The behavior was removed in 18e9e5104fcd9a973ffe3eed3816c87f2a1b6cd2
noting that this was a better idea than using a counter. However, this
behavior is actually wanted if multiple applications want to freeze
concurrently while remaining non-racy.
This patch reintroduces this feature by using a counter.
---
fs/super.c | 15 +++++++++++----
include/linux/fs.h | 1 +
2 files changed, 12 insertions(+), 4 deletions(-)
diff --git a/fs/super.c b/fs/super.c
index 74914b1..9fa8ca1 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -231,6 +231,7 @@ static struct super_block *alloc_super(struct
file_system_type *type, int flags)
*/
down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
s->s_count = 1;
+ s->s_freezers = 0;
atomic_set(&s->s_active, 1);
mutex_init(&s->s_vfs_rename_mutex);
lockdep_set_class(&s->s_vfs_rename_mutex, &type-
>s_vfs_rename_key);
@@ -1275,12 +1276,12 @@ int freeze_super(struct super_block *sb)
{
int ret;
+ sb->s_freezers++;
+ if (sb->s_writers.frozen != SB_UNFROZEN)
+ return 0;
+
atomic_inc(&sb->s_active);
down_write(&sb->s_umount);
- if (sb->s_writers.frozen != SB_UNFROZEN) {
- deactivate_locked_super(sb);
- return -EBUSY;
- }
if (!(sb->s_flags & MS_BORN)) {
up_write(&sb->s_umount);
@@ -1338,14 +1339,20 @@ EXPORT_SYMBOL(freeze_super);
* @sb: the super to thaw
*
* Unlocks the filesystem and marks it writeable again after
freeze_super().
+ * Since nesting freezes is allowed, only the last freeze actually
unlocks.
*/
int thaw_super(struct super_block *sb)
{
int error;
+ sb->s_freezers--;
+ if (sb->s_freezers > 0)
+ return 0;
+
down_write(&sb->s_umount);
if (sb->s_writers.frozen == SB_UNFROZEN) {
up_write(&sb->s_umount);
+ sb->s_freezers++;
return -EINVAL;
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e514f76..c045e2a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1333,6 +1333,7 @@ struct super_block {
struct quota_info s_dquot; /* Diskquota specific
options */
struct sb_writers s_writers;
+ int s_freezers;
char s_id[32]; /* Informational
name */
u8 s_uuid[16]; /* UUID */
--
2.8.0
--
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