_lock_stat_print(int depth)
++{
++ int i;
++ int j;
++
++ printk(KERN_DEBUG "HTREE LOCK STATS:\n");
++ for (i = 0; i < HTREE_LOCK_MAX; i++) {
++ printk(KERN_DEBUG "[%s]: G [%10llu], B [%10llu]\n",
++ hl_name[i], hl_stats.granted[i], hl_stats.blocked[i]);
++ }
++ for (i = 0; i < depth; i++) {
++ printk(KERN_DEBUG "HTREE CHILD [%d] STATS:\n", i);
++ for (j = 0; j < HTREE_LOCK_MAX; j++) {
++ printk(KERN_DEBUG
++ "[%s]: G [%10llu], B [%10llu], R [%10llu]\n",
++ hl_name[j], hl_stats.nodes[i].granted[j],
++ hl_stats.nodes[i].blocked[j],
++ hl_stats.nodes[i].retried[j]);
++ }
++ }
++}
++
++#define lk_grant_inc(m) do { hl_stats.granted[m]++; } while (0)
++#define lk_block_inc(m) do { hl_stats.blocked[m]++; } while (0)
++#define ln_grant_inc(d, m) do { hl_stats.nodes[d].granted[m]++; } while (0)
++#define ln_block_inc(d, m) do { hl_stats.nodes[d].blocked[m]++; } while (0)
++#define ln_retry_inc(d, m) do { hl_stats.nodes[d].retried[m]++; } while (0)
++#define ln_event_inc(d) do { hl_stats.nodes[d].events++; } while (0)
++
++#else /* !DEBUG */
++
++void htree_lock_stat_reset(void) {}
++void htree_lock_stat_print(int depth) {}
++
++#define lk_grant_inc(m) do {} while (0)
++#define lk_block_inc(m) do {} while (0)
++#define ln_grant_inc(d, m) do {} while (0)
++#define ln_block_inc(d, m) do {} while (0)
++#define ln_retry_inc(d, m) do {} while (0)
++#define ln_event_inc(d) do {} while (0)
++
++#endif /* DEBUG */
++
++EXPORT_SYMBOL(htree_lock_stat_reset);
++EXPORT_SYMBOL(htree_lock_stat_print);
++
++#define HTREE_DEP_ROOT (-1)
++
++#define htree_spin_lock(lhead, dep) \
++ bit_spin_lock((dep) + 1, &(lhead)->lh_lock)
++#define htree_spin_unlock(lhead, dep) \
++ bit_spin_unlock((dep) + 1, &(lhead)->lh_lock)
++
++#define htree_key_event_ignore(child, ln) \
++ (!((child)->lc_events & (1 << (ln)->ln_mode)))
++
++static int
++htree_key_list_empty(struct htree_lock_node *ln)
++{
++ return list_empty(&ln->ln_major_list) && list_empty(&ln->ln_minor_list);
++}
++
++static void
++htree_key_list_del_init(struct htree_lock_node *ln)
++{
++ struct htree_lock_node *tmp = NULL;
++
++ if (!list_empty(&ln->ln_minor_list)) {
++ tmp = list_entry(ln->ln_minor_list.next,
++ struct htree_lock_node, ln_minor_list);
++ list_del_init(&ln->ln_minor_list);
++ }
++
++ if (list_empty(&ln->ln_major_list))
++ return;
++
++ if (tmp == NULL) { /* not on minor key list */
++ list_del_init(&ln->ln_major_list);
++ } else {
++ BUG_ON(!list_empty(&tmp->ln_major_list));
++ list_replace_init(&ln->ln_major_list, &tmp->ln_major_list);
++ }
++}
++
++static void
++htree_key_list_replace_init(struct htree_lock_node *old,
++ struct htree_lock_node *new)
++{
++ if (!list_empty(&old->ln_major_list))
++ list_replace_init(&old->ln_major_list, &new->ln_major_list);
++
++ if (!list_empty(&old->ln_minor_list))
++ list_replace_init(&old->ln_minor_list, &new->ln_minor_list);
++}
++
++static void
++htree_key_event_enqueue(struct htree_lock_child *child,
++ struct htree_lock_node *ln, int dep, void *event)
++{
++ struct htree_lock_node *tmp;
++
++ /* NB: ALWAYS called holding lhead::lh_lock(dep) */
++ BUG_ON(ln->ln_mode == HTREE_LOCK_NL);
++ if (event == NULL || htree_key_event_ignore(child, ln))
++ return;
++
++ /* shouldn't be a very long list */
++ list_for_each_entry(tmp, &ln->ln_alive_list, ln_alive_list) {
++ if (tmp->ln_mode == HTREE_LOCK_NL) {
++ ln_event_inc(dep);
++ if (child->lc_callback != NULL)
++ child->lc_callback(tmp->ln_ev_target, event);
++ }
++ }
++}
++
++static int
++htree_node_lock_enqueue(struct htree_lock *newlk, struct htree_lock *curlk,
++ unsigned dep, int wait, void *event)
++{
++ struct htree_lock_child *child = &newlk->lk_head->lh_children[dep];
++ struct htree_lock_node *newln = &newlk->lk_nodes[dep];
++ struct htree_lock_node *curln = &curlk->lk_nodes[dep];
++
++ /* NB: ALWAYS called holding lhead::lh_lock(dep) */
++ /* NB: we only expect PR/PW lock mode at here, only these two modes are
++ * allowed for htree_node_lock(asserted in htree_node_lock_internal),
++ * NL is only used for listener, user can't directly require NL mode */
++ if ((curln->ln_mode == HTREE_LOCK_NL) ||
++ (curln->ln_mode != HTREE_LOCK_PW &&
++ newln->ln_mode != HTREE_LOCK_PW)) {
++ /* no conflict, attach it on granted list of @curlk */
++ if (curln->ln_mode != HTREE_LOCK_NL) {
++ list_add(&newln->ln_granted_list,
++ &curln->ln_granted_list);
++ } else {
++ /* replace key owner */
++ htree_key_list_replace_init(curln, newln);
++ }
++
++ list_add(&newln->ln_alive_list, &curln->ln_alive_list);
++ htree_key_event_enqueue(child, newln, dep, event);
++ ln_grant_inc(dep, newln->ln_mode);
++ return 1; /* still hold lh_lock */
++ }
++
++ if (!wait) { /* can't grant and don't want to wait */
++ ln_retry_inc(dep, newln->ln_mode);
++ newln->ln_mode = HTREE_LOCK_INVAL;
++ return -1; /* don't wait and just return -1 */
++ }
++
++ newlk->lk_task = current;
++ set_current_state(TASK_UNINTERRUPTIBLE);
++ /* conflict, attach it on blocked list of curlk */
++ list_add_tail(&newln->ln_blocked_list, &curln->ln_blocked_list);
++ list_add(&newln->ln_alive_list, &curln->ln_alive_list);
++ ln_block_inc(dep, newln->ln_mode);
++
++ htree_spin_unlock(newlk->lk_head, dep);
++ /* wait to be given the lock */
++ if (newlk->lk_task != NULL)
++ schedule();
++ /* granted, no doubt, wake up will set me RUNNING */
++ if (event == NULL || htree_key_event_ignore(child, newln))
++ return 0; /* granted without lh_lock */
++
++ htree_spin_lock(newlk->lk_head, dep);
++ htree_key_event_enqueue(child, newln, dep, event);
++ return 1; /* still hold lh_lock */
++}
++
++/*
++ * get PR/PW access to particular tree-node according to @dep and @key,
++ * it will return -1 if @wait is false and can't immediately grant this lock.
++ * All listeners(HTREE_LOCK_NL) on @dep and with the same @key will get
++ * @event if it's not NULL.
++ * NB: ALWAYS called holding lhead::lh_lock
++ */
++static int
++htree_node_lock_internal(struct htree_lock_head *lhead, struct htree_lock *lck,
++ htree_lock_mode_t mode, u32 key, unsigned dep,
++ int wait, void *event)
++{
++ LIST_HEAD(list);
++ struct htree_lock *tmp;
++ struct htree_lock *tmp2;
++ u16 major;
++ u16 minor;
++ u8 reverse;
++ u8 ma_bits;
++ u8 mi_bits;
++
++ BUG_ON(mode != HTREE_LOCK_PW && mode != HTREE_LOCK_PR);
++ BUG_ON(htree_node_is_granted(lck, dep));
++
++ key = hash_long(key, lhead->lh_hbits);
++
++ mi_bits = lhead->lh_hbits >> 1;
++ ma_bits = lhead->lh_hbits - mi_bits;
++
++ lck->lk_nodes[dep].ln_major_key = major = key & ((1U << ma_bits) - 1);
++ lck->lk_nodes[dep].ln_minor_key = minor = key >> ma_bits;
++ lck->lk_nodes[dep].ln_mode = mode;
++
++ /*
++ * The major key list is an ordered list, so searches are started
++ * at the end of the list that is numerically closer to major_key,
++ * so at most half of the list will be walked (for well-distributed
++ * keys). The list traversal aborts early if the expected key
++ * location is passed.
