87 lines
2.3 KiB
Diff
87 lines
2.3 KiB
Diff
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From: Al Viro <viro@zeniv.linux.org.uk>
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Date: Sun, 26 Oct 2014 19:31:10 -0400
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Subject: [PATCH] deal with deadlock in d_walk()
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... by not hitting rename_retry for reasons other than rename having
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happened. In other words, do _not_ restart when finding that
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between unlocking the child and locking the parent the former got
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into __dentry_kill(). Skip the killed siblings instead...
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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---
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fs/dcache.c | 31 ++++++++++++++++---------------
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1 file changed, 16 insertions(+), 15 deletions(-)
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diff --git a/fs/dcache.c b/fs/dcache.c
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index c3ea5b765f6a..71acf8d6f2be 100644
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--- a/fs/dcache.c
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+++ b/fs/dcache.c
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@@ -495,7 +495,7 @@ static void __dentry_kill(struct dentry *dentry)
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}
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/* if it was on the hash then remove it */
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__d_drop(dentry);
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- list_del(&dentry->d_child);
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+ __list_del_entry(&dentry->d_child);
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/*
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* Inform d_walk() that we are no longer attached to the
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* dentry tree
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@@ -1082,33 +1082,31 @@ resume:
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/*
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* All done at this level ... ascend and resume the search.
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*/
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+ rcu_read_lock();
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+ascend:
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if (this_parent != parent) {
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struct dentry *child = this_parent;
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this_parent = child->d_parent;
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- rcu_read_lock();
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spin_unlock(&child->d_lock);
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spin_lock(&this_parent->d_lock);
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- /*
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- * might go back up the wrong parent if we have had a rename
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- * or deletion
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- */
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- if (this_parent != child->d_parent ||
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- (child->d_flags & DCACHE_DENTRY_KILLED) ||
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- need_seqretry(&rename_lock, seq)) {
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- spin_unlock(&this_parent->d_lock);
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- rcu_read_unlock();
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+ /* might go back up the wrong parent if we have had a rename. */
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+ if (need_seqretry(&rename_lock, seq))
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goto rename_retry;
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+ next = child->d_child.next;
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+ while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED)) {
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+ if (next == &this_parent->d_subdirs)
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+ goto ascend;
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+ child = list_entry(next, struct dentry, d_child);
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+ next = next->next;
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}
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rcu_read_unlock();
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- next = child->d_child.next;
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goto resume;
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}
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- if (need_seqretry(&rename_lock, seq)) {
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- spin_unlock(&this_parent->d_lock);
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+ if (need_seqretry(&rename_lock, seq))
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goto rename_retry;
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- }
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+ rcu_read_unlock();
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if (finish)
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finish(data);
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@@ -1118,6 +1116,9 @@ out_unlock:
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return;
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rename_retry:
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+ spin_unlock(&this_parent->d_lock);
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+ rcu_read_unlock();
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+ BUG_ON(seq & 1);
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if (!retry)
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return;
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seq = 1;
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--
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2.1.0
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