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author | Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> | 2009-06-07 18:39:32 +0200 |
---|---|---|
committer | Al Viro <viro@zeniv.linux.org.uk> | 2009-06-12 03:36:18 +0200 |
commit | e59399d0102c1813cec48db5cebe1750313f88a0 (patch) | |
tree | cd4fde6b5c442ede5d00b9640d3a545f847aeb8c /fs/nilfs2/the_nilfs.c | |
parent | nilfs2: simplify remaining sget() use (diff) | |
download | linux-e59399d0102c1813cec48db5cebe1750313f88a0.tar.xz linux-e59399d0102c1813cec48db5cebe1750313f88a0.zip |
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.c')
-rw-r--r-- | fs/nilfs2/the_nilfs.c | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c index 221953bfc859..06e8dfd538d6 100644 --- a/fs/nilfs2/the_nilfs.c +++ b/fs/nilfs2/the_nilfs.c @@ -72,6 +72,7 @@ static struct the_nilfs *alloc_nilfs(struct block_device *bdev) atomic_set(&nilfs->ns_writer_refcount, -1); atomic_set(&nilfs->ns_ndirtyblks, 0); init_rwsem(&nilfs->ns_sem); + init_rwsem(&nilfs->ns_super_sem); mutex_init(&nilfs->ns_writer_mutex); INIT_LIST_HEAD(&nilfs->ns_list); INIT_LIST_HEAD(&nilfs->ns_supers); @@ -681,10 +682,10 @@ struct nilfs_sb_info *nilfs_find_sbinfo(struct the_nilfs *nilfs, { struct nilfs_sb_info *sbi; - down_read(&nilfs->ns_sem); + down_read(&nilfs->ns_super_sem); /* * The SNAPSHOT flag and sb->s_flags are supposed to be - * protected with nilfs->ns_sem. + * protected with nilfs->ns_super_sem. */ sbi = nilfs->ns_current; if (rw_mount) { @@ -705,12 +706,12 @@ struct nilfs_sb_info *nilfs_find_sbinfo(struct the_nilfs *nilfs, goto found; /* snapshot mount */ } out: - up_read(&nilfs->ns_sem); + up_read(&nilfs->ns_super_sem); return NULL; found: atomic_inc(&sbi->s_count); - up_read(&nilfs->ns_sem); + up_read(&nilfs->ns_super_sem); return sbi; } @@ -720,7 +721,7 @@ int nilfs_checkpoint_is_mounted(struct the_nilfs *nilfs, __u64 cno, struct nilfs_sb_info *sbi; int ret = 0; - down_read(&nilfs->ns_sem); + down_read(&nilfs->ns_super_sem); if (cno == 0 || cno > nilfs->ns_cno) goto out_unlock; @@ -737,6 +738,6 @@ int nilfs_checkpoint_is_mounted(struct the_nilfs *nilfs, __u64 cno, ret++; out_unlock: - up_read(&nilfs->ns_sem); + up_read(&nilfs->ns_super_sem); return ret; } |