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btrfs: consolidate device_list_mutex in prepare_sprout to its parent

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btrfs_prepare_sprout() splices seed devices into its own struct fs_devices,
so that its parent function btrfs_init_new_device() can add the new sprout
device to fs_info->fs_devices.

Both btrfs_prepare_sprout() and btrfs_init_new_device() need
device_list_mutex. But they are holding it separately, thus create a
small race window. Close it and hold device_list_mutex across both
functions btrfs_init_new_device() and btrfs_prepare_sprout().

Split btrfs_prepare_sprout() into btrfs_init_sprout() and
btrfs_setup_sprout(). This split is essential because device_list_mutex
must not be held for allocations in btrfs_init_sprout() but must be held
for btrfs_setup_sprout(). So now a common device_list_mutex can be used
between btrfs_init_new_device() and btrfs_setup_sprout().

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Anand Jain 2021-11-09 17:51:58 +08:00 committed by David Sterba
parent fd8808097a
commit 849eae5e57
1 changed files with 51 additions and 18 deletions
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69
fs/btrfs/volumes.c
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@ -2431,21 +2431,15 @@ struct btrfs_device *btrfs_find_device_by_devspec(
return device;
}
/*
* does all the dirty work required for changing file system's UUID.
*/
static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info)
static struct btrfs_fs_devices *btrfs_init_sprout(struct btrfs_fs_info *fs_info)
{
struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
struct btrfs_fs_devices *old_devices;
struct btrfs_fs_devices *seed_devices;
struct btrfs_super_block *disk_super = fs_info->super_copy;
struct btrfs_device *device;
u64 super_flags;
lockdep_assert_held(&uuid_mutex);
if (!fs_devices->seeding)
return -EINVAL;
return ERR_PTR(-EINVAL);
/*
* Private copy of the seed devices, anchored at
@ -2453,7 +2447,7 @@ static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info)
*/
seed_devices = alloc_fs_devices(NULL, NULL);
if (IS_ERR(seed_devices))
return PTR_ERR(seed_devices);
return seed_devices;
/*
* It's necessary to retain a copy of the original seed fs_devices in
@ -2464,7 +2458,7 @@ static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info)
old_devices = clone_fs_devices(fs_devices);
if (IS_ERR(old_devices)) {
kfree(seed_devices);
return PTR_ERR(old_devices);
return old_devices;
}
list_add(&old_devices->fs_list, &fs_uuids);
@ -2475,7 +2469,41 @@ static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info)
INIT_LIST_HEAD(&seed_devices->alloc_list);
mutex_init(&seed_devices->device_list_mutex);
mutex_lock(&fs_devices->device_list_mutex);
return seed_devices;
}
/*
* Splice seed devices into the sprout fs_devices.
* Generate a new fsid for the sprouted read-write filesystem.
*/
static void btrfs_setup_sprout(struct btrfs_fs_info *fs_info,
struct btrfs_fs_devices *seed_devices)
{
struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
struct btrfs_super_block *disk_super = fs_info->super_copy;
struct btrfs_device *device;
u64 super_flags;
/*
* We are updating the fsid, the thread leading to device_list_add()
* could race, so uuid_mutex is needed.
*/
lockdep_assert_held(&uuid_mutex);
/*
* The threads listed below may traverse dev_list but can do that without
* device_list_mutex:
* - All device ops and balance - as we are in btrfs_exclop_start.
* - Various dev_list readers - are using RCU.
* - btrfs_ioctl_fitrim() - is using RCU.
*
* For-read threads as below are using device_list_mutex:
* - Readonly scrub btrfs_scrub_dev()
* - Readonly scrub btrfs_scrub_progress()
* - btrfs_get_dev_stats()
*/
lockdep_assert_held(&fs_devices->device_list_mutex);
list_splice_init_rcu(&fs_devices->devices, &seed_devices->devices,
synchronize_rcu);
list_for_each_entry(device, &seed_devices->devices, dev_list)
@ -2491,13 +2519,10 @@ static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info)
generate_random_uuid(fs_devices->fsid);
memcpy(fs_devices->metadata_uuid, fs_devices->fsid, BTRFS_FSID_SIZE);
memcpy(disk_super->fsid, fs_devices->fsid, BTRFS_FSID_SIZE);
mutex_unlock(&fs_devices->device_list_mutex);
super_flags = btrfs_super_flags(disk_super) &
~BTRFS_SUPER_FLAG_SEEDING;
btrfs_set_super_flags(disk_super, super_flags);
return 0;
}
/*
@ -2588,6 +2613,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
struct super_block *sb = fs_info->sb;
struct rcu_string *name;
struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
struct btrfs_fs_devices *seed_devices;
u64 orig_super_total_bytes;
u64 orig_super_num_devices;
int ret = 0;
@ -2671,18 +2697,25 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
if (seeding_dev) {
btrfs_clear_sb_rdonly(sb);
ret = btrfs_prepare_sprout(fs_info);
if (ret) {
/* GFP_KERNEL allocation must not be under device_list_mutex */
seed_devices = btrfs_init_sprout(fs_info);
if (IS_ERR(seed_devices)) {
ret = PTR_ERR(seed_devices);
btrfs_abort_transaction(trans, ret);
goto error_trans;
}
}
mutex_lock(&fs_devices->device_list_mutex);
if (seeding_dev) {
btrfs_setup_sprout(fs_info, seed_devices);
btrfs_assign_next_active_device(fs_info->fs_devices->latest_dev,
device);
}
device->fs_devices = fs_devices;
mutex_lock(&fs_devices->device_list_mutex);
mutex_lock(&fs_info->chunk_mutex);
list_add_rcu(&device->dev_list, &fs_devices->devices);
list_add(&device->dev_alloc_list, &fs_devices->alloc_list);
@ -2744,7 +2777,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
/*
* fs_devices now represents the newly sprouted filesystem and
* its fsid has been changed by btrfs_prepare_sprout
* its fsid has been changed by btrfs_sprout_splice().
*/
btrfs_sysfs_update_sprout_fsid(fs_devices);
}