diff options
author | Al Viro <viro@zeniv.linux.org.uk> | 2014-10-26 19:31:10 -0400 |
---|---|---|
committer | Zefan Li <lizefan@huawei.com> | 2015-04-14 17:33:58 +0800 |
commit | a91da0b39a785448ef420c4ac389d03f4743a836 (patch) | |
tree | f18117976b4806af88a387d776cddc46782db1fd /fs | |
parent | 6fd17def6d964c81205230e02b4208c653106d51 (diff) |
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>
[bwh: Backported to 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: Ben Hutchings <ben@decadent.org.uk>
[lizf: Backported to 3.4: fold the fix 2d5a2e6775fa in 3.2.y into this patch]
Signed-off-by: Zefan Li <lizefan@huawei.com>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/dcache.c | 105 |
1 files changed, 65 insertions, 40 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index 2ccc64681b16..8038a780696f 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -368,9 +368,9 @@ 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; @@ -1011,34 +1011,6 @@ 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. @@ -1094,30 +1066,48 @@ 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 */ positive: if (!locked && read_seqretry(&rename_lock, seq)) - goto rename_retry; + goto rename_retry_unlocked; if (locked) write_sequnlock(&rename_lock); return 1; rename_retry: + spin_unlock(&this_parent->d_lock); + rcu_read_unlock(); if (locked) goto again; +rename_retry_unlocked: locked = 1; write_seqlock(&rename_lock); goto again; @@ -1182,6 +1172,7 @@ resume: */ if (found && need_resched()) { spin_unlock(&dentry->d_lock); + rcu_read_lock(); goto out; } @@ -1201,23 +1192,40 @@ 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) @@ -2955,26 +2963,43 @@ 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; 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