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get rid of trylock loop around dentry_kill()

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In case when trylock in there fails, deal with it directly in
dentry_kill().  Note that in cases when we drop and retake
->d_lock, we need to recheck whether to retain the dentry.
Another thing is that dropping/retaking ->d_lock might have
ended up with negative dentry turning into positive; that,
of course, can happen only once...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2018-02-23 21:25:42 -05:00
parent 62d9956cef
commit f657a666fd
1 changed files with 27 additions and 7 deletions
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34
fs/dcache.c
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@ -651,23 +651,43 @@ static struct dentry *dentry_kill(struct dentry *dentry)
struct dentry *parent = NULL;
if (inode && unlikely(!spin_trylock(&inode->i_lock)))
goto failed;
goto slow_positive;
if (!IS_ROOT(dentry)) {
parent = dentry->d_parent;
if (unlikely(!spin_trylock(&parent->d_lock))) {
if (inode)
spin_unlock(&inode->i_lock);
goto failed;
parent = __lock_parent(dentry);
if (likely(inode || !dentry->d_inode))
goto got_locks;
/* negative that became positive */
if (parent)
spin_unlock(&parent->d_lock);
inode = dentry->d_inode;
goto slow_positive;
}
}
__dentry_kill(dentry);
return parent;
failed:
slow_positive:
spin_unlock(&dentry->d_lock);
return dentry; /* try again with same dentry */
spin_lock(&inode->i_lock);
spin_lock(&dentry->d_lock);
parent = lock_parent(dentry);
got_locks:
if (unlikely(dentry->d_lockref.count != 1)) {
dentry->d_lockref.count--;
} else if (likely(!retain_dentry(dentry))) {
__dentry_kill(dentry);
return parent;
}
/* we are keeping it, after all */
if (inode)
spin_unlock(&inode->i_lock);
if (parent)
spin_unlock(&parent->d_lock);
spin_unlock(&dentry->d_lock);
return NULL;
}
/*