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Subject[patch 20/52] fs: dcache reduce dcache_inode_lock
dcache_inode_lock can be avoided in d_delete() and d_materialise_unique()
in cases where it is not required.

Signed-off-by: Nick Piggin <npiggin@suse.de>
---
fs/dcache.c | 23 +++++++++++------------
1 file changed, 11 insertions(+), 12 deletions(-)
Index: linux-2.6/fs/dcache.c
===================================================================
--- linux-2.6.orig/fs/dcache.c
+++ linux-2.6/fs/dcache.c
@@ -1789,10 +1789,15 @@ void d_delete(struct dentry * dentry)
/*
* Are we the only user?
*/
- spin_lock(&dcache_inode_lock);
+again:
spin_lock(&dentry->d_lock);
isdir = S_ISDIR(dentry->d_inode->i_mode);
if (dentry->d_count == 1) {
+ if (!spin_trylock(&dcache_inode_lock)) {
+ spin_unlock(&dentry->d_lock);
+ cpu_relax();
+ goto again;
+ }
dentry->d_flags &= ~DCACHE_CANT_MOUNT;
dentry_iput(dentry);
fsnotify_nameremove(dentry, isdir);
@@ -1803,7 +1808,6 @@ void d_delete(struct dentry * dentry)
__d_drop(dentry);

spin_unlock(&dentry->d_lock);
- spin_unlock(&dcache_inode_lock);

fsnotify_nameremove(dentry, isdir);
}
@@ -2116,14 +2120,15 @@ struct dentry *d_materialise_unique(stru

BUG_ON(!d_unhashed(dentry));

- spin_lock(&dcache_inode_lock);
-
if (!inode) {
actual = dentry;
__d_instantiate(dentry, NULL);
- goto found_lock;
+ d_rehash(actual);
+ goto out_nolock;
}

+ spin_lock(&dcache_inode_lock);
+
if (S_ISDIR(inode->i_mode)) {
struct dentry *alias;

@@ -2150,10 +2155,9 @@ struct dentry *d_materialise_unique(stru
actual = __d_instantiate_unique(dentry, inode);
if (!actual)
actual = dentry;
- else if (unlikely(!d_unhashed(actual)))
- goto shouldnt_be_hashed;
+ else
+ BUG_ON(!d_unhashed(actual));

-found_lock:
spin_lock(&actual->d_lock);
found:
_d_rehash(actual);
@@ -2167,10 +2171,6 @@ out_nolock:

iput(inode);
return actual;
-
-shouldnt_be_hashed:
- spin_unlock(&dcache_inode_lock);
- BUG();
}
EXPORT_SYMBOL_GPL(d_materialise_unique);




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