From 6f61076406251626be39651d114fac412b1e0c39 Mon Sep 17 00:00:00 2001 From: Louis Rilling Date: Mon, 16 Jun 2008 19:00:58 +0200 Subject: configfs: Introduce configfs_dirent_lock This patch introduces configfs_dirent_lock spinlock to protect configfs_dirent traversals against linkage mutations (add/del/move). This will allow configfs_detach_prep() to avoid locking i_mutexes. Locking rules for configfs_dirent linkage mutations are the same plus the requirement of taking configfs_dirent_lock. For configfs_dirent walking, one can either take appropriate i_mutex as before, or take configfs_dirent_lock. The spinlock could actually be a mutex, but the critical sections are either O(1) or should not be too long (default groups walking in last patch). ChangeLog: - Clarify the comment on configfs_dirent_lock usage - Move sd->s_element init before linking the new dirent - In lseek(), do not release configfs_dirent_lock before the dirent is relinked. Signed-off-by: Louis Rilling Signed-off-by: Joel Becker --- fs/configfs/configfs_internal.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'fs/configfs/configfs_internal.h') diff --git a/fs/configfs/configfs_internal.h b/fs/configfs/configfs_internal.h index cca98609aa7f..5a33b58e66da 100644 --- a/fs/configfs/configfs_internal.h +++ b/fs/configfs/configfs_internal.h @@ -26,6 +26,7 @@ #include #include +#include struct configfs_dirent { atomic_t s_count; @@ -49,6 +50,8 @@ struct configfs_dirent { #define CONFIGFS_USET_DROPPING 0x0100 #define CONFIGFS_NOT_PINNED (CONFIGFS_ITEM_ATTR) +extern spinlock_t configfs_dirent_lock; + extern struct vfsmount * configfs_mount; extern struct kmem_cache *configfs_dir_cachep; -- cgit v1.2.2 From 6d8344baee99402de58b5fa5dfea197242955c15 Mon Sep 17 00:00:00 2001 From: Louis Rilling Date: Mon, 16 Jun 2008 19:01:02 +0200 Subject: configfs: Fix failing mkdir() making racing rmdir() fail When fixing the rename() vs rmdir() deadlock, we stopped locking default groups' inodes in configfs_detach_prep(), letting racing mkdir() in default groups proceed concurrently. This enables races like below happen, which leads to a failing mkdir() making rmdir() fail, despite the group to remove having no user-created directory under it in the end. process A: process B: /* PWD=A/B */ mkdir("C") make_item("C") attach_group("C") rmdir("A") detach_prep("A") detach_prep("B") error because of "C" return -ENOTEMPTY attach_group("C/D") error (eg -ENOMEM) return -ENOMEM This patch prevents such scenarii by making rmdir() wait as long as detach_prep() fails because a racing mkdir() is in the middle of attach_group(). To achieve this, mkdir() sets a flag CONFIGFS_USET_IN_MKDIR in parent's configfs_dirent before calling attach_group(), and clears the flag once attach_group() is done. detach_prep() fails with -EAGAIN whenever the flag is hit and returns the guilty inode's mutex so that rmdir() can wait on it. Signed-off-by: Louis Rilling Signed-off-by: Joel Becker --- fs/configfs/configfs_internal.h | 1 + 1 file changed, 1 insertion(+) (limited to 'fs/configfs/configfs_internal.h') diff --git a/fs/configfs/configfs_internal.h b/fs/configfs/configfs_internal.h index 5a33b58e66da..da015c12e3ea 100644 --- a/fs/configfs/configfs_internal.h +++ b/fs/configfs/configfs_internal.h @@ -48,6 +48,7 @@ struct configfs_dirent { #define CONFIGFS_USET_DIR 0x0040 #define CONFIGFS_USET_DEFAULT 0x0080 #define CONFIGFS_USET_DROPPING 0x0100 +#define CONFIGFS_USET_IN_MKDIR 0x0200 #define CONFIGFS_NOT_PINNED (CONFIGFS_ITEM_ATTR) extern spinlock_t configfs_dirent_lock; -- cgit v1.2.2