2.6.38-stable review patch. If anyone has any objections, please let us know.
------------------ From: Linus Torvalds <[email protected]> commit c826cb7dfce80512c26c984350077a25046bd215 upstream. This creates a helper function for he "try to ascend into the parent directory" case, which was written out in triplicate before. With all the locking and subtle sequence number stuff, we really don't want to duplicate that kind of code. Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/dcache.c | 88 +++++++++++++++++++++++++----------------------------------- 1 file changed, 37 insertions(+), 51 deletions(-) --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1012,6 +1012,34 @@ void shrink_dcache_for_umount(struct sup } /* + * 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 || + (!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. @@ -1066,24 +1094,10 @@ resume: * All done at this level ... ascend and resume the search. */ if (this_parent != parent) { - struct dentry *tmp; - struct dentry *child; - - tmp = this_parent->d_parent; - rcu_read_lock(); - spin_unlock(&this_parent->d_lock); - child = this_parent; - this_parent = tmp; - 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 || - (!locked && read_seqretry(&rename_lock, seq))) { - spin_unlock(&this_parent->d_lock); - rcu_read_unlock(); + struct dentry *child = this_parent; + this_parent = try_to_ascend(this_parent, locked, seq); + if (!this_parent) goto rename_retry; - } - rcu_read_unlock(); next = child->d_u.d_child.next; goto resume; } @@ -1181,24 +1195,10 @@ resume: * All done at this level ... ascend and resume the search. */ if (this_parent != parent) { - struct dentry *tmp; - struct dentry *child; - - tmp = this_parent->d_parent; - rcu_read_lock(); - spin_unlock(&this_parent->d_lock); - child = this_parent; - this_parent = tmp; - 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 || - (!locked && read_seqretry(&rename_lock, seq))) { - spin_unlock(&this_parent->d_lock); - rcu_read_unlock(); + struct dentry *child = this_parent; + this_parent = try_to_ascend(this_parent, locked, seq); + if (!this_parent) goto rename_retry; - } - rcu_read_unlock(); next = child->d_u.d_child.next; goto resume; } @@ -2942,28 +2942,14 @@ resume: spin_unlock(&dentry->d_lock); } if (this_parent != root) { - struct dentry *tmp; - struct dentry *child; - - tmp = this_parent->d_parent; + struct dentry *child = this_parent; if (!(this_parent->d_flags & DCACHE_GENOCIDE)) { this_parent->d_flags |= DCACHE_GENOCIDE; this_parent->d_count--; } - rcu_read_lock(); - spin_unlock(&this_parent->d_lock); - child = this_parent; - this_parent = tmp; - 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 || - (!locked && read_seqretry(&rename_lock, seq))) { - spin_unlock(&this_parent->d_lock); - rcu_read_unlock(); + this_parent = try_to_ascend(this_parent, locked, seq); + if (!this_parent) goto rename_retry; - } - rcu_read_unlock(); next = child->d_u.d_child.next; goto resume; } _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