++ */
++ reverse = (major >= (1 << (ma_bits - 1)));
++
++ if (reverse) {
++ list_for_each_entry_reverse(tmp,
++ &lhead->lh_children[dep].lc_list,
++ lk_nodes[dep].ln_major_list) {
++ if (tmp->lk_nodes[dep].ln_major_key == major) {
++ goto search_minor;
++
++ } else if (tmp->lk_nodes[dep].ln_major_key < major) {
++ /* attach _after_ @tmp */
++ list_add(&lck->lk_nodes[dep].ln_major_list,
++ &tmp->lk_nodes[dep].ln_major_list);
++ goto out_grant_major;
++ }
++ }
++
++ list_add(&lck->lk_nodes[dep].ln_major_list,
++ &lhead->lh_children[dep].lc_list);
++ goto out_grant_major;
++
++ } else {
++ list_for_each_entry(tmp, &lhead->lh_children[dep].lc_list,
++ lk_nodes[dep].ln_major_list) {
++ if (tmp->lk_nodes[dep].ln_major_key == major) {
++ goto search_minor;
++
++ } else if (tmp->lk_nodes[dep].ln_major_key > major) {
++ /* insert _before_ @tmp */
++ list_add_tail(&lck->lk_nodes[dep].ln_major_list,
++ &tmp->lk_nodes[dep].ln_major_list);
++ goto out_grant_major;
++ }
++ }
++
++ list_add_tail(&lck->lk_nodes[dep].ln_major_list,
++ &lhead->lh_children[dep].lc_list);
++ goto out_grant_major;
++ }
++
++ search_minor:
++ /*
++ * NB: minor_key list doesn't have a "head", @list is just a
++ * temporary stub for helping list searching, make sure it's removed
++ * after searching.
++ * minor_key list is an ordered list too.
++ */
++ list_add_tail(&list, &tmp->lk_nodes[dep].ln_minor_list);
++
++ reverse = (minor >= (1 << (mi_bits - 1)));
++
++ if (reverse) {
++ list_for_each_entry_reverse(tmp2, &list,
++ lk_nodes[dep].ln_minor_list) {
++ if (tmp2->lk_nodes[dep].ln_minor_key == minor) {
++ goto out_enqueue;
++
++ } else if (tmp2->lk_nodes[dep].ln_minor_key < minor) {
++ /* attach _after_ @tmp2 */
++ list_add(&lck->lk_nodes[dep].ln_minor_list,
++ &tmp2->lk_nodes[dep].ln_minor_list);
++ goto out_grant_minor;
++ }
++ }
++
++ list_add(&lck->lk_nodes[dep].ln_minor_list, &list);
++
++ } else {
++ list_for_each_entry(tmp2, &list,
++ lk_nodes[dep].ln_minor_list) {
++ if (tmp2->lk_nodes[dep].ln_minor_key == minor) {
++ goto out_enqueue;
++
++ } else if (tmp2->lk_nodes[dep].ln_minor_key > minor) {
++ /* insert _before_ @tmp2 */
++ list_add_tail(&lck->lk_nodes[dep].ln_minor_list,
++ &tmp2->lk_nodes[dep].ln_minor_list);
++ goto out_grant_minor;
++ }
++ }
++
++ list_add_tail(&lck->lk_nodes[dep].ln_minor_list, &list);
++ }
++
++ out_grant_minor:
++ if (list.next == &lck->lk_nodes[dep].ln_minor_list) {
++ /* new lock @lck is the first one on minor_key list, which
++ * means it has the smallest minor_key and it should
++ * replace @tmp as minor_key owner */
++ list_replace_init(&tmp->lk_nodes[dep].ln_major_list,
++ &lck->lk_nodes[dep].ln_major_list);
++ }
++ /* remove the temporary head */
++ list_del(&list);
++
++ out_grant_major:
++ ln_grant_inc(dep, lck->lk_nodes[dep].ln_mode);
++ return 1; /* granted with holding lh_lock */
++
++ out_enqueue:
++ list_del(&list); /* remove temprary head */
++ return htree_node_lock_enqueue(lck, tmp2, dep, wait, event);
++}
++
++/*
++ * release the key of @lck at level @dep, and grant any blocked locks.
++ * caller will still listen on @key if @event is not NULL, which means
++ * caller can see a event (by event_cb) while granting any lock with
++ * the same key at level @dep.
++ * NB: ALWAYS called holding lhead::lh_lock
++ * NB: listener will not block anyone because listening mode is HTREE_LOCK_NL
++ */
++static void
++htree_node_unlock_internal(struct htree_lock_head *lhead,
++ struct htree_lock *curlk, unsigned dep, void *event)
++{
++ struct htree_lock_node *curln = &curlk->lk_nodes[dep];
++ struct htree_lock *grtlk = NULL;
++ struct htree_lock_node *grtln;
++ struct htree_lock *poslk;
++ struct htree_lock *tmplk;
++
++ if (!htree_node_is_granted(curlk, dep))
++ return;
++
++ if (!list_empty(&curln->ln_granted_list)) {
++ /* there is another granted lock */
++ grtlk = list_entry(curln->ln_granted_list.next,
++ struct htree_lock,
++ lk_nodes[dep].ln_granted_list);
++ list_del_init(&curln->ln_granted_list);
++ }
++
++ if (grtlk == NULL && !list_empty(&curln->ln_blocked_list)) {
++ /*
++ * @curlk is the only granted lock, so we confirmed:
++ * a) curln is key owner (attached on major/minor_list),
++ * so if there is any blocked lock, it should be attached
++ * on curln->ln_blocked_list
++ * b) we always can grant the first blocked lock
++ */
++ grtlk = list_entry(curln->ln_blocked_list.next,
++ struct htree_lock,
++ lk_nodes[dep].ln_blocked_list);
++ BUG_ON(grtlk->lk_task == NULL);
++ wake_up_process(grtlk->lk_task);
++ }
++
++ if (event != NULL &&
++ lhead->lh_children[dep].lc_events != HTREE_EVENT_DISABLE) {
++ curln->ln_ev_target = event;
++ curln->ln_mode = HTREE_LOCK_NL; /* listen! */
++ } else {
++ curln->ln_mode = HTREE_LOCK_INVAL;
++ }
++
++ if (grtlk == NULL) { /* I must be the only one locking this key */
++ struct htree_lock_node *tmpln;
++
++ BUG_ON(htree_key_list_empty(curln));
++
++ if (curln->ln_mode == HTREE_LOCK_NL) /* listening */
++ return;
++
++ /* not listening */
++ if (list_empty(&curln->ln_alive_list)) { /* no more listener */
++ htree_key_list_del_init(curln);
++ return;
++ }
++
++ tmpln = list_entry(curln->ln_alive_list.next,
++ struct htree_lock_node, ln_alive_list);
++
++ BUG_ON(tmpln->ln_mode != HTREE_LOCK_NL);
++
++ htree_key_list_replace_init(curln, tmpln);
++ list_del_init(&curln->ln_alive_list);
++
++ return;
++ }
++
++ /* have a granted lock */
++ grtln = &grtlk->lk_nodes[dep];
++ if (!list_empty(&curln->ln_blocked_list)) {
++ /* only key owner can be on both lists */
++ BUG_ON(htree_key_list_empty(curln));
++
++ if (list_empty(&grtln->ln_blocked_list)) {
++ list_add(&grtln->ln_blocked_list,
++ &curln->ln_blocked_list);
++ }
++ list_del_init(&curln->ln_blocked_list);
++ }
++ /*
++ * NB: this is the tricky part:
++ * We have only two modes for child-lock (PR and PW), also,
++ * only owner of the key (attached on major/minor_list) can be on
++ * both blocked_list and granted_list, so @grtlk must be one
++ * of these two cases:
++ *
++ * a) @grtlk is taken from granted_list, which means we've granted
++ * more than one lock so @grtlk has to be PR, the first blocked
++ * lock must be PW and we can't grant it at all.
++ * So even @grtlk is not owner of the key (empty blocked_list),
++ * we don't care because we can't grant any lock.
++ * b) we just grant a new lock which is taken from head of blocked
++ * list, and it should be the first granted lock, and it should
++ * be the first one linked on blocked_list.
++ *
++ * Either way, we can get correct result by iterating blocked_list
++ * of @grtlk, and don't have to bother on how to find out
++ * owner of current key.
