b=24201 add procfs tunable to enable/disable lockless direct I/O

llite.lustre-*.lockless_direct_io=0 will disable default semantics
of direct I/O that forces it to be lockless. lockless_direct_io value,
however, will be ignored if per-file LL_FILE_LOCKED_DIRECTIO bit
is set.

i=Johann Lombardi

diff --git a/lustre/llite/file.c b/lustre/llite/file.c
index 882bfaa..6acf7f5 100644 (file)
--- a/lustre/llite/file.c
+++ b/lustre/llite/file.c
@@ -1143,9 +1143,16 @@ static int ll_is_file_contended(struct file *file)
         if (fd && (fd->fd_flags & LL_FILE_IGNORE_LOCK))
                 RETURN(0);
 
-        /* server-side locking for dio unless LL_FILE_LOCKED_DIRECTIO */
+        /* The semantics here is a bit complicated due to compatibility.
+         * The user may be aware of per-file LL_FILE_LOCKED_DIRECTIO,
+         * but not of per-client lockless_direct_io, so the file bit takes
+         * precedence if it is set. If the file bit is not set, we use
+         * lockless I/O unless per-client lockless_direct_io is set to zero.
+         */
+        CLASSERT(SBI_DEFAULT_LOCKLESS_DIRECT_IO == 1);
         if ((file->f_flags & O_DIRECT) &&
-            !(fd && (fd->fd_flags & LL_FILE_LOCKED_DIRECTIO)))
+            !(fd && (fd->fd_flags & LL_FILE_LOCKED_DIRECTIO)) &&
+            sbi->ll_lockless_direct_io)
                 RETURN(1);
 
         /* server-side locking for cached I/O with LL_FILE_LOCKLESS_IO */

diff --git a/lustre/llite/llite_internal.h b/lustre/llite/llite_internal.h
index 70ab767..b35f799 100644 (file)
--- a/lustre/llite/llite_internal.h
+++ b/lustre/llite/llite_internal.h
@@ -311,6 +311,7 @@ enum stats_track_type {
 #define SBI_DEFAULT_LOCKLESS_TRUNCATE_ENABLE 0 /* see bug 23175 */
 /* default value for ll_direct_io_default */
 #define SBI_DEFAULT_DIRECT_IO_DEFAULT 0
+#define SBI_DEFAULT_LOCKLESS_DIRECT_IO 1
 
 /* percpu data structure for lustre lru page list */
 struct ll_pglist_data {
@@ -370,6 +371,7 @@ struct ll_sb_info {
 
         unsigned                  ll_contention_time; /* seconds */
         unsigned                  ll_lockless_truncate_enable; /* true/false */
+        unsigned                  ll_lockless_direct_io; /* true/false */
         unsigned                  ll_direct_io_default; /* true/false */
 
         struct ll_ra_info         ll_ra_info;

diff --git a/lustre/llite/llite_lib.c b/lustre/llite/llite_lib.c
index a0bd6ad..4c60593 100644 (file)
--- a/lustre/llite/llite_lib.c
+++ b/lustre/llite/llite_lib.c
@@ -176,6 +176,7 @@ static struct ll_sb_info *ll_init_sbi(void)
                                            SBI_DEFAULT_READAHEAD_WHOLE_MAX;
         sbi->ll_contention_time = SBI_DEFAULT_CONTENTION_SECONDS;
         sbi->ll_lockless_truncate_enable = SBI_DEFAULT_LOCKLESS_TRUNCATE_ENABLE;
+        sbi->ll_lockless_direct_io = SBI_DEFAULT_LOCKLESS_DIRECT_IO;
         sbi->ll_direct_io_default = SBI_DEFAULT_DIRECT_IO_DEFAULT;
         INIT_LIST_HEAD(&sbi->ll_conn_chain);
         INIT_LIST_HEAD(&sbi->ll_orphan_dentry_list);

diff --git a/lustre/llite/lproc_llite.c b/lustre/llite/lproc_llite.c
index 15b514a..c6f280b 100644 (file)
--- a/lustre/llite/lproc_llite.c
+++ b/lustre/llite/lproc_llite.c
@@ -597,6 +597,27 @@ static int ll_wr_direct_io_default(struct file *file, const char *buffer,
                 ?: count;
 }
 
+static int ll_rd_lockless_direct_io(char *page, char **start, off_t off,
+                                    int count, int *eof, void *data)
+{
+        struct super_block *sb = data;
+
+        *eof = 1;
+        return snprintf(page, count, "%u\n",
+                        ll_s2sbi(sb)->ll_lockless_direct_io);
+}
+
+static int ll_wr_lockless_direct_io(struct file *file, const char *buffer,
+                                    unsigned long count, void *data)
+{
+        struct super_block *sb = data;
+        struct ll_sb_info *sbi = ll_s2sbi(sb);
+
+        return lprocfs_write_helper(buffer, count,
+                                    &sbi->ll_lockless_direct_io)
+                ?: count;
+}
+
 static int ll_rd_statahead_max(char *page, char **start, off_t off,
                                int count, int *eof, void *data)
 {
@@ -704,6 +725,8 @@ static struct lprocfs_vars lprocfs_llite_obd_vars[] = {
                                 ll_wr_contention_time, 0},
         { "lockless_truncate", ll_rd_lockless_truncate,
                                ll_wr_lockless_truncate, 0},
+        { "lockless_direct_io", ll_rd_lockless_direct_io,
+                               ll_wr_lockless_direct_io, 0},
         { "direct_io_default", ll_rd_direct_io_default,
                                ll_wr_direct_io_default, 0},
         { "statahead_max",      ll_rd_statahead_max, ll_wr_statahead_max, 0 },