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btrfs: protect exclusive_operation by super_lock 

The exclusive operation is now atomically checked and set using bit
operations. Switch it to protection by spinlock. The super block lock is
not frequently used and adding a new lock seems like an overkill so it
should be safe to reuse it.

The reason to use spinlock is to enhance the locking context so more
checks can be done, eg. allowing the same exclusive operation enter
the exclop section and cancel the running one. This will be used for
resize and device delete.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2021-05-14 17:42:30 +02:00
parent 24880be59c
commit 0d7ed32c1e
2 changed files with 17 additions and 3 deletions
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4
fs/btrfs/ctree.h
View File

@ -992,8 +992,8 @@ struct btrfs_fs_info {
*/ */
int send_in_progress; int send_in_progress;
/* Type of exclusive operation running */ /* Type of exclusive operation running, protected by super_lock */
unsigned long exclusive_operation; enum btrfs_exclusive_operation exclusive_operation;
/* /*
* Zone size > 0 when in ZONED mode, otherwise it's used for a check * Zone size > 0 when in ZONED mode, otherwise it's used for a check

16
fs/btrfs/ioctl.c
View File

@ -353,15 +353,29 @@ update_flags:
return ret; return ret;
} }
/*
* Start exclusive operation @type, return true on success
*/
bool btrfs_exclop_start(struct btrfs_fs_info *fs_info, bool btrfs_exclop_start(struct btrfs_fs_info *fs_info,
enum btrfs_exclusive_operation type) enum btrfs_exclusive_operation type)
{ {
return !cmpxchg(&fs_info->exclusive_operation, BTRFS_EXCLOP_NONE, type); bool ret = false;
spin_lock(&fs_info->super_lock);
if (fs_info->exclusive_operation == BTRFS_EXCLOP_NONE) {
fs_info->exclusive_operation = type;
ret = true;
}
spin_unlock(&fs_info->super_lock);
return ret;
} }
void btrfs_exclop_finish(struct btrfs_fs_info *fs_info) void btrfs_exclop_finish(struct btrfs_fs_info *fs_info)
{ {
spin_lock(&fs_info->super_lock);
WRITE_ONCE(fs_info->exclusive_operation, BTRFS_EXCLOP_NONE); WRITE_ONCE(fs_info->exclusive_operation, BTRFS_EXCLOP_NONE);
spin_unlock(&fs_info->super_lock);
sysfs_notify(&fs_info->fs_devices->fsid_kobj, NULL, "exclusive_operation"); sysfs_notify(&fs_info->fs_devices->fsid_kobj, NULL, "exclusive_operation");
} }