++ */
++ list_for_each_entry_safe(poslk, tmplk, &grtln->ln_blocked_list,
++ lk_nodes[dep].ln_blocked_list) {
++ if (grtlk->lk_nodes[dep].ln_mode == HTREE_LOCK_PW ||
++ poslk->lk_nodes[dep].ln_mode == HTREE_LOCK_PW)
++ break;
++ /* grant all readers */
++ list_del_init(&poslk->lk_nodes[dep].ln_blocked_list);
++ list_add(&poslk->lk_nodes[dep].ln_granted_list,
++ &grtln->ln_granted_list);
++
++ BUG_ON(poslk->lk_task == NULL);
++ wake_up_process(poslk->lk_task);
++ }
++
++ /* if @curln is the owner of this key, replace it with @grtln */
++ if (!htree_key_list_empty(curln))
++ htree_key_list_replace_init(curln, grtln);
++
++ if (curln->ln_mode == HTREE_LOCK_INVAL)
++ list_del_init(&curln->ln_alive_list);
++}
++
++/*
++ * it's just wrapper of htree_node_lock_internal, it returns 1 on granted
++ * and 0 only if @wait is false and can't grant it immediately
++ */
++int
++htree_node_lock_try(struct htree_lock *lck, htree_lock_mode_t mode,
++ u32 key, unsigned dep, int wait, void *event)
++{
++ struct htree_lock_head *lhead = lck->lk_head;
++ int rc;
++
++ BUG_ON(dep >= lck->lk_depth);
++ BUG_ON(lck->lk_mode == HTREE_LOCK_INVAL);
++
++ htree_spin_lock(lhead, dep);
++ rc = htree_node_lock_internal(lhead, lck, mode, key, dep, wait, event);
++ if (rc != 0)
++ htree_spin_unlock(lhead, dep);
++ return rc >= 0;
++}
++EXPORT_SYMBOL(htree_node_lock_try);
++
++/* it's wrapper of htree_node_unlock_internal */
++void
++htree_node_unlock(struct htree_lock *lck, unsigned dep, void *event)
++{
++ struct htree_lock_head *lhead = lck->lk_head;
++
++ BUG_ON(dep >= lck->lk_depth);
++ BUG_ON(lck->lk_mode == HTREE_LOCK_INVAL);
++
++ htree_spin_lock(lhead, dep);
++ htree_node_unlock_internal(lhead, lck, dep, event);
++ htree_spin_unlock(lhead, dep);
++}
++EXPORT_SYMBOL(htree_node_unlock);
++
++/* stop listening on child-lock level @dep */
++void
++htree_node_stop_listen(struct htree_lock *lck, unsigned dep)
++{
++ struct htree_lock_node *ln = &lck->lk_nodes[dep];
++ struct htree_lock_node *tmp;
++
++ BUG_ON(htree_node_is_granted(lck, dep));
++ BUG_ON(!list_empty(&ln->ln_blocked_list));
++ BUG_ON(!list_empty(&ln->ln_granted_list));
++
++ if (!htree_node_is_listening(lck, dep))
++ return;
++
++ htree_spin_lock(lck->lk_head, dep);
++ ln->ln_mode = HTREE_LOCK_INVAL;
++ ln->ln_ev_target = NULL;
++
++ if (htree_key_list_empty(ln)) { /* not owner */
++ list_del_init(&ln->ln_alive_list);
++ goto out;
++ }
++
++ /* I'm the owner... */
++ if (list_empty(&ln->ln_alive_list)) { /* no more listener */
++ htree_key_list_del_init(ln);
++ goto out;
++ }
++
++ tmp = list_entry(ln->ln_alive_list.next,
++ struct htree_lock_node, ln_alive_list);
++
++ BUG_ON(tmp->ln_mode != HTREE_LOCK_NL);
++ htree_key_list_replace_init(ln, tmp);
++ list_del_init(&ln->ln_alive_list);
++ out:
++ htree_spin_unlock(lck->lk_head, dep);
++}
++EXPORT_SYMBOL(htree_node_stop_listen);
++
++/* release all child-locks if we have any */
++static void
++htree_node_release_all(struct htree_lock *lck)
++{
++ int i;
++
++ for (i = 0; i < lck->lk_depth; i++) {
++ if (htree_node_is_granted(lck, i))
++ htree_node_unlock(lck, i, NULL);
++ else if (htree_node_is_listening(lck, i))
++ htree_node_stop_listen(lck, i);
++ }
++}
++
++/*
++ * obtain htree lock, it could be blocked inside if there's conflict
++ * with any granted or blocked lock and @wait is true.
++ * NB: ALWAYS called holding lhead::lh_lock
++ */
++static int
++htree_lock_internal(struct htree_lock *lck, int wait)
++{
++ struct htree_lock_head *lhead = lck->lk_head;
++ int granted = 0;
++ int blocked = 0;
++ int i;
++
++ for (i = 0; i < HTREE_LOCK_MAX; i++) {
++ if (lhead->lh_ngranted[i] != 0)
++ granted |= 1 << i;
++ if (lhead->lh_nblocked[i] != 0)
++ blocked |= 1 << i;
++ }
++ if ((htree_lock_compat[lck->lk_mode] & granted) != granted ||
++ (htree_lock_compat[lck->lk_mode] & blocked) != blocked) {
++ /* will block current lock even it just conflicts with any
++ * other blocked lock, so lock like EX wouldn't starve */
++ if (!wait)
++ return -1;
++ lhead->lh_nblocked[lck->lk_mode]++;
++ lk_block_inc(lck->lk_mode);
++
++ lck->lk_task = current;
++ list_add_tail(&lck->lk_blocked_list, &lhead->lh_blocked_list);
++
++retry:
++ set_current_state(TASK_UNINTERRUPTIBLE);
++ htree_spin_unlock(lhead, HTREE_DEP_ROOT);
++ /* wait to be given the lock */
++ if (lck->lk_task != NULL)
++ schedule();
++ /* granted, no doubt. wake up will set me RUNNING.
++ * Since thread would be waken up accidentally,
++ * so we need check lock whether granted or not again. */
++ if (!list_empty(&lck->lk_blocked_list)) {
++ htree_spin_lock(lhead, HTREE_DEP_ROOT);
++ if (list_empty(&lck->lk_blocked_list)) {
++ htree_spin_unlock(lhead, HTREE_DEP_ROOT);
++ return 0;
++ }
++ goto retry;
++ }
++ return 0; /* without lh_lock */
++ }
++ lhead->lh_ngranted[lck->lk_mode]++;
++ lk_grant_inc(lck->lk_mode);
++ return 1;
++}
++
++/* release htree lock. NB: ALWAYS called holding lhead::lh_lock */
++static void
++htree_unlock_internal(struct htree_lock *lck)
++{
++ struct htree_lock_head *lhead = lck->lk_head;
++ struct htree_lock *tmp;
++ struct htree_lock *tmp2;
++ int granted = 0;
++ int i;
++
++ BUG_ON(lhead->lh_ngranted[lck->lk_mode] == 0);
++
++ lhead->lh_ngranted[lck->lk_mode]--;
++ lck->lk_mode = HTREE_LOCK_INVAL;
++
++ for (i = 0; i < HTREE_LOCK_MAX; i++) {
++ if (lhead->lh_ngranted[i] != 0)
++ granted |= 1 << i;
++ }
++ list_for_each_entry_safe(tmp, tmp2,
++ &lhead->lh_blocked_list, lk_blocked_list) {
++ /* conflict with any granted lock? */
++ if ((htree_lock_compat[tmp->lk_mode] & granted) != granted)
++ break;
++
++ list_del_init(&tmp->lk_blocked_list);
++
++ BUG_ON(lhead->lh_nblocked[tmp->lk_mode] == 0);
++
++ lhead->lh_nblocked[tmp->lk_mode]--;
++ lhead->lh_ngranted[tmp->lk_mode]++;
++ granted |= 1 << tmp->lk_mode;
++
++ BUG_ON(tmp->lk_task == NULL);
++ wake_up_process(tmp->lk_task);
++ }
++}
++
++/* it's wrapper of htree_lock_internal and exported interface.
++ * It always return 1 with granted lock if @wait is true, it can return 0
++ * if @wait is false and locking request can't be granted immediately */
++int
++htree_lock_try(struct htree_lock *lck, struct htree_lock_head *lhead,
++ htree_lock_mode_t mode, int wait)
++{
++ int rc;
++
++ BUG_ON(lck->lk_depth > lhead->lh_depth);
++ BUG_ON(lck->lk_head != NULL);
++ BUG_ON(lck->lk_task != NULL);
++
++ lck->lk_head = lhead;
++ lck->lk_mode = mode;
++
++ htree_spin_lock(lhead, HTREE_DEP_ROOT);
++ rc = htree_lock_internal(lck, wait);
++ if (rc != 0)
++ htree_spin_unlock(lhead, HTREE_DEP_ROOT);
++ return rc >= 0;
++}
++EXPORT_SYMBOL(htree_lock_try);
++
++/* it's wrapper of htree_unlock_internal and exported interface.
++ * It will release all htree_node_locks and htree_lock */
++void
++htree_unlock(struct htree_lock *lck)
++{
++ BUG_ON(lck->lk_head == NULL);
++ BUG_ON(lck->lk_mode == HTREE_LOCK_INVAL);
++
++ htree_node_release_all(lck);
++
++ htree_spin_lock(lck->lk_head, HTREE_DEP_ROOT);
++ htree_unlock_internal(lck);
++ htree_spin_unlock(lck->lk_head, HTREE_DEP_ROOT);
++ lck->lk_head = NULL;
++ lck->lk_task = NULL;
++}
++EXPORT_SYMBOL(htree_unlock);
++
++/* change lock mode */
++void
++htree_change_mode(struct htree_lock *lck, htree_lock_mode_t mode)
++{
++ BUG_ON(lck->lk_mode == HTREE_LOCK_INVAL);
++ lck->lk_mode = mode;
++}
++EXPORT_SYMBOL(htree_change_mode);
++
++/* release htree lock, and lock it again with new mode.
