74 lines
2.1 KiB
Diff
74 lines
2.1 KiB
Diff
From: Al Viro <viro@zeniv.linux.org.uk>
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Date: Fri, 23 Feb 2018 21:25:42 -0500
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Subject: [PATCH 06/17] get rid of trylock loop around dentry_kill()
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.16/older/patches-4.16.7-rt1.tar.xz
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Upstream commit f657a666fd1b1b9fe59963943c74c245ae66f4cc
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In case when trylock in there fails, deal with it directly in
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dentry_kill(). Note that in cases when we drop and retake
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->d_lock, we need to recheck whether to retain the dentry.
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Another thing is that dropping/retaking ->d_lock might have
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ended up with negative dentry turning into positive; that,
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of course, can happen only once...
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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fs/dcache.c | 34 +++++++++++++++++++++++++++-------
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1 file changed, 27 insertions(+), 7 deletions(-)
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--- a/fs/dcache.c
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+++ b/fs/dcache.c
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@@ -651,23 +651,43 @@ static struct dentry *dentry_kill(struct
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struct dentry *parent = NULL;
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if (inode && unlikely(!spin_trylock(&inode->i_lock)))
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- goto failed;
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+ goto slow_positive;
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if (!IS_ROOT(dentry)) {
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parent = dentry->d_parent;
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if (unlikely(!spin_trylock(&parent->d_lock))) {
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- if (inode)
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- spin_unlock(&inode->i_lock);
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- goto failed;
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+ parent = __lock_parent(dentry);
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+ if (likely(inode || !dentry->d_inode))
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+ goto got_locks;
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+ /* negative that became positive */
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+ if (parent)
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+ spin_unlock(&parent->d_lock);
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+ inode = dentry->d_inode;
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+ goto slow_positive;
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}
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}
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-
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__dentry_kill(dentry);
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return parent;
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-failed:
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+slow_positive:
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+ spin_unlock(&dentry->d_lock);
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+ spin_lock(&inode->i_lock);
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+ spin_lock(&dentry->d_lock);
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+ parent = lock_parent(dentry);
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+got_locks:
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+ if (unlikely(dentry->d_lockref.count != 1)) {
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+ dentry->d_lockref.count--;
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+ } else if (likely(!retain_dentry(dentry))) {
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+ __dentry_kill(dentry);
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+ return parent;
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+ }
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+ /* we are keeping it, after all */
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+ if (inode)
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+ spin_unlock(&inode->i_lock);
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+ if (parent)
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+ spin_unlock(&parent->d_lock);
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spin_unlock(&dentry->d_lock);
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- return dentry; /* try again with same dentry */
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+ return NULL;
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}
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/*
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