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authorRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>2009-06-07 18:39:32 +0200
committerAl Viro <viro@zeniv.linux.org.uk>2009-06-12 03:36:18 +0200
commite59399d0102c1813cec48db5cebe1750313f88a0 (patch)
treecd4fde6b5c442ede5d00b9640d3a545f847aeb8c /fs/nilfs2/the_nilfs.c
parentnilfs2: simplify remaining sget() use (diff)
downloadlinux-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.c13
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;
}