++ * This function will first release all htree_node_locks and htree_lock,
++ * then try to gain htree_lock with new @mode.
++ * It always return 1 with granted lock if @wait is true, it can return 0
++ * if @wait is false and locking request can't be granted immediately */
++int
++htree_change_lock_try(struct htree_lock *lck, htree_lock_mode_t mode, int wait)
++{
++ struct htree_lock_head *lhead = lck->lk_head;
++ int rc;
++
++ BUG_ON(lhead == NULL);
++ BUG_ON(lck->lk_mode == mode);
++ BUG_ON(lck->lk_mode == HTREE_LOCK_INVAL || mode == HTREE_LOCK_INVAL);
++
++ htree_node_release_all(lck);
++
++ htree_spin_lock(lhead, HTREE_DEP_ROOT);
++ htree_unlock_internal(lck);
++ lck->lk_mode = mode;
++ rc = htree_lock_internal(lck, wait);
++ if (rc != 0)
++ htree_spin_unlock(lhead, HTREE_DEP_ROOT);
++ return rc >= 0;
++}
++EXPORT_SYMBOL(htree_change_lock_try);
++
++/* create a htree_lock head with @depth levels (number of child-locks),
++ * it is a per resoruce structure */
++struct htree_lock_head *
++htree_lock_head_alloc(unsigned depth, unsigned hbits, unsigned priv)
++{
++ struct htree_lock_head *lhead;
++ int i;
++
++ if (depth > HTREE_LOCK_DEP_MAX) {
++ printk(KERN_ERR "%d is larger than max htree_lock depth %d\n",
++ depth, HTREE_LOCK_DEP_MAX);
++ return NULL;
++ }
++
++ lhead = kzalloc(offsetof(struct htree_lock_head,
++ lh_children[depth]) + priv, GFP_NOFS);
++ if (lhead == NULL)
++ return NULL;
++
++ if (hbits < HTREE_HBITS_MIN)
++ lhead->lh_hbits = HTREE_HBITS_MIN;
++ else if (hbits > HTREE_HBITS_MAX)
++ lhead->lh_hbits = HTREE_HBITS_MAX;
++
++ lhead->lh_lock = 0;
++ lhead->lh_depth = depth;
++ INIT_LIST_HEAD(&lhead->lh_blocked_list);
++ if (priv > 0) {
++ lhead->lh_private = (void *)lhead +
++ offsetof(struct htree_lock_head, lh_children[depth]);
++ }
++
++ for (i = 0; i < depth; i++) {
++ INIT_LIST_HEAD(&lhead->lh_children[i].lc_list);
++ lhead->lh_children[i].lc_events = HTREE_EVENT_DISABLE;
++ }
++ return lhead;
++}
++EXPORT_SYMBOL(htree_lock_head_alloc);
++
++/* free the htree_lock head */
++void
++htree_lock_head_free(struct htree_lock_head *lhead)
++{
++ int i;
++
++ BUG_ON(!list_empty(&lhead->lh_blocked_list));
++ for (i = 0; i < lhead->lh_depth; i++)
++ BUG_ON(!list_empty(&lhead->lh_children[i].lc_list));
++ kfree(lhead);
++}
++EXPORT_SYMBOL(htree_lock_head_free);
++
++/* register event callback for @events of child-lock at level @dep */
++void
++htree_lock_event_attach(struct htree_lock_head *lhead, unsigned dep,
++ unsigned events, htree_event_cb_t callback)
++{
++ BUG_ON(lhead->lh_depth <= dep);
++ lhead->lh_children[dep].lc_events = events;
++ lhead->lh_children[dep].lc_callback = callback;
++}
++EXPORT_SYMBOL(htree_lock_event_attach);
++
++/* allocate a htree_lock, which is per-thread structure, @pbytes is some
++ * extra-bytes as private data for caller */
++struct htree_lock *
++htree_lock_alloc(unsigned depth, unsigned pbytes)
++{
++ struct htree_lock *lck;
++ int i = offsetof(struct htree_lock, lk_nodes[depth]);
++
++ if (depth > HTREE_LOCK_DEP_MAX) {
++ printk(KERN_ERR "%d is larger than max htree_lock depth %d\n",
++ depth, HTREE_LOCK_DEP_MAX);
++ return NULL;
++ }
++ lck = kzalloc(i + pbytes, GFP_NOFS);
++ if (lck == NULL)
++ return NULL;
++
++ if (pbytes != 0)
++ lck->lk_private = (void *)lck + i;
++ lck->lk_mode = HTREE_LOCK_INVAL;
++ lck->lk_depth = depth;
++ INIT_LIST_HEAD(&lck->lk_blocked_list);
++
++ for (i = 0; i < depth; i++) {
++ struct htree_lock_node *node = &lck->lk_nodes[i];
++
++ node->ln_mode = HTREE_LOCK_INVAL;
++ INIT_LIST_HEAD(&node->ln_major_list);
++ INIT_LIST_HEAD(&node->ln_minor_list);
++ INIT_LIST_HEAD(&node->ln_alive_list);
++ INIT_LIST_HEAD(&node->ln_blocked_list);
++ INIT_LIST_HEAD(&node->ln_granted_list);
++ }
++
++ return lck;
++}
++EXPORT_SYMBOL(htree_lock_alloc);
++
++/* free htree_lock node */
++void
++htree_lock_free(struct htree_lock *lck)
++{
++ BUG_ON(lck->lk_mode != HTREE_LOCK_INVAL);
++ kfree(lck);
++}
++EXPORT_SYMBOL(htree_lock_free);
+Index: linux-4.18.0-80.1.2.el8_0/fs/ext4/namei.c
+===================================================================
+--- linux-4.18.0-80.1.2.el8_0.orig/fs/ext4/namei.c
++++ linux-4.18.0-80.1.2.el8_0/fs/ext4/namei.c
+@@ -54,6 +54,7 @@ struct buffer_head *ext4_append(handle_t
+ ext4_lblk_t *block)
+ {
+ struct buffer_head *bh;
++ struct ext4_inode_info *ei = EXT4_I(inode);
+ int err;
+
+ if (unlikely(EXT4_SB(inode->i_sb)->s_max_dir_size_kb &&
+@@ -61,15 +62,22 @@ struct buffer_head *ext4_append(handle_t
+ EXT4_SB(inode->i_sb)->s_max_dir_size_kb)))
+ return ERR_PTR(-ENOSPC);
+
++ /* with parallel dir operations all appends
++ * have to be serialized -bzzz */
++ down(&ei->i_append_sem);
++
+ *block = inode->i_size >> inode->i_sb->s_blocksize_bits;
+
+ bh = ext4_bread(handle, inode, *block, EXT4_GET_BLOCKS_CREATE);
+- if (IS_ERR(bh))
++ if (IS_ERR(bh)) {
++ up(&ei->i_append_sem);
+ return bh;
++ }
+ inode->i_size += inode->i_sb->s_blocksize;
+ EXT4_I(inode)->i_disksize = inode->i_size;
+ BUFFER_TRACE(bh, "get_write_access");
+ err = ext4_journal_get_write_access(handle, bh);
++ up(&ei->i_append_sem);
+ if (err) {
+ brelse(bh);
+ ext4_std_error(inode->i_sb, err);
+@@ -250,7 +258,8 @@ static unsigned dx_node_limit(struct ino
+ static struct dx_frame *dx_probe(struct ext4_filename *fname,
+ struct inode *dir,
+ struct dx_hash_info *hinfo,
+- struct dx_frame *frame);
++ struct dx_frame *frame,
++ struct htree_lock *lck);
+ static void dx_release(struct dx_frame *frames);
+ static int dx_make_map(struct inode *dir, struct ext4_dir_entry_2 *de,
+ unsigned blocksize, struct dx_hash_info *hinfo,
+@@ -264,12 +273,13 @@ static void dx_insert_block(struct dx_fr
+ static int ext4_htree_next_block(struct inode *dir, __u32 hash,
+ struct dx_frame *frame,
+ struct dx_frame *frames,
+- __u32 *start_hash);
++ __u32 *start_hash, struct htree_lock *lck);
+ static struct buffer_head * ext4_dx_find_entry(struct inode *dir,
+ struct ext4_filename *fname,
+- struct ext4_dir_entry_2 **res_dir);
++ struct ext4_dir_entry_2 **res_dir, struct htree_lock *lck);
+ static int ext4_dx_add_entry(handle_t *handle, struct ext4_filename *fname,
+- struct inode *dir, struct inode *inode);
++ struct inode *dir, struct inode *inode,
++ struct htree_lock *lck);
+
+ /* checksumming functions */
+ void initialize_dirent_tail(struct ext4_dir_entry_tail *t,
+@@ -733,6 +743,227 @@ struct stats dx_show_entries(struct dx_h
+ }
+ #endif /* DX_DEBUG */
+
++/* private data for htree_lock */
++struct ext4_dir_lock_data {
++ unsigned ld_flags; /* bits-map for lock types */
++ unsigned ld_count; /* # entries of the last DX block */
