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fs: dcache reduce dput locking 

It is possible to run dput without taking data structure locks up-front. In
many cases where we don't kill the dentry anyway, these locks are not required.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
This commit is contained in:
Nick Piggin 2011-01-07 17:49:40 +11:00
parent 58db63d086
commit 61f3dee4af
1 changed files with 23 additions and 29 deletions
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52
fs/dcache.c
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@ -323,35 +323,16 @@ repeat:
if (dentry->d_count == 1)
might_sleep();
spin_lock(&dentry->d_lock);
if (IS_ROOT(dentry))
parent = NULL;
else
parent = dentry->d_parent;
if (dentry->d_count == 1) {
if (!spin_trylock(&dcache_inode_lock)) {
drop2:
spin_unlock(&dentry->d_lock);
goto repeat;
}
if (parent && !spin_trylock(&parent->d_lock)) {
spin_unlock(&dcache_inode_lock);
goto drop2;
}
}
dentry->d_count--;
if (dentry->d_count) {
BUG_ON(!dentry->d_count);
if (dentry->d_count > 1) {
dentry->d_count--;
spin_unlock(&dentry->d_lock);
if (parent)
spin_unlock(&parent->d_lock);
return;
}
/*
* AV: ->d_delete() is _NOT_ allowed to block now.
*/
if (dentry->d_op && dentry->d_op->d_delete) {
if (dentry->d_op->d_delete(dentry))
goto unhash_it;
goto kill_it;
}
/* Unreachable? Get rid of it */
@ -362,17 +343,30 @@ drop2:
dentry->d_flags |= DCACHE_REFERENCED;
dentry_lru_add(dentry);
spin_unlock(&dentry->d_lock);
if (parent)
spin_unlock(&parent->d_lock);
spin_unlock(&dcache_inode_lock);
dentry->d_count--;
spin_unlock(&dentry->d_lock);
return;
unhash_it:
__d_drop(dentry);
kill_it:
if (!spin_trylock(&dcache_inode_lock)) {
relock:
spin_unlock(&dentry->d_lock);
cpu_relax();
goto repeat;
}
if (IS_ROOT(dentry))
parent = NULL;
else
parent = dentry->d_parent;
if (parent && !spin_trylock(&parent->d_lock)) {
spin_unlock(&dcache_inode_lock);
goto relock;
}
dentry->d_count--;
/* if dentry was on the d_lru list delete it from there */
dentry_lru_del(dentry);
/* if it was on the hash (d_delete case), then remove it */
__d_drop(dentry);
dentry = d_kill(dentry, parent);
if (dentry)
goto repeat;