From 98474236f72e5a8b89c14cd7c74f0bb77a4b1a99 Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Wed, 28 Aug 2013 18:24:59 -0700 Subject: vfs: make the dentry cache use the lockref infrastructure This just replaces the dentry count/lock combination with the lockref structure that contains both a count and a spinlock, and does the mechanical conversion to use the lockref infrastructure. There are no semantic changes here, it's purely syntactic. The reference lockref implementation uses the spinlock exactly the same way that the old dcache code did, and the bulk of this patch is just expanding the internal "d_count" use in the dcache code to use "d_lockref.count" instead. This is purely preparation for the real change to make the reference count updates be lockless during the 3.12 merge window. [ As with the previous commit, this is a rewritten version of a concept originally from Waiman, so credit goes to him, blame for any errors goes to me. Waiman's patch had some semantic differences for taking advantage of the lockless update in dget_parent(), while this patch is intentionally a pure search-and-replace change with no semantic changes. - Linus ] Signed-off-by: Waiman Long Signed-off-by: Linus Torvalds --- fs/dcache.c | 57 +++++++++++++++++++++++---------------------------------- 1 file changed, 23 insertions(+), 34 deletions(-) (limited to 'fs/dcache.c') diff --git a/fs/dcache.c b/fs/dcache.c index 83cfb834db03..b949af850cd6 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -229,7 +229,7 @@ static void __d_free(struct rcu_head *head) */ static void d_free(struct dentry *dentry) { - BUG_ON(dentry->d_count); + BUG_ON(dentry->d_lockref.count); this_cpu_dec(nr_dentry); if (dentry->d_op && dentry->d_op->d_release) dentry->d_op->d_release(dentry); @@ -467,7 +467,7 @@ relock: } if (ref) - dentry->d_count--; + dentry->d_lockref.count--; /* * inform the fs via d_prune that this dentry is about to be * unhashed and destroyed. @@ -513,15 +513,10 @@ void dput(struct dentry *dentry) return; repeat: - if (dentry->d_count == 1) + if (dentry->d_lockref.count == 1) might_sleep(); - spin_lock(&dentry->d_lock); - BUG_ON(!dentry->d_count); - if (dentry->d_count > 1) { - dentry->d_count--; - spin_unlock(&dentry->d_lock); + if (lockref_put_or_lock(&dentry->d_lockref)) return; - } if (dentry->d_flags & DCACHE_OP_DELETE) { if (dentry->d_op->d_delete(dentry)) @@ -535,7 +530,7 @@ repeat: dentry->d_flags |= DCACHE_REFERENCED; dentry_lru_add(dentry); - dentry->d_count--; + dentry->d_lockref.count--; spin_unlock(&dentry->d_lock); return; @@ -590,7 +585,7 @@ int d_invalidate(struct dentry * dentry) * We also need to leave mountpoints alone, * directory or not. */ - if (dentry->d_count > 1 && dentry->d_inode) { + if (dentry->d_lockref.count > 1 && dentry->d_inode) { if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) { spin_unlock(&dentry->d_lock); return -EBUSY; @@ -606,14 +601,12 @@ EXPORT_SYMBOL(d_invalidate); /* This must be called with d_lock held */ static inline void __dget_dlock(struct dentry *dentry) { - dentry->d_count++; + dentry->d_lockref.count++; } static inline void __dget(struct dentry *dentry) { - spin_lock(&dentry->d_lock); - __dget_dlock(dentry); - spin_unlock(&dentry->d_lock); + lockref_get(&dentry->d_lockref); } struct dentry *dget_parent(struct dentry *dentry) @@ -634,8 +627,8 @@ repeat: goto repeat; } rcu_read_unlock(); - BUG_ON(!ret->d_count); - ret->d_count++; + BUG_ON(!ret->d_lockref.count); + ret->d_lockref.count++; spin_unlock(&ret->d_lock); return