++ struct dx_entry ld_at_entry; /* copy of leaf dx_entry */
++ struct dx_entry *ld_at; /* position of leaf dx_entry */
++};
++
++#define ext4_htree_lock_data(l) ((struct ext4_dir_lock_data *)(l)->lk_private)
++#define ext4_find_entry(dir, name, dirent, inline) \
++ __ext4_find_entry(dir, name, dirent, inline, NULL)
++#define ext4_add_entry(handle, dentry, inode) \
++ __ext4_add_entry(handle, dentry, inode, NULL)
++
++/* NB: ext4_lblk_t is 32 bits so we use high bits to identify invalid blk */
++#define EXT4_HTREE_NODE_CHANGED (0xcafeULL << 32)
++
++static void ext4_htree_event_cb(void *target, void *event)
++{
++ u64 *block = (u64 *)target;
++
++ if (*block == dx_get_block((struct dx_entry *)event))
++ *block = EXT4_HTREE_NODE_CHANGED;
++}
++
++struct htree_lock_head *ext4_htree_lock_head_alloc(unsigned hbits)
++{
++ struct htree_lock_head *lhead;
++
++ lhead = htree_lock_head_alloc(EXT4_LK_MAX, hbits, 0);
++ if (lhead != NULL) {
++ htree_lock_event_attach(lhead, EXT4_LK_SPIN, HTREE_EVENT_WR,
++ ext4_htree_event_cb);
++ }
++ return lhead;
++}
++EXPORT_SYMBOL(ext4_htree_lock_head_alloc);
++
++struct htree_lock *ext4_htree_lock_alloc(void)
++{
++ return htree_lock_alloc(EXT4_LK_MAX,
++ sizeof(struct ext4_dir_lock_data));
++}
++EXPORT_SYMBOL(ext4_htree_lock_alloc);
++
++static htree_lock_mode_t ext4_htree_mode(unsigned flags)
++{
++ switch (flags) {
++ default: /* 0 or unknown flags require EX lock */
++ return HTREE_LOCK_EX;
++ case EXT4_HLOCK_READDIR:
++ return HTREE_LOCK_PR;
++ case EXT4_HLOCK_LOOKUP:
++ return HTREE_LOCK_CR;
++ case EXT4_HLOCK_DEL:
++ case EXT4_HLOCK_ADD:
++ return HTREE_LOCK_CW;
++ }
++}
++
++/* return PR for read-only operations, otherwise return EX */
++static inline htree_lock_mode_t ext4_htree_safe_mode(unsigned flags)
++{
++ int writer = (flags & EXT4_LB_DE) == EXT4_LB_DE;
++
++ /* 0 requires EX lock */
++ return (flags == 0 || writer) ? HTREE_LOCK_EX : HTREE_LOCK_PR;
++}
++
++static int ext4_htree_safe_locked(struct htree_lock *lck)
++{
++ int writer;
++
++ if (lck == NULL || lck->lk_mode == HTREE_LOCK_EX)
++ return 1;
++
++ writer = (ext4_htree_lock_data(lck)->ld_flags & EXT4_LB_DE) ==
++ EXT4_LB_DE;
++ if (writer) /* all readers & writers are excluded? */
++ return lck->lk_mode == HTREE_LOCK_EX;
++
++ /* all writers are excluded? */
++ return lck->lk_mode == HTREE_LOCK_PR ||
++ lck->lk_mode == HTREE_LOCK_PW ||
++ lck->lk_mode == HTREE_LOCK_EX;
++}
++
++/* relock htree_lock with EX mode if it's change operation, otherwise
++ * relock it with PR mode. It's noop if PDO is disabled. */
++static void ext4_htree_safe_relock(struct htree_lock *lck)
++{
++ if (!ext4_htree_safe_locked(lck)) {
++ unsigned flags = ext4_htree_lock_data(lck)->ld_flags;
++
++ htree_change_lock(lck, ext4_htree_safe_mode(flags));
++ }
++}
++
++void ext4_htree_lock(struct htree_lock *lck, struct htree_lock_head *lhead,
++ struct inode *dir, unsigned flags)
++{
++ htree_lock_mode_t mode = is_dx(dir) ? ext4_htree_mode(flags) :
++ ext4_htree_safe_mode(flags);
++
++ ext4_htree_lock_data(lck)->ld_flags = flags;
++ htree_lock(lck, lhead, mode);
++ if (!is_dx(dir))
++ ext4_htree_safe_relock(lck); /* make sure it's safe locked */
++}
++EXPORT_SYMBOL(ext4_htree_lock);
++
++static int ext4_htree_node_lock(struct htree_lock *lck, struct dx_entry *at,
++ unsigned lmask, int wait, void *ev)
++{
++ u32 key = (at == NULL) ? 0 : dx_get_block(at);
++ u32 mode;
++
++ /* NOOP if htree is well protected or caller doesn't require the lock */
++ if (ext4_htree_safe_locked(lck) ||
++ !(ext4_htree_lock_data(lck)->ld_flags & lmask))
++ return 1;
++
++ mode = (ext4_htree_lock_data(lck)->ld_flags & lmask) == lmask ?
++ HTREE_LOCK_PW : HTREE_LOCK_PR;
++ while (1) {
++ if (htree_node_lock_try(lck, mode, key, ffz(~lmask), wait, ev))
++ return 1;
++ if (!(lmask & EXT4_LB_SPIN)) /* not a spinlock */
++ return 0;
++ cpu_relax(); /* spin until granted */
++ }
++}
++
++static int ext4_htree_node_locked(struct htree_lock *lck, unsigned lmask)
++{
++ return ext4_htree_safe_locked(lck) ||
++ htree_node_is_granted(lck, ffz(~lmask));
++}
++
++static void ext4_htree_node_unlock(struct htree_lock *lck,
++ unsigned lmask, void *buf)
++{
++ /* NB: it's safe to call mutiple times or even it's not locked */
++ if (!ext4_htree_safe_locked(lck) &&
++ htree_node_is_granted(lck, ffz(~lmask)))
++ htree_node_unlock(lck, ffz(~lmask), buf);
++}
++
++#define ext4_htree_dx_lock(lck, key) \
++ ext4_htree_node_lock(lck, key, EXT4_LB_DX, 1, NULL)
++#define ext4_htree_dx_lock_try(lck, key) \
++ ext4_htree_node_lock(lck, key, EXT4_LB_DX, 0, NULL)
++#define ext4_htree_dx_unlock(lck) \
++ ext4_htree_node_unlock(lck, EXT4_LB_DX, NULL)
++#define ext4_htree_dx_locked(lck) \
++ ext4_htree_node_locked(lck, EXT4_LB_DX)
++
++static void ext4_htree_dx_need_lock(struct htree_lock *lck)
++{
++ struct ext4_dir_lock_data *ld;
++
++ if (ext4_htree_safe_locked(lck))
++ return;
++
++ ld = ext4_htree_lock_data(lck);
++ switch (ld->ld_flags) {
++ default:
++ return;
++ case EXT4_HLOCK_LOOKUP:
++ ld->ld_flags = EXT4_HLOCK_LOOKUP_SAFE;
++ return;
++ case EXT4_HLOCK_DEL:
++ ld->ld_flags = EXT4_HLOCK_DEL_SAFE;
++ return;
++ case EXT4_HLOCK_ADD:
++ ld->ld_flags = EXT4_HLOCK_SPLIT;
++ return;
++ }
++}
++
++#define ext4_htree_de_lock(lck, key) \
++ ext4_htree_node_lock(lck, key, EXT4_LB_DE, 1, NULL)
++#define ext4_htree_de_unlock(lck) \
++ ext4_htree_node_unlock(lck, EXT4_LB_DE, NULL)
++
++#define ext4_htree_spin_lock(lck, key, event) \
++ ext4_htree_node_lock(lck, key, EXT4_LB_SPIN, 0, event)
++#define ext4_htree_spin_unlock(lck) \
++ ext4_htree_node_unlock(lck, EXT4_LB_SPIN, NULL)
++#define ext4_htree_spin_unlock_listen(lck, p) \
++ ext4_htree_node_unlock(lck, EXT4_LB_SPIN, p)
++
++static void ext4_htree_spin_stop_listen(struct htree_lock *lck)
++{
++ if (!ext4_htree_safe_locked(lck) &&
++ htree_node_is_listening(lck, ffz(~EXT4_LB_SPIN)))
++ htree_node_stop_listen(lck, ffz(~EXT4_LB_SPIN));
++}
++
++enum {
++ DX_HASH_COL_IGNORE, /* ignore collision while probing frames */
++ DX_HASH_COL_YES, /* there is collision and it does matter */
++ DX_HASH_COL_NO, /* there is no collision */
++};
++
++static int dx_probe_hash_collision(struct htree_lock *lck,
++ struct dx_entry *entries,
++ struct dx_entry *at, u32 hash)
++{
++ if (!(lck && ext4_htree_lock_data(lck)->ld_flags & EXT4_LB_EXACT)) {
++ return DX_HASH_COL_IGNORE; /* don't care about collision */
++
++ } else if (at == entries + dx_get_count(entries) - 1) {
++ return DX_HASH_COL_IGNORE; /* not in any leaf of this DX */
++
++ } else { /* hash collision? */
++ return ((dx_get_hash(at + 1) & ~1) == hash) ?
