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d_prune_alias(): just lock the parent and call __dentry_kill()

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The only reason for games with ->d_prune() was __d_drop(), which
was needed only to force dput() into killing the sucker off.

Note that lock_parent() can be called under ->i_lock and won't
drop it, so dentry is safe from somebody managing to kill it
under us - it won't happen while we are holding ->i_lock.

__dentry_kill() is called only with ->d_lockref.count being 0
(here and when picked from shrink list) or 1 (dput() and dropping
the ancestors in shrink_dentry_list()), so it will never be called
twice - the first thing it's doing is making ->d_lockref.count
negative and once that happens, nothing will increment it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2014-05-30 11:25:30 -04:00
parent bbd5192412
commit 29355c3904
1 changed files with 7 additions and 14 deletions
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21
fs/dcache.c
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@ -770,20 +770,13 @@ restart:
hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
spin_lock(&dentry->d_lock);
if (!dentry->d_lockref.count) {
/*
* inform the fs via d_prune that this dentry
* is about to be unhashed and destroyed.
*/
if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
!d_unhashed(dentry))
dentry->d_op->d_prune(dentry);
__dget_dlock(dentry);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&inode->i_lock);
dput(dentry);
goto restart;
struct dentry *parent = lock_parent(dentry);
if (likely(!dentry->d_lockref.count)) {
__dentry_kill(dentry);
goto restart;
}
if (parent)
spin_unlock(&parent->d_lock);
}
spin_unlock(&dentry->d_lock);
}