From 0d7ed32c1eebfa34e28d24930ea598a4492d289e Mon Sep 17 00:00:00 2001 From: David Sterba Date: Fri, 14 May 2021 17:42:30 +0200 Subject: [PATCH] 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 Signed-off-by: David Sterba --- fs/btrfs/ctree.h | 4 ++-- fs/btrfs/ioctl.c | 16 +++++++++++++++- 2 files changed, 17 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index a3b628ea4d64..4049f533e35e 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -992,8 +992,8 @@ struct btrfs_fs_info { */ int send_in_progress; - /* Type of exclusive operation running */ - unsigned long exclusive_operation; + /* Type of exclusive operation running, protected by super_lock */ + enum btrfs_exclusive_operation exclusive_operation; /* * Zone size > 0 when in ZONED mode, otherwise it's used for a check diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index a7739461533d..c4e710ea08ba 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -353,15 +353,29 @@ update_flags: return ret; } +/* + * Start exclusive operation @type, return true on success + */ bool btrfs_exclop_start(struct btrfs_fs_info *fs_info, 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) { + spin_lock(&fs_info->super_lock); 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"); }