--- /dev/null
+ext4: parallel directory locking for htree
+
+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 ext4 directory. Parallel Directory Operations will remove this
+bottleneck by introducing a parallel locking mechanism within one
+ext4 directory. This work will enable multiple application threads
+to simultaneously lookup, create and unlink in parallel.
+
+This patch contains the parallel htree locking for ext4 directories.
+The idea is simple, like how pdirop is implement at LDLM level.
+
+ - implement advanced lock with multiple modes (CR, PR, CW, PW, EX)
+ (see https://en.wikipedia.org/wiki/Distributed_lock_manager for details)
+ - it's just a resource lock that resides in above the ext4 directory, which
+ replaces current monolithic semaphore locking the whole directory
+ - protect sub-resources by locking N hash keys when holding CR & CW
+ * for Concurrent Read (CR), sub locking is Protected Read (PR)
+ * for Concurrent Write (CW), sub locking is Protected Write (PW)
+ - for !is_dx(dir):
+ * change operations always hold Exclusive (EX) lock on
+ dir, lookup & readdir hold PR lock on dir
+ - for is_dx(dir):
+ * change operations take CW lock, then take two sub-locks:
+ + name-hash as the first key, + block number as the second key
+ * lookup take CR lock, then take two sub-locks:
+ + name-hash as the first key, + block number as the second key
+ * readdir take PR lock:
+ + for Lustre it's not necessary to take PR lock, but we already have
+ PR lock in ldlm level, and this is needed for non-Lustre usage
+ - if we need to split any blocks (name entries block or indexing block)
+ while holding CW lock, we drop CW lock and take EX lock and retry.
+ - disable pdirops by always EX lock on change and PR lock on lookup/readdir.
+
+Lustre-bug-id: LU-50" target="_blank">https://jira.whamcloud.com/browse/LU-50
+Lustre-change: http://review.whamcloud.com/375
+Signed-off-by: Liang Zhen <liang@whamcloud.com>
+
+
+Index: linux-3.10.0-229.1.2.fc21.x86_64/include/linux/htree_lock.h
+===================================================================
+--- /dev/null
++++ linux-3.10.0-229.1.2.fc21.x86_64/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
+Index: linux-3.10.0-229.1.2.fc21.x86_64/fs/ext4/htree_lock.c
+===================================================================
+--- /dev/null
++++ linux-3.10.0-229.1.2.fc21.x86_64/fs/ext4/htree_lock.c
+@@ -0,0 +1,895 @@
++/*
++ * 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;
++ /* 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);
++
++retry:
++ set_current_state(TASK_UNINTERRUPTIBLE);
++ 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 */
++ htree_spin_lock(newlk->lk_head, dep);
++ /* Need to check lock really granted, thread maybe awaken wrongly */
++ if (list_empty(&newln->ln_granted_list) && htree_key_list_empty(newln))
++ goto retry;
++ if (event && !htree_key_event_ignore(child, newln))
++ 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)
++ hbits = HTREE_HBITS_MIN;
++ else if (hbits > HTREE_HBITS_MAX)
++ hbits = HTREE_HBITS_MAX;
++
++ lhead->lh_hbits = hbits;
++ 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);
git://git.whamcloud.com / fs / lustre-release.git / blobdiff