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fs: split __shrink_dcache_sb 

Currently __shrink_dcache_sb has an extremly awkward calling convention
because it tries to please very different callers.  Split out the
main loop into a shrink_dentry_list helper, which gets called directly
from shrink_dcache_sb for the cases where all dentries need to be pruned,
or from __shrink_dcache_sb for pruning only a certain number of dentries.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Christoph Hellwig 2010-10-10 05:36:25 -04:00 committed by Al Viro
parent 265ac90230
commit 3049cfe24e
1 changed files with 67 additions and 60 deletions
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127
fs/dcache.c
View File

@ -459,66 +459,20 @@ static void prune_one_dentry(struct dentry * dentry)
}
}
/*
* Shrink the dentry LRU on a given superblock.
* @sb : superblock to shrink dentry LRU.
* @count: If count is NULL, we prune all dentries on superblock.
* @flags: If flags is non-zero, we need to do special processing based on
* which flags are set. This means we don't need to maintain multiple
* similar copies of this loop.
*/
static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
static void shrink_dentry_list(struct list_head *list)
{
LIST_HEAD(referenced);
LIST_HEAD(tmp);
struct dentry *dentry;
int cnt = 0;
BUG_ON(!sb);
BUG_ON((flags & DCACHE_REFERENCED) && count == NULL);
spin_lock(&dcache_lock);
if (count != NULL)
/* called from prune_dcache() and shrink_dcache_parent() */
cnt = *count;
restart:
if (count == NULL)
list_splice_init(&sb->s_dentry_lru, &tmp);
else {
while (!list_empty(&sb->s_dentry_lru)) {
dentry = list_entry(sb->s_dentry_lru.prev,
struct dentry, d_lru);
BUG_ON(dentry->d_sb != sb);
spin_lock(&dentry->d_lock);
/*
* If we are honouring the DCACHE_REFERENCED flag and
* the dentry has this flag set, don't free it. Clear
* the flag and put it back on the LRU.
*/
if ((flags & DCACHE_REFERENCED)
&& (dentry->d_flags & DCACHE_REFERENCED)) {
dentry->d_flags &= ~DCACHE_REFERENCED;
list_move(&dentry->d_lru, &referenced);
spin_unlock(&dentry->d_lock);
} else {
list_move_tail(&dentry->d_lru, &tmp);
spin_unlock(&dentry->d_lock);
cnt--;
if (!cnt)
break;
}
cond_resched_lock(&dcache_lock);
}
}
while (!list_empty(&tmp)) {
dentry = list_entry(tmp.prev, struct dentry, d_lru);
while (!list_empty(list)) {
dentry = list_entry(list->prev, struct dentry, d_lru);
dentry_lru_del_init(dentry);
spin_lock(&dentry->d_lock);
/*
* We found an inuse dentry which was not removed from
* the LRU because of laziness during lookup. Do not free
* it - just keep it off the LRU list.
*/
spin_lock(&dentry->d_lock);
if (atomic_read(&dentry->d_count)) {
spin_unlock(&dentry->d_lock);
continue;
@ -527,13 +481,60 @@ restart:
/* dentry->d_lock was dropped in prune_one_dentry() */
cond_resched_lock(&dcache_lock);
}
if (count == NULL && !list_empty(&sb->s_dentry_lru))
goto restart;
if (count != NULL)
*count = cnt;
}
/**
* __shrink_dcache_sb - shrink the dentry LRU on a given superblock
* @sb: superblock to shrink dentry LRU.
* @count: number of entries to prune
* @flags: flags to control the dentry processing
*
* If flags contains DCACHE_REFERENCED reference dentries will not be pruned.
*/
static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
{
/* called from prune_dcache() and shrink_dcache_parent() */
struct dentry *dentry;
LIST_HEAD(referenced);
LIST_HEAD(tmp);
int cnt = *count;
spin_lock(&dcache_lock);
while (!list_empty(&sb->s_dentry_lru)) {
dentry = list_entry(sb->s_dentry_lru.prev,
struct dentry, d_lru);
BUG_ON(dentry->d_sb != sb);
/*
* If we are honouring the DCACHE_REFERENCED flag and the
* dentry has this flag set, don't free it. Clear the flag
* and put it back on the LRU.
*/
if (flags & DCACHE_REFERENCED) {
spin_lock(&dentry->d_lock);
if (dentry->d_flags & DCACHE_REFERENCED) {
dentry->d_flags &= ~DCACHE_REFERENCED;
list_move(&dentry->d_lru, &referenced);
spin_unlock(&dentry->d_lock);
cond_resched_lock(&dcache_lock);
continue;
}
spin_unlock(&dentry->d_lock);
}
list_move_tail(&dentry->d_lru, &tmp);
if (!--cnt)
break;
cond_resched_lock(&dcache_lock);
}
*count = cnt;
shrink_dentry_list(&tmp);
if (!list_empty(&referenced))
list_splice(&referenced, &sb->s_dentry_lru);
spin_unlock(&dcache_lock);
}
/**
@ -619,13 +620,19 @@ static void prune_dcache(int count)
* shrink_dcache_sb - shrink dcache for a superblock
* @sb: superblock
*
* Shrink the dcache for the specified super block. This
* is used to free the dcache before unmounting a file
* system
* Shrink the dcache for the specified super block. This is used to free
* the dcache before unmounting a file system.
*/
void shrink_dcache_sb(struct super_block * sb)
void shrink_dcache_sb(struct super_block *sb)
{
__shrink_dcache_sb(sb, NULL, 0);
LIST_HEAD(tmp);
spin_lock(&dcache_lock);
while (!list_empty(&sb->s_dentry_lru)) {
list_splice_init(&sb->s_dentry_lru, &tmp);
shrink_dentry_list(&tmp);
}
spin_unlock(&dcache_lock);
}
EXPORT_SYMBOL(shrink_dcache_sb);