ret; } @@ -718,7 +711,7 @@ restart: spin_lock(&inode->i_lock); hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) { spin_lock(&dentry->d_lock); - if (!dentry->d_count) { + if (!dentry->d_lockref.count) { __dget_dlock(dentry); __d_drop(dentry); spin_unlock(&dentry->d_lock); @@ -763,12 +756,8 @@ static void try_prune_one_dentry(struct dentry *dentry) /* Prune ancestors. */ dentry = parent; while (dentry) { - spin_lock(&dentry->d_lock); - if (dentry->d_count > 1) { - dentry->d_count--; - spin_unlock(&dentry->d_lock); + if (lockref_put_or_lock(&dentry->d_lockref)) return; - } dentry = dentry_kill(dentry, 1); } } @@ -793,7 +782,7 @@ static void shrink_dentry_list(struct list_head *list) * the LRU because of laziness during lookup. Do not free * it - just keep it off the LRU list. */ - if (dentry->d_count) { + if (dentry->d_lockref.count) { dentry_lru_del(dentry); spin_unlock(&dentry->d_lock); continue; @@ -913,7 +902,7 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry) dentry_lru_del(dentry); __d_shrink(dentry); - if (dentry->d_count != 0) { + if (dentry->d_lockref.count != 0) { printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%s}" " still in use (%d)" @@ -922,7 +911,7 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry) dentry->d_inode ? dentry->d_inode->i_ino : 0UL, dentry->d_name.name, - dentry->d_count, + dentry->d_lockref.count, dentry->d_sb->s_type->name, dentry->d_sb->s_id); BUG(); @@ -933,7 +922,7 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry) list_del(&dentry->d_u.d_child); } else { parent = dentry->d_parent; - parent->d_count--; + parent->d_lockref.count--; list_del(&dentry->d_u.d_child); } @@ -981,7 +970,7 @@ void shrink_dcache_for_umount(struct super_block *sb) dentry = sb->s_root; sb->s_root = NULL; - dentry->d_count--; + dentry->d_lockref.count--; shrink_dcache_for_umount_subtree(dentry); while (!hlist_bl_empty(&sb->s_anon)) { @@ -1147,7 +1136,7 @@ resume: * loop in shrink_dcache_parent() might not make any progress * and loop forever. */ - if (dentry->d_count) { + if (dentry->d_lockref.count) { dentry_lru_del(dentry); } else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) { dentry_lru_move_list(dentry, dispose); @@ -1269,7 +1258,7 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name) smp_wmb(); dentry->d_name.name = dname; - dentry->d_count = 1; + dentry->d_lockref.count = 1; dentry->d_flags = 0; spin_lock_init(&dentry->d_lock); seqcount_init(&dentry->d_seq); @@ -1970,7 +1959,7 @@ struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name) goto next; } - dentry->d_count++; + dentry->d_lockref.count++; found = dentry; spin_unlock(&dentry->d_lock); break; @@ -2069,7 +2058,7 @@ again: spin_lock(&dentry->d_lock); inode = dentry->d_inode; isdir = S_ISDIR(inode->i_mode); - if (dentry->d_count == 1) { + if (dentry->d_lockref.count == 1) { if (!spin_trylock(&inode->i_lock)) { spin_unlock(&dentry->d_lock); cpu_relax(); @@ -2948,7 +2937,7 @@ resume: } if (!(dentry->d_flags & DCACHE_GENOCIDE)) { dentry->d_flags |= DCACHE_GENOCIDE; - dentry->d_count--; + dentry->d_lockref.count--; } spin_unlock(&dentry->d_lock); } @@ -2956,7 +2945,7 @@ resume: struct dentry *child = this_parent; if (!(this_parent->d_flags & DCACHE_GENOCIDE)) { this_parent->d_flags |= DCACHE_GENOCIDE; - this_parent->d_count--; + this_parent->d_lockref.count--; } this_parent = try_to_ascend(this_parent, locked, seq); if (!this_parent) -- cgit v1.2.3-55-g7522