++ DX_HASH_COL_YES : DX_HASH_COL_NO;
++ }
++}
++
+ /*
+ * Probe for a directory leaf block to search.
+ *
+@@ -744,10 +975,11 @@ struct stats dx_show_entries(struct dx_h
+ */
+ static struct dx_frame *
+ dx_probe(struct ext4_filename *fname, struct inode *dir,
+- struct dx_hash_info *hinfo, struct dx_frame *frame_in)
++ struct dx_hash_info *hinfo, struct dx_frame *frame_in,
++ struct htree_lock *lck)
+ {
+ unsigned count, indirect;
+- struct dx_entry *at, *entries, *p, *q, *m;
++ struct dx_entry *at, *entries, *p, *q, *m, *dx = NULL;
+ struct dx_root_info *info;
+ struct dx_frame *frame = frame_in;
+ struct dx_frame *ret_err = ERR_PTR(ERR_BAD_DX_DIR);
+@@ -809,8 +1041,15 @@ dx_probe(struct ext4_filename *fname, st
+
+ dxtrace(printk("Look up %x", hash));
+ while (1) {
++ if (indirect == 0) { /* the last index level */
++ /* NB: ext4_htree_dx_lock() could be noop if
++ * DX-lock flag is not set for current operation */
++ ext4_htree_dx_lock(lck, dx);
++ ext4_htree_spin_lock(lck, dx, NULL);
++ }
+ count = dx_get_count(entries);
+- if (!count || count > dx_get_limit(entries)) {
++ if (count == 0 || count > dx_get_limit(entries)) {
++ ext4_htree_spin_unlock(lck); /* release spin */
+ ext4_warning_inode(dir,
+ "dx entry: count %u beyond limit %u",
+ count, dx_get_limit(entries));
+@@ -849,8 +1088,70 @@ dx_probe(struct ext4_filename *fname, st
+ dx_get_block(at)));
+ frame->entries = entries;
+ frame->at = at;
+- if (!indirect--)
++
++ if (indirect == 0) { /* the last index level */
++ struct ext4_dir_lock_data *ld;
++ u64 myblock;
++
++ /* By default we only lock DE-block, however, we will
++ * also lock the last level DX-block if:
++ * a) there is hash collision
++ * we will set DX-lock flag (a few lines below)
++ * and redo to lock DX-block
++ * see detail in dx_probe_hash_collision()
++ * b) it's a retry from splitting
++ * we need to lock the last level DX-block so nobody
++ * else can split any leaf blocks under the same
++ * DX-block, see detail in ext4_dx_add_entry()
++ */
++ if (ext4_htree_dx_locked(lck)) {
++ /* DX-block is locked, just lock DE-block
++ * and return */
++ ext4_htree_spin_unlock(lck);
++ if (!ext4_htree_safe_locked(lck))
++ ext4_htree_de_lock(lck, frame->at);
++ return frame;
++ }
++ /* it's pdirop and no DX lock */
++ if (dx_probe_hash_collision(lck, entries, at, hash) ==
++ DX_HASH_COL_YES) {
++ /* found hash collision, set DX-lock flag
++ * and retry to abtain DX-lock */
++ ext4_htree_spin_unlock(lck);
++ ext4_htree_dx_need_lock(lck);
++ continue;
++ }
++ ld = ext4_htree_lock_data(lck);
++ /* because I don't lock DX, so @at can't be trusted
++ * after I release spinlock so I have to save it */
++ ld->ld_at = at;
++ ld->ld_at_entry = *at;
++ ld->ld_count = dx_get_count(entries);
++
++ frame->at = &ld->ld_at_entry;
++ myblock = dx_get_block(at);
++
++ /* NB: ordering locking */
++ ext4_htree_spin_unlock_listen(lck, &myblock);
++ /* other thread can split this DE-block because:
++ * a) I don't have lock for the DE-block yet
++ * b) I released spinlock on DX-block
++ * if it happened I can detect it by listening
++ * splitting event on this DE-block */
++ ext4_htree_de_lock(lck, frame->at);
++ ext4_htree_spin_stop_listen(lck);
++
++ if (myblock == EXT4_HTREE_NODE_CHANGED) {
++ /* someone split this DE-block before
++ * I locked it, I need to retry and lock
++ * valid DE-block */
++ ext4_htree_de_unlock(lck);
++ continue;
++ }
+ return frame;
++ }
++ dx = at;
++ indirect--;
+ frame++;
+ frame->bh = ext4_read_dirblock(dir, dx_get_block(at), INDEX);
+ if (IS_ERR(frame->bh)) {
+@@ -916,7 +1217,7 @@ static void dx_release(struct dx_frame *
+ static int ext4_htree_next_block(struct inode *dir, __u32 hash,
+ struct dx_frame *frame,
+ struct dx_frame *frames,
+- __u32 *start_hash)
++ __u32 *start_hash, struct htree_lock *lck)
+ {
+ struct dx_frame *p;
+ struct buffer_head *bh;
+@@ -931,12 +1232,22 @@ static int ext4_htree_next_block(struct
+ * this loop, num_frames indicates the number of interior
+ * nodes need to be read.
+ */
++ ext4_htree_de_unlock(lck);
+ while (1) {
+- if (++(p->at) < p->entries + dx_get_count(p->entries))
+- break;
++ if (num_frames > 0 || ext4_htree_dx_locked(lck)) {
++ /* num_frames > 0 :
++ * DX block
++ * ext4_htree_dx_locked:
++ * frame->at is reliable pointer returned by dx_probe,
++ * otherwise dx_probe already knew no collision */
++ if (++(p->at) < p->entries + dx_get_count(p->entries))
++ break;
++ }
+ if (p == frames)
+ return 0;
+ num_frames++;
++ if (num_frames == 1)
++ ext4_htree_dx_unlock(lck);
+ p--;
+ }
+
+@@ -959,6 +1270,13 @@ static int ext4_htree_next_block(struct
+ * block so no check is necessary
+ */
+ while (num_frames--) {
++ if (num_frames == 0) {
++ /* it's not always necessary, we just don't want to
++ * detect hash collision again */
++ ext4_htree_dx_need_lock(lck);
++ ext4_htree_dx_lock(lck, p->at);
++ }
++
+ bh = ext4_read_dirblock(dir, dx_get_block(p->at), INDEX);
+ if (IS_ERR(bh))
+ return PTR_ERR(bh);
+@@ -967,6 +1285,7 @@ static int ext4_htree_next_block(struct
+ p->bh = bh;
+ p->at = p->entries = ((struct dx_node *) bh->b_data)->entries;
+ }
++ ext4_htree_de_lock(lck, p->at);
+ return 1;
+ }
+
+@@ -1114,10 +1433,10 @@ int ext4_htree_fill_tree(struct file *di
+ }
+ hinfo.hash = start_hash;
+ hinfo.minor_hash = 0;
+- frame = dx_probe(NULL, dir, &hinfo, frames);
++ /* assume it's PR locked */
++ frame = dx_probe(NULL, dir, &hinfo, frames, NULL);
+ if (IS_ERR(frame))
+ return PTR_ERR(frame);
+-
+ /* Add '.' and '..' from the htree header */
+ if (!start_hash && !start_minor_hash) {
+ de = (struct ext4_dir_entry_2 *) frames[0].bh->b_data;
+@@ -1157,7 +1476,7 @@ int ext4_htree_fill_tree(struct file *di
+ count += ret;
+ hashval = ~0;
+ ret = ext4_htree_next_block(dir, HASH_NB_ALWAYS,
+- frame, frames, &hashval);
++ frame, frames, &hashval, NULL);
+ *next_hash = hashval;
+ if (ret < 0) {
+ err = ret;
+@@ -1349,10 +1668,10 @@ static int is_dx_internal_node(struct in
+ * The returned buffer_head has ->b_count elevated. The caller is expected
+ * to brelse() it when appropriate.
