From e59399d0102c1813cec48db5cebe1750313f88a0 Mon Sep 17 00:00:00 2001 From: Ryusuke Konishi Date: Mon, 8 Jun 2009 01:39:32 +0900 Subject: nilfs2: correct exclusion control in nilfs_remount function nilfs_remount() changes mount state of a superblock instance. Even though nilfs accesses other superblock instances during mount or remount, the mount state was not properly protected in nilfs_remount(). Moreover, nilfs_remount() has a lock order reversal problem; nilfs_get_sb() holds: 1. bdev->bd_mount_sem 2. sb->s_umount (sget acquires) and nilfs_remount() holds: 1. sb->s_umount (locked by the caller in vfs) 2. bdev->bd_mount_sem To avoid these problems, this patch divides a semaphore protecting super block instances from nilfs->ns_sem, and applies it to the mount state protection in nilfs_remount(). With this change, bd_mount_sem use is removed from nilfs_remount() and the lock order reversal will be resolved. And the new rw-semaphore, nilfs->ns_super_sem will properly protect the mount state except the modification from nilfs_error function. Signed-off-by: Ryusuke Konishi Signed-off-by: Al Viro --- fs/nilfs2/the_nilfs.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'fs/nilfs2/the_nilfs.h') diff --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h index be4c040fd629..d0cf4fb7c9ce 100644 --- a/fs/nilfs2/the_nilfs.h +++ b/fs/nilfs2/the_nilfs.h @@ -48,6 +48,7 @@ enum { * @ns_bdi: backing dev info * @ns_writer: back pointer to writable nilfs_sb_info * @ns_sem: semaphore for shared states + * @ns_super_sem: semaphore for global operations across super block instances * @ns_writer_mutex: mutex protecting ns_writer attach/detach * @ns_writer_refcount: number of referrers on ns_writer * @ns_current: back pointer to current mount @@ -96,10 +97,15 @@ struct the_nilfs { struct backing_dev_info *ns_bdi; struct nilfs_sb_info *ns_writer; struct rw_semaphore ns_sem; + struct rw_semaphore ns_super_sem; struct mutex ns_writer_mutex; atomic_t ns_writer_refcount; + /* + * components protected by ns_super_sem + */ struct nilfs_sb_info *ns_current; + struct list_head ns_supers; /* * used for @@ -113,7 +119,6 @@ struct the_nilfs { time_t ns_sbwtime[2]; unsigned ns_sbsize; unsigned ns_mount_state; - struct list_head ns_supers; /* * Following fields are dedicated to a writable FS-instance. -- cgit