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fs: consolidate dentry kill sequence

Browse source 
The tricky locking for disposing of a dentry is duplicated 3 times in the
dcache (dput, pruning a dentry from the LRU, and pruning its ancestors).
Consolidate them all into a single function dentry_kill.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
This commit is contained in:
Nick Piggin 2011-01-07 17:49:48 +11:00
parent ec33679d78
commit 77812a1ef1
1 changed files with 61 additions and 74 deletions
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135
fs/dcache.c
View file

@ -284,6 +284,40 @@ void d_drop(struct dentry *dentry)
}
EXPORT_SYMBOL(d_drop);
/*
* Finish off a dentry we've decided to kill.
* dentry->d_lock must be held, returns with it unlocked.
* If ref is non-zero, then decrement the refcount too.
* Returns dentry requiring refcount drop, or NULL if we're done.
*/
static inline struct dentry *dentry_kill(struct dentry *dentry, int ref)
__releases(dentry->d_lock)
{
struct dentry *parent;
if (!spin_trylock(&dcache_inode_lock)) {
relock:
spin_unlock(&dentry->d_lock);
cpu_relax();
return dentry; /* try again with same dentry */
}
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;
}
if (ref)
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 then remove it */
__d_drop(dentry);
return d_kill(dentry, parent);
}
/*
* This is dput
*
@ -309,13 +343,9 @@ EXPORT_SYMBOL(d_drop);
* call the dentry unlink method as well as removing it from the queues and
* releasing its resources. If the parent dentries were scheduled for release
* they too may now get deleted.
*
* no dcache lock, please.
*/
void dput(struct dentry *dentry)
{
struct dentry *parent;
if (!dentry)
return;
@ -348,26 +378,7 @@ repeat:
return;
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);
dentry = dentry_kill(dentry, 1);
if (dentry)
goto repeat;
}
@ -563,51 +574,43 @@ restart:
EXPORT_SYMBOL(d_prune_aliases);
/*
* Throw away a dentry - free the inode, dput the parent. This requires that
* the LRU list has already been removed.
* Try to throw away a dentry - free the inode, dput the parent.
* Requires dentry->d_lock is held, and dentry->d_count == 0.
* Releases dentry->d_lock.
*
* Try to prune ancestors as well. This is necessary to prevent
* quadratic behavior of shrink_dcache_parent(), but is also expected
* to be beneficial in reducing dentry cache fragmentation.
* This may fail if locks cannot be acquired no problem, just try again.
*/
static void prune_one_dentry(struct dentry *dentry, struct dentry *parent)
static void try_prune_one_dentry(struct dentry *dentry)
__releases(dentry->d_lock)
__releases(parent->d_lock)
__releases(dcache_inode_lock)
{
__d_drop(dentry);
dentry = d_kill(dentry, parent);
struct dentry *parent;
parent = dentry_kill(dentry, 0);
/*
* Prune ancestors.
* If dentry_kill returns NULL, we have nothing more to do.
* if it returns the same dentry, trylocks failed. In either
* case, just loop again.
*
* Otherwise, we need to prune ancestors too. This is necessary
* to prevent quadratic behavior of shrink_dcache_parent(), but
* is also expected to be beneficial in reducing dentry cache
* fragmentation.
*/
if (!parent)
return;
if (parent == dentry)
return;
/* Prune ancestors. */
dentry = parent;
while (dentry) {
relock:
spin_lock(&dentry->d_lock);
if (dentry->d_count > 1) {
dentry->d_count--;
spin_unlock(&dentry->d_lock);
return;
}
if (!spin_trylock(&dcache_inode_lock)) {
relock2:
spin_unlock(&dentry->d_lock);
cpu_relax();
goto relock;
}
if (IS_ROOT(dentry))
parent = NULL;
else
parent = dentry->d_parent;
if (parent && !spin_trylock(&parent->d_lock)) {
spin_unlock(&dcache_inode_lock);
goto relock2;
}
dentry->d_count--;
dentry_lru_del(dentry);
__d_drop(dentry);
dentry = d_kill(dentry, parent);
dentry = dentry_kill(dentry, 1);
}
}
@ -617,8 +620,6 @@ static void shrink_dentry_list(struct list_head *list)
rcu_read_lock();
for (;;) {
struct dentry *parent;
dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
if (&dentry->d_lru == list)
break; /* empty */
@ -639,24 +640,10 @@ static void shrink_dentry_list(struct list_head *list)
continue;
}
if (!spin_trylock(&dcache_inode_lock)) {
relock:
spin_unlock(&dentry->d_lock);
cpu_relax();
continue;
}
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_lru_del(dentry);
rcu_read_unlock();
prune_one_dentry(dentry, parent);
try_prune_one_dentry(dentry);
rcu_read_lock();
}
rcu_read_unlock();