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authorAl Viro <viro@zeniv.linux.org.uk>2014-10-26 19:31:10 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-04-29 10:34:00 +0200
commit5f03ac13d87590b0ee879c77e68df63a3d9b3e07 (patch)
tree9985fd0b9bccdd3e484727ec521573f2833d08e5 /fs
parent6637ecd306a94a03dd5b8e4e8d3f260d9877c5b0 (diff)
downloadlinux-linaro-stable-5f03ac13d87590b0ee879c77e68df63a3d9b3e07.tar.gz
deal with deadlock in d_walk()
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 3.10 refer to the work of Ben Hutchings in 3.2: - As we only have try_to_ascend() and not d_walk(), apply this change to all callers of try_to_ascend() - 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>
Diffstat (limited to 'fs')
-rw-r--r--fs/dcache.c102
1 files changed, 62 insertions, 40 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index b3cb521809e9..b1b8a7e9db0c 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -364,9 +364,9 @@ static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
__releases(parent->d_lock)
__releases(dentry->d_inode->i_lock)
{
- list_del(&dentry->d_child);
+ __list_del_entry(&dentry->d_child);
/*
- * Inform try_to_ascend() that we are no longer attached to the
+ * Inform ascending readers that we are no longer attached to the
* dentry tree
*/
dentry->d_flags |= DCACHE_DENTRY_KILLED;
@@ -988,35 +988,6 @@ void shrink_dcache_for_umount(struct super_block *sb)
}
/*
- * This tries to ascend one level of parenthood, but
- * we can race with renaming, so we need to re-check
- * the parenthood after dropping the lock and check
- * that the sequence number still matches.
- */
-static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq)
-{
- struct dentry *new = old->d_parent;
-
- rcu_read_lock();
- spin_unlock(&old->d_lock);
- spin_lock(&new->d_lock);
-
- /*
- * might go back up the wrong parent if we have had a rename
- * or deletion
- */
- if (new != old->d_parent ||
- (old->d_flags & DCACHE_DENTRY_KILLED) ||
- (!locked && read_seqretry(&rename_lock, seq))) {
- spin_unlock(&new->d_lock);
- new = NULL;
- }
- rcu_read_unlock();
- return new;
-}
-
-
-/*
* Search for at least 1 mount point in the dentry's subdirs.
* We descend to the next level whenever the d_subdirs
* list is non-empty and continue searching.
@@ -1070,17 +1041,32 @@ 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 = try_to_ascend(this_parent, locked, seq);
- if (!this_parent)
+ this_parent = child->d_parent;
+
+ spin_unlock(&child->d_lock);
+ spin_lock(&this_parent->d_lock);
+
+ /* might go back up the wrong parent if we have had a rename. */
+ if (!locked && read_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();
goto resume;
}
- spin_unlock(&this_parent->d_lock);
if (!locked && read_seqretry(&rename_lock, seq))
goto rename_retry;
+ spin_unlock(&this_parent->d_lock);
+ rcu_read_unlock();
if (locked)
write_sequnlock(&rename_lock);
return 0; /* No mount points found in tree */
@@ -1092,6 +1078,8 @@ positive:
return 1;
rename_retry:
+ spin_unlock(&this_parent->d_lock);
+ rcu_read_unlock();
if (locked)
goto again;
locked = 1;
@@ -1177,23 +1165,40 @@ 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 = try_to_ascend(this_parent, locked, seq);
- if (!this_parent)
+ this_parent = child->d_parent;
+
+ spin_unlock(&child->d_lock);
+ spin_lock(&this_parent->d_lock);
+
+ /* might go back up the wrong parent if we have had a rename. */
+ if (!locked && read_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();
goto resume;
}
out:
- spin_unlock(&this_parent->d_lock);
if (!locked && read_seqretry(&rename_lock, seq))
goto rename_retry;
+ spin_unlock(&this_parent->d_lock);
+ rcu_read_unlock();
if (locked)
write_sequnlock(&rename_lock);
return found;
rename_retry:
+ spin_unlock(&this_parent->d_lock);
+ rcu_read_unlock();
if (found)
return found;
if (locked)
@@ -2954,26 +2959,43 @@ resume:
}
spin_unlock(&dentry->d_lock);
}
+ rcu_read_lock();
+ascend:
if (this_parent != root) {
struct dentry *child = this_parent;
if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
this_parent->d_flags |= DCACHE_GENOCIDE;
this_parent->d_count--;
}
- this_parent = try_to_ascend(this_parent, locked, seq);
- if (!this_parent)
+ this_parent = child->d_parent;
+
+ spin_unlock(&child->d_lock);
+ spin_lock(&this_parent->d_lock);
+
+ /* might go back up the wrong parent if we have had a rename. */
+ if (!locked && read_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();
goto resume;
}
- spin_unlock(&this_parent->d_lock);
if (!locked && read_seqretry(&rename_lock, seq))
goto rename_retry;
+ spin_unlock(&this_parent->d_lock);
+ rcu_read_unlock();
if (locked)
write_sequnlock(&rename_lock);
return;
rename_retry:
+ spin_unlock(&this_parent->d_lock);
+ rcu_read_unlock();
if (locked)
goto again;
locked = 1;