+ */
+-static struct buffer_head * ext4_find_entry (struct inode *dir,
++struct buffer_head *__ext4_find_entry(struct inode *dir,
+ const struct qstr *d_name,
+ struct ext4_dir_entry_2 **res_dir,
+- int *inlined)
++ int *inlined, struct htree_lock *lck)
+ {
+ struct super_block *sb;
+ struct buffer_head *bh_use[NAMEI_RA_SIZE];
+@@ -1401,7 +1720,7 @@ static struct buffer_head * ext4_find_en
+ goto restart;
+ }
+ if (is_dx(dir)) {
+- ret = ext4_dx_find_entry(dir, &fname, res_dir);
++ ret = ext4_dx_find_entry(dir, &fname, res_dir, lck);
+ /*
+ * On success, or if the error was file not found,
+ * return. Otherwise, fall back to doing a search the
+@@ -1411,6 +1730,7 @@ static struct buffer_head * ext4_find_en
+ goto cleanup_and_exit;
+ dxtrace(printk(KERN_DEBUG "ext4_find_entry: dx failed, "
+ "falling back\n"));
++ ext4_htree_safe_relock(lck);
+ ret = NULL;
+ }
+ nblocks = dir->i_size >> EXT4_BLOCK_SIZE_BITS(sb);
+@@ -1499,10 +1819,12 @@ cleanup_and_exit:
+ ext4_fname_free_filename(&fname);
+ return ret;
+ }
++EXPORT_SYMBOL(__ext4_find_entry);
+
+ static struct buffer_head * ext4_dx_find_entry(struct inode *dir,
+ struct ext4_filename *fname,
+- struct ext4_dir_entry_2 **res_dir)
++ struct ext4_dir_entry_2 **res_dir,
++ struct htree_lock *lck)
+ {
+ struct super_block * sb = dir->i_sb;
+ struct dx_frame frames[EXT4_HTREE_LEVEL], *frame;
+@@ -1513,7 +1835,7 @@ static struct buffer_head * ext4_dx_find
+ #ifdef CONFIG_EXT4_FS_ENCRYPTION
+ *res_dir = NULL;
+ #endif
+- frame = dx_probe(fname, dir, NULL, frames);
++ frame = dx_probe(fname, dir, NULL, frames, lck);
+ if (IS_ERR(frame))
+ return (struct buffer_head *) frame;
+ do {
+@@ -1535,7 +1857,7 @@ static struct buffer_head * ext4_dx_find
+
+ /* Check to see if we should continue to search */
+ retval = ext4_htree_next_block(dir, fname->hinfo.hash, frame,
+- frames, NULL);
++ frames, NULL, lck);
+ if (retval < 0) {
+ ext4_warning_inode(dir,
+ "error %d reading directory index block",
+@@ -1710,8 +2032,9 @@ static struct ext4_dir_entry_2* dx_pack_
+ * Returns pointer to de in block into which the new entry will be inserted.
+ */
+ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir,
+- struct buffer_head **bh,struct dx_frame *frame,
+- struct dx_hash_info *hinfo)
++ struct buffer_head **bh, struct dx_frame *frames,
++ struct dx_frame *frame, struct dx_hash_info *hinfo,
++ struct htree_lock *lck)
+ {
+ unsigned blocksize = dir->i_sb->s_blocksize;
+ unsigned count, continued;
+@@ -1773,8 +2096,14 @@ static struct ext4_dir_entry_2 *do_split
+ hash2, split, count-split));
+
+ /* Fancy dance to stay within two buffers */
+- de2 = dx_move_dirents(data1, data2, map + split, count - split,
+- blocksize);
++ if (hinfo->hash < hash2) {
++ de2 = dx_move_dirents(data1, data2, map + split,
++ count - split, blocksize);
++ } else {
++ /* make sure we will add entry to the same block which
++ * we have already locked */
++ de2 = dx_move_dirents(data1, data2, map, split, blocksize);
++ }
+ de = dx_pack_dirents(data1, blocksize);
+ de->rec_len = ext4_rec_len_to_disk(data1 + (blocksize - csum_size) -
+ (char *) de,
+@@ -1795,12 +2124,21 @@ static struct ext4_dir_entry_2 *do_split
+ dxtrace(dx_show_leaf(dir, hinfo, (struct ext4_dir_entry_2 *) data2,
+ blocksize, 1));
+
+- /* Which block gets the new entry? */
+- if (hinfo->hash >= hash2) {
+- swap(*bh, bh2);
+- de = de2;
++ ext4_htree_spin_lock(lck, frame > frames ? (frame - 1)->at : NULL,
++ frame->at); /* notify block is being split */
++ if (hinfo->hash < hash2) {
++ dx_insert_block(frame, hash2 + continued, newblock);
++
++ } else {
++ /* switch block number */
++ dx_insert_block(frame, hash2 + continued,
++ dx_get_block(frame->at));
++ dx_set_block(frame->at, newblock);
++ (frame->at)++;
+ }
+- dx_insert_block(frame, hash2 + continued, newblock);
++ ext4_htree_spin_unlock(lck);
++ ext4_htree_dx_unlock(lck);
++
+ err = ext4_handle_dirty_dirent_node(handle, dir, bh2);
+ if (err)
+ goto journal_error;
+@@ -2074,7 +2412,7 @@ static int make_indexed_dir(handle_t *ha
+ if (retval)
+ goto out_frames;
+
+- de = do_split(handle,dir, &bh2, frame, &fname->hinfo);
++ de = do_split(handle, dir, &bh2, frames, frame, &fname->hinfo, NULL);
+ if (IS_ERR(de)) {
+ retval = PTR_ERR(de);
+ goto out_frames;
+@@ -2184,8 +2522,8 @@ out:
+ * may not sleep between calling this and putting something into
+ * the entry, as someone else might have used it while you slept.
+ */
+-static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
+- struct inode *inode)
++int __ext4_add_entry(handle_t *handle, struct dentry *dentry,
++ struct inode *inode, struct htree_lock *lck)
+ {
+ struct inode *dir = d_inode(dentry->d_parent);
+ struct buffer_head *bh = NULL;
+@@ -2226,9 +2564,10 @@ static int ext4_add_entry(handle_t *hand
+ if (dentry->d_name.len == 2 &&
+ memcmp(dentry->d_name.name, "..", 2) == 0)
+ return ext4_update_dotdot(handle, dentry, inode);
+- retval = ext4_dx_add_entry(handle, &fname, dir, inode);
++ retval = ext4_dx_add_entry(handle, &fname, dir, inode, lck);
+ if (!retval || (retval != ERR_BAD_DX_DIR))
+ goto out;
++ ext4_htree_safe_relock(lck);
+ ext4_clear_inode_flag(dir, EXT4_INODE_INDEX);
+ dx_fallback++;
+ ext4_mark_inode_dirty(handle, dir);
+@@ -2278,12 +2617,14 @@ out:
+ ext4_set_inode_state(inode, EXT4_STATE_NEWENTRY);
+ return retval;
+ }
++EXPORT_SYMBOL(__ext4_add_entry);
+
+ /*
+ * Returns 0 for success, or a negative error value
+ */
+ static int ext4_dx_add_entry(handle_t *handle, struct ext4_filename *fname,
+- struct inode *dir, struct inode *inode)
++ struct inode *dir, struct inode *inode,
++ struct htree_lock *lck)
+ {
+ struct dx_frame frames[EXT4_HTREE_LEVEL], *frame;
+ struct dx_entry *entries, *at;
+@@ -2295,7 +2636,7 @@ static int ext4_dx_add_entry(handle_t *h
+
+ again:
+ restart = 0;
+- frame = dx_probe(fname, dir, NULL, frames);
++ frame = dx_probe(fname, dir, NULL, frames, lck);
+ if (IS_ERR(frame))
+ return PTR_ERR(frame);
+ entries = frame->entries;
+@@ -2330,6 +2671,11 @@ again:
+ struct dx_node *node2;
+ struct buffer_head *bh2;
+
++ if (!ext4_htree_safe_locked(lck)) { /* retry with EX lock */
++ ext4_htree_safe_relock(lck);
++ restart = 1;
++ goto cleanup;
++ }
+ while (frame > frames) {
+ if (dx_get_count((frame - 1)->entries) <
+ dx_get_limit((frame - 1)->entries)) {
+@@ -2432,8 +2778,32 @@ again:
+ restart = 1;
+ goto journal_error;
+ }
++ } else if (!ext4_htree_dx_locked(lck)) {
++ struct ext4_dir_lock_data *ld = ext4_htree_lock_data(lck);
++
++ /* not well protected, require DX lock */
++ ext4_htree_dx_need_lock(lck);
++ at = frame > frames ? (frame - 1)->at : NULL;
++
++ /* NB: no risk of deadlock because it's just a try.
++ *
++ * NB: we check ld_count for twice, the first time before
++ * having DX lock, the second time after holding DX lock.
