Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 3.14 36/51] deal with deadlock in d_walk() | Date | Fri, 15 May 2015 16:10:38 -0700 |
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3.14-stable review patch. If anyone has any objections, please let me know.
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From: Al Viro <viro@zeniv.linux.org.uk>
commit ca5358ef75fc69fee5322a38a340f5739d997c10 upstream.
... by not hitting rename_retry for reasons other than rename having happened. In other words, do _not_ restart when finding that between unlocking the child and locking the parent the former got into __dentry_kill(). Skip the killed siblings instead...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Ben Hutchings <ben@decadent.org.uk> [hujianyang: Backported to 3.14 refer to the work of Ben Hutchings in 3.2: - Adjust context to make __dentry_kill() apply to d_kill()] Signed-off-by: hujianyang <hujianyang@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- fs/dcache.c | 31 ++++++++++++++++--------------- 1 file changed, 16 insertions(+), 15 deletions(-)
--- a/fs/dcache.c +++ b/fs/dcache.c @@ -435,7 +435,7 @@ static struct dentry *d_kill(struct dent __releases(parent->d_lock) __releases(dentry->d_inode->i_lock) { - list_del(&dentry->d_child); + __list_del_entry(&dentry->d_child); /* * Inform d_walk() that we are no longer attached to the * dentry tree @@ -1123,33 +1123,31 @@ resume: /* * All done at this level ... ascend and resume the search. */ + rcu_read_lock(); +ascend: if (this_parent != parent) { struct dentry *child = this_parent; this_parent = child->d_parent; - rcu_read_lock(); spin_unlock(&child->d_lock); spin_lock(&this_parent->d_lock); - /* - * might go back up the wrong parent if we have had a rename - * or deletion - */ - if (this_parent != child->d_parent || - (child->d_flags & DCACHE_DENTRY_KILLED) || - need_seqretry(&rename_lock, seq)) { - spin_unlock(&this_parent->d_lock); - rcu_read_unlock(); + /* might go back up the wrong parent if we have had a rename. */ + if (need_seqretry(&rename_lock, seq)) goto rename_retry; + next = child->d_child.next; + while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED)) { + if (next == &this_parent->d_subdirs) + goto ascend; + child = list_entry(next, struct dentry, d_child); + next = next->next; } rcu_read_unlock(); - next = child->d_child.next; goto resume; } - if (need_seqretry(&rename_lock, seq)) { - spin_unlock(&this_parent->d_lock); + if (need_seqretry(&rename_lock, seq)) goto rename_retry; - } + rcu_read_unlock(); if (finish) finish(data); @@ -1159,6 +1157,9 @@ out_unlock: return; rename_retry: + spin_unlock(&this_parent->d_lock); + rcu_read_unlock(); + BUG_ON(seq & 1); if (!retry) return; seq = 1;
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