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fs: dcache scale subdirs

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Protect d_subdirs and d_child with d_lock, except in filesystems that aren't
using dcache_lock for these anyway (eg. using i_mutex).

Note: if we change the locking rule in future so that ->d_child protection is
provided only with ->d_parent->d_lock, it may allow us to reduce some locking.
But it would be an exception to an otherwise regular locking scheme, so we'd
have to see some good results. Probably not worthwhile.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
This commit is contained in:
Nick Piggin
2011-01-07 17:49:34 +11:00
parent da5029563a
commit 2fd6b7f507
16 changed files with 338 additions and 159 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/cgroup.c
+17 -2
View File
@@ -877,23 +877,31 @@ static void cgroup_clear_directory(struct dentry *dentry)
BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
node = dentry->d_subdirs.next;
while (node != &dentry->d_subdirs) {
struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
list_del_init(node);
if (d->d_inode) {
/* This should never be called on a cgroup
* directory with child cgroups */
BUG_ON(d->d_inode->i_mode & S_IFDIR);
d = dget_locked(d);
dget_locked_dlock(d);
spin_unlock(&d->d_lock);
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
d_delete(d);
simple_unlink(dentry->d_inode, d);
dput(d);
spin_lock(&dcache_lock);
}
spin_lock(&dentry->d_lock);
} else
spin_unlock(&d->d_lock);
node = dentry->d_subdirs.next;
}
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
}
@@ -902,10 +910,17 @@ static void cgroup_clear_directory(struct dentry *dentry)
*/
static void cgroup_d_remove_dir(struct dentry *dentry)
{
struct dentry *parent;
cgroup_clear_directory(dentry);
spin_lock(&dcache_lock);
parent = dentry->d_parent;
spin_lock(&parent->d_lock);
spin_lock(&dentry->d_lock);
list_del_init(&dentry->d_u.d_child);
spin_unlock(&dentry->d_lock);
spin_unlock(&parent->d_lock);
spin_unlock(&dcache_lock);
remove_dir(dentry);
}