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| author | Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> | 2009-06-08 01:39:32 +0900 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2009-06-11 21:36:18 -0400 |
| commit | e59399d0102c1813cec48db5cebe1750313f88a0 (patch) | |
| tree | cd4fde6b5c442ede5d00b9640d3a545f847aeb8c /fs/nilfs2/the_nilfs.h | |
| parent | 6dd4740662405a68bb229ac2b9e0aeaaf2188bf2 (diff) | |
| download | linux-e59399d0102c1813cec48db5cebe1750313f88a0.tar.bz2 | |
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 <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/nilfs2/the_nilfs.h')
| -rw-r--r-- | fs/nilfs2/the_nilfs.h | 7 |
1 files changed, 6 insertions, 1 deletions
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. |