++ *
++ * NB: We never free blocks for directory so far, which
++ * means value returned by dx_get_count() should equal to
++ * ld->ld_count if nobody split any DE-block under @at,
++ * and ld->ld_at still points to valid dx_entry. */
++ if ((ld->ld_count != dx_get_count(entries)) ||
++ !ext4_htree_dx_lock_try(lck, at) ||
++ (ld->ld_count != dx_get_count(entries))) {
++ restart = 1;
++ goto cleanup;
++ }
++ /* OK, I've got DX lock and nothing changed */
++ frame->at = ld->ld_at;
+ }
+- de = do_split(handle, dir, &bh, frame, &fname->hinfo);
++ de = do_split(handle, dir, &bh, frames, frame, &fname->hinfo, lck);
+ if (IS_ERR(de)) {
+ err = PTR_ERR(de);
+ goto cleanup;
+@@ -2444,6 +2814,8 @@ again:
+ journal_error:
+ ext4_std_error(dir->i_sb, err); /* this is a no-op if err == 0 */
+ cleanup:
++ ext4_htree_dx_unlock(lck);
++ ext4_htree_de_unlock(lck);
+ brelse(bh);
+ dx_release(frames);
+ /* @restart is true means htree-path has been changed, we need to
+Index: linux-4.18.0-80.1.2.el8_0/fs/ext4/super.c
+===================================================================
+--- linux-4.18.0-80.1.2.el8_0.orig/fs/ext4/super.c
++++ linux-4.18.0-80.1.2.el8_0/fs/ext4/super.c
+@@ -1009,6 +1009,7 @@ static struct inode *ext4_alloc_inode(st
+
+ inode_set_iversion(&ei->vfs_inode, 1);
+ spin_lock_init(&ei->i_raw_lock);
++ sema_init(&ei->i_append_sem, 1);
+ INIT_LIST_HEAD(&ei->i_prealloc_list);
+ spin_lock_init(&ei->i_prealloc_lock);
+ ext4_es_init_tree(&ei->i_es_tree);
+Index: linux-4.18.0-80.1.2.el8_0/include/linux/htree_lock.h
+===================================================================
+--- /dev/null
++++ linux-4.18.0-80.1.2.el8_0/include/linux/htree_lock.h
+@@ -0,0 +1,187 @@
++/*
++ * include/linux/htree_lock.h
++ *
++ * Copyright (c) 2011, 2012, Intel Corporation.
++ *
++ * Author: Liang Zhen <liang@whamcloud.com>
++ */
++
++/*
++ * htree lock
++ *
++ * htree_lock is an advanced lock, it can support five lock modes (concept is
++ * taken from DLM) and it's a sleeping lock.
++ *
++ * most common use case is:
++ * - create a htree_lock_head for data
++ * - each thread (contender) creates it's own htree_lock
++ * - contender needs to call htree_lock(lock_node, mode) to protect data and
++ * call htree_unlock to release lock
++ *
++ * Also, there is advanced use-case which is more complex, user can have
++ * PW/PR lock on particular key, it's mostly used while user holding shared
++ * lock on the htree (CW, CR)
++ *
++ * htree_lock(lock_node, HTREE_LOCK_CR); lock the htree with CR
++ * htree_node_lock(lock_node, HTREE_LOCK_PR, key...); lock @key with PR
++ * ...
++ * htree_node_unlock(lock_node);; unlock the key
++ *
++ * Another tip is, we can have N-levels of this kind of keys, all we need to
++ * do is specifying N-levels while creating htree_lock_head, then we can
++ * lock/unlock a specific level by:
++ * htree_node_lock(lock_node, mode1, key1, level1...);
++ * do something;
++ * htree_node_lock(lock_node, mode1, key2, level2...);
++ * do something;
++ * htree_node_unlock(lock_node, level2);
++ * htree_node_unlock(lock_node, level1);
++ *
++ * NB: for multi-level, should be careful about locking order to avoid deadlock
++ */
++
++#ifndef _LINUX_HTREE_LOCK_H
++#define _LINUX_HTREE_LOCK_H
++
++#include <linux/list.h>
++#include <linux/spinlock.h>
++#include <linux/sched.h>
++
++/*
++ * Lock Modes
++ * more details can be found here:
++ * http://en.wikipedia.org/wiki/Distributed_lock_manager
++ */
++typedef enum {
++ HTREE_LOCK_EX = 0, /* exclusive lock: incompatible with all others */
++ HTREE_LOCK_PW, /* protected write: allows only CR users */
++ HTREE_LOCK_PR, /* protected read: allow PR, CR users */
++ HTREE_LOCK_CW, /* concurrent write: allow CR, CW users */
++ HTREE_LOCK_CR, /* concurrent read: allow all but EX users */
++ HTREE_LOCK_MAX, /* number of lock modes */
++} htree_lock_mode_t;
++
++#define HTREE_LOCK_NL HTREE_LOCK_MAX
++#define HTREE_LOCK_INVAL 0xdead10c
++
++enum {
++ HTREE_HBITS_MIN = 2,
++ HTREE_HBITS_DEF = 14,
++ HTREE_HBITS_MAX = 32,
++};
++
++enum {
++ HTREE_EVENT_DISABLE = (0),
++ HTREE_EVENT_RD = (1 << HTREE_LOCK_PR),
++ HTREE_EVENT_WR = (1 << HTREE_LOCK_PW),
++ HTREE_EVENT_RDWR = (HTREE_EVENT_RD | HTREE_EVENT_WR),
++};
++
++struct htree_lock;
++
++typedef void (*htree_event_cb_t)(void *target, void *event);
++
++struct htree_lock_child {
++ struct list_head lc_list; /* granted list */
++ htree_event_cb_t lc_callback; /* event callback */
++ unsigned lc_events; /* event types */
++};
++
++struct htree_lock_head {
++ unsigned long lh_lock; /* bits lock */
++ /* blocked lock list (htree_lock) */
++ struct list_head lh_blocked_list;
++ /* # key levels */
++ u16 lh_depth;
++ /* hash bits for key and limit number of locks */
++ u16 lh_hbits;
++ /* counters for blocked locks */
++ u16 lh_nblocked[HTREE_LOCK_MAX];
++ /* counters for granted locks */
++ u16 lh_ngranted[HTREE_LOCK_MAX];
++ /* private data */
++ void *lh_private;
++ /* array of children locks */
++ struct htree_lock_child lh_children[0];
++};
++
++/* htree_lock_node_t is child-lock for a specific key (ln_value) */
++struct htree_lock_node {
++ htree_lock_mode_t ln_mode;
++ /* major hash key */
++ u16 ln_major_key;
++ /* minor hash key */
++ u16 ln_minor_key;
++ struct list_head ln_major_list;
++ struct list_head ln_minor_list;
++ /* alive list, all locks (granted, blocked, listening) are on it */
++ struct list_head ln_alive_list;
++ /* blocked list */
++ struct list_head ln_blocked_list;
++ /* granted list */
++ struct list_head ln_granted_list;
++ void *ln_ev_target;
++};
++
++struct htree_lock {
++ struct task_struct *lk_task;
++ struct htree_lock_head *lk_head;
++ void *lk_private;
++ unsigned lk_depth;
++ htree_lock_mode_t lk_mode;
++ struct list_head lk_blocked_list;
++ struct htree_lock_node lk_nodes[0];
++};
++
++/* create a lock head, which stands for a resource */
++struct htree_lock_head *htree_lock_head_alloc(unsigned depth,
++ unsigned hbits, unsigned priv);
++/* free a lock head */
++void htree_lock_head_free(struct htree_lock_head *lhead);
++/* register event callback for child lock at level @depth */
++void htree_lock_event_attach(struct htree_lock_head *lhead, unsigned depth,
++ unsigned events, htree_event_cb_t callback);
++/* create a lock handle, which stands for a thread */
++struct htree_lock *htree_lock_alloc(unsigned depth, unsigned pbytes);
++/* free a lock handle */
++void htree_lock_free(struct htree_lock *lck);
++/* lock htree, when @wait is true, 0 is returned if the lock can't
++ * be granted immediately */
++int htree_lock_try(struct htree_lock *lck, struct htree_lock_head *lhead,
++ htree_lock_mode_t mode, int wait);
++/* unlock htree */
++void htree_unlock(struct htree_lock *lck);
++/* unlock and relock htree with @new_mode */
++int htree_change_lock_try(struct htree_lock *lck,
++ htree_lock_mode_t new_mode, int wait);
++void htree_change_mode(struct htree_lock *lck, htree_lock_mode_t mode);
++/* require child lock (key) of htree at level @dep, @event will be sent to all
++ * listeners on this @key while lock being granted */
++int htree_node_lock_try(struct htree_lock *lck, htree_lock_mode_t mode,
++ u32 key, unsigned dep, int wait, void *event);
++/* release child lock at level @dep, this lock will listen on it's key
++ * if @event isn't NULL, event_cb will be called against @lck while granting
++ * any other lock at level @dep with the same key */
++void htree_node_unlock(struct htree_lock *lck, unsigned dep, void *event);
++/* stop listening on child lock at level @dep */
++void htree_node_stop_listen(struct htree_lock *lck, unsigned dep);
++/* for debug */
++void htree_lock_stat_print(int depth);
++void htree_lock_stat_reset(void);
++
++#define htree_lock(lck, lh, mode) htree_lock_try(lck, lh, mode, 1)
++#define htree_change_lock(lck, mode) htree_change_lock_try(lck, mode, 1)
++
++#define htree_lock_mode(lck) ((lck)->lk_mode)
++
++#define htree_node_lock(lck, mode, key, dep) \
++ htree_node_lock_try(lck, mode, key, dep, 1, NULL)
++/* this is only safe in thread context of lock owner */
++#define htree_node_is_granted(lck, dep) \
++ ((lck)->lk_nodes[dep].ln_mode != HTREE_LOCK_INVAL && \
++ (lck)->lk_nodes[dep].ln_mode != HTREE_LOCK_NL)
++/* this is only safe in thread context of lock owner */
++#define htree_node_is_listening(lck, dep) \
++ ((lck)->lk_nodes[dep].ln_mode == HTREE_LOCK_NL)
++
++#endif
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