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Subject[PATCH 23/46] 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@kernel.dk>
---
fs/dcache.c | 24 ++++++++++++------------
1 files changed, 12 insertions(+), 12 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index 3e4f7c1..6fe387d 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1794,10 +1794,15 @@ 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);
@@ -1808,7 +1813,6 @@ void d_delete(struct dentry * dentry)
__d_drop(dentry);

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

fsnotify_nameremove(dentry, isdir);
}
@@ -2106,14 +2110,15 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)

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;

@@ -2145,10 +2150,9 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
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:
spin_lock(&dcache_hash_lock);
@@ -2164,10 +2168,6 @@ out_nolock:

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

--
1.7.1


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