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-rw-r--r--fs/fs-writeback.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index f45bf876579f..3c974442bdf0 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -2114,6 +2114,15 @@ out_unlock_inode:
}
EXPORT_SYMBOL(__mark_inode_dirty);
+/*
+ * The @s_sync_lock is used to serialise concurrent sync operations
+ * to avoid lock contention problems with concurrent wait_sb_inodes() calls.
+ * Concurrent callers will block on the s_sync_lock rather than doing contending
+ * walks. The queueing maintains sync(2) required behaviour as all the IO that
+ * has been issued up to the time this function is enter is guaranteed to be
+ * completed by the time we have gained the lock and waited for all IO that is
+ * in progress regardless of the order callers are granted the lock.
+ */
static void wait_sb_inodes(struct super_block *sb)
{
struct inode *inode, *old_inode = NULL;
@@ -2124,6 +2133,7 @@ static void wait_sb_inodes(struct super_block *sb)
*/
WARN_ON(!rwsem_is_locked(&sb->s_umount));
+ mutex_lock(&sb->s_sync_lock);
spin_lock(&sb->s_inode_list_lock);
/*
@@ -2165,6 +2175,7 @@ static void wait_sb_inodes(struct super_block *sb)
}
spin_unlock(&sb->s_inode_list_lock);
iput(old_inode);
+ mutex_unlock(&sb->s_sync_lock);
}
static void __writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr,