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Commit 19156840 authored by Dave Chinner's avatar Dave Chinner Committed by Al Viro
Browse files

dentry: move to per-sb LRU locks 



With the dentry LRUs being per-sb structures, there is no real need for
a global dentry_lru_lock. The locking can be made more fine-grained by
moving to a per-sb LRU lock, isolating the LRU operations of different
filesytsems completely from each other. The need for this is independent
of any performance consideration that may arise: in the interest of
abstracting the lru operations away, it is mandatory that each lru works
around its own lock instead of a global lock for all of them.

[glommer@openvz.org: updated changelog ]
Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
Signed-off-by: default avatarGlauber Costa <glommer@openvz.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Acked-by: default avatarMel Gorman <mgorman@suse.de>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Carlos Maiolino <cmaiolino@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Rientjes <rientjes@google.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: J. Bruce Fields <bfields@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Kent Overstreet <koverstreet@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 62d36c77

fs/dcache.c

+16 −17
Original line number Diff line number Diff line
@@ -48,7 +48,7 @@ 
 *   - the dcache hash table

 * s_anon bl list spinlock protects:

 *   - the s_anon list (see __d_drop)

 * dcache_lru_lock protects:

 * dentry->d_sb->s_dentry_lru_lock protects:

 *   - the dcache lru lists and counters

 * d_lock protects:

 *   - d_flags
@@ -63,7 +63,7 @@ 
 * Ordering:

 * dentry->d_inode->i_lock

 *   dentry->d_lock

 *     dcache_lru_lock

 *     dentry->d_sb->s_dentry_lru_lock

 *     dcache_hash_bucket lock

 *     s_anon lock

 *
@@ -81,7 +81,6 @@ 
int sysctl_vfs_cache_pressure __read_mostly = 100;

EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);



static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);

__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);



EXPORT_SYMBOL(rename_lock);
@@ -362,12 +361,12 @@ static void dentry_unlink_inode(struct dentry * dentry) 
static void dentry_lru_add(struct dentry *dentry)

{

	if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST))) {

		spin_lock(&dcache_lru_lock);

		spin_lock(&dentry->d_sb->s_dentry_lru_lock);

		dentry->d_flags |= DCACHE_LRU_LIST;

		list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);

		dentry->d_sb->s_nr_dentry_unused++;

		this_cpu_inc(nr_dentry_unused);

		spin_unlock(&dcache_lru_lock);

		spin_unlock(&dentry->d_sb->s_dentry_lru_lock);

	}

}
@@ -385,15 +384,15 @@ static void __dentry_lru_del(struct dentry *dentry) 
static void dentry_lru_del(struct dentry *dentry)

{

	if (!list_empty(&dentry->d_lru)) {

		spin_lock(&dcache_lru_lock);

		spin_lock(&dentry->d_sb->s_dentry_lru_lock);

		__dentry_lru_del(dentry);

		spin_unlock(&dcache_lru_lock);

		spin_unlock(&dentry->d_sb->s_dentry_lru_lock);

	}

}



static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list)

{

	spin_lock(&dcache_lru_lock);

	spin_lock(&dentry->d_sb->s_dentry_lru_lock);

	if (list_empty(&dentry->d_lru)) {

		dentry->d_flags |= DCACHE_LRU_LIST;

		list_add_tail(&dentry->d_lru, list);
@@ -402,7 +401,7 @@ static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list) 
	} else {

		list_move_tail(&dentry->d_lru, list);

	}

	spin_unlock(&dcache_lru_lock);

	spin_unlock(&dentry->d_sb->s_dentry_lru_lock);

}



/**
@@ -895,14 +894,14 @@ void prune_dcache_sb(struct super_block *sb, int count) 
	LIST_HEAD(tmp);



relock:

	spin_lock(&dcache_lru_lock);

	spin_lock(&sb->s_dentry_lru_lock);

	while (!list_empty(&sb->s_dentry_lru)) {

		dentry = list_entry(sb->s_dentry_lru.prev,

				struct dentry, d_lru);

		BUG_ON(dentry->d_sb != sb);



		if (!spin_trylock(&dentry->d_lock)) {

			spin_unlock(&dcache_lru_lock);

			spin_unlock(&sb->s_dentry_lru_lock);

			cpu_relax();

			goto relock;

		}
@@ -918,11 +917,11 @@ relock: 
			if (!--count)

				break;

		}

		cond_resched_lock(&dcache_lru_lock);

		cond_resched_lock(&sb->s_dentry_lru_lock);

	}

	if (!list_empty(&referenced))

		list_splice(&referenced, &sb->s_dentry_lru);

	spin_unlock(&dcache_lru_lock);

	spin_unlock(&sb->s_dentry_lru_lock);



	shrink_dentry_list(&tmp);

}
@@ -938,14 +937,14 @@ void shrink_dcache_sb(struct super_block *sb) 
{

	LIST_HEAD(tmp);



	spin_lock(&dcache_lru_lock);

	spin_lock(&sb->s_dentry_lru_lock);

	while (!list_empty(&sb->s_dentry_lru)) {

		list_splice_init(&sb->s_dentry_lru, &tmp);

		spin_unlock(&dcache_lru_lock);

		spin_unlock(&sb->s_dentry_lru_lock);

		shrink_dentry_list(&tmp);

		spin_lock(&dcache_lru_lock);

		spin_lock(&sb->s_dentry_lru_lock);

	}

	spin_unlock(&dcache_lru_lock);

	spin_unlock(&sb->s_dentry_lru_lock);

}

EXPORT_SYMBOL(shrink_dcache_sb);

fs/super.c

+1 −0
Original line number Diff line number Diff line
@@ -176,6 +176,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags) 
		INIT_HLIST_BL_HEAD(&s->s_anon);

		INIT_LIST_HEAD(&s->s_inodes);

		INIT_LIST_HEAD(&s->s_dentry_lru);

		spin_lock_init(&s->s_dentry_lru_lock);

		INIT_LIST_HEAD(&s->s_inode_lru);

		spin_lock_init(&s->s_inode_lru_lock);

		INIT_LIST_HEAD(&s->s_mounts);

include/linux/fs.h

+3 −1
Original line number Diff line number Diff line
@@ -1269,7 +1269,9 @@ struct super_block { 
	struct list_head	s_files;

#endif

	struct list_head	s_mounts;	/* list of mounts; _not_ for fs use */

	/* s_dentry_lru, s_nr_dentry_unused protected by dcache.c lru locks */



	/* s_dentry_lru_lock protects s_dentry_lru and s_nr_dentry_unused */

	spinlock_t		s_dentry_lru_lock ____cacheline_aligned_in_smp;

	struct list_head	s_dentry_lru;	/* unused dentry lru */

	long			s_nr_dentry_unused;	/* # of dentry on lru */