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linux/fs/btrfs
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David Sterba dccdb07bc9 btrfs: kill btrfs_fs_info::volume_mutex 
Mutual exclusion of device add/rm and balance was done by the volume
mutex up to version 3.7. The commit 5ac00addc7 ("Btrfs: disallow
mutually exclusive admin operations from user mode") added a bit that
essentially tracked the same information.

The status bit has an advantage over a mutex that it can be set without
restrictions of function context, so it started to be used in the
mount-time resuming of balance or device replace.

But we don't really need to track the same information in two ways.

1) After the previous cleanups, the main ioctl handlers for
   add/del/resize copy the EXCL_OP bit next to the volume mutex, here
   it's clearly safe.

2) Resuming balance during mount or after rw remount will set only the
   EXCL_OP bit and the volume_mutex is held in the kernel thread that
   calls btrfs_balance.

3) Resuming device replace during mount or after rw remount is done
   after balance and is excluded by the EXCL_OP bit. It does not take
   the volume_mutex at all and completely relies on the EXCL_OP bit.

4) The resuming of balance and dev-replace cannot hapen at the same time
   as the ioctls cannot be started in parallel. Nevertheless, a crafted
   image could trigger that and a warning is printed.

5) Balance is normally excluded by EXCL_OP and also uses own mutex to
   protect against concurrent access to its status data. There's some
   trickery to maintain the right lock nesting in case we need to
   reexamine the status in btrfs_ioctl_balance. The volume_mutex is
   removed and the unlock/lock sequence is left in place as we might
   expect other waiters to proceed.

6) Similar to 5, the unlock/lock sequence is kept in
   btrfs_cancel_balance to allow waiters to continue.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2018-05-28 18:07:25 +02:00
..
tests btrfs: use fs_info for btrfs_handle_em_exist tracepoint 2018-05-28 18:07:17 +02:00
acl.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
async-thread.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
async-thread.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
backref.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
backref.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
btrfs_inode.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
check-integrity.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
check-integrity.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
compression.c for-4.17-part2-tag 2018-04-15 18:08:35 -07:00
compression.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
ctree.c btrfs: fix reading stale metadata blocks after degraded raid1 mounts 2018-05-17 14:18:25 +02:00
ctree.h btrfs: kill btrfs_fs_info::volume_mutex 2018-05-28 18:07:25 +02:00
dedupe.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
delayed-inode.c btrfs: delayed-inode: Remove wrong qgroup meta reservation calls 2018-04-18 16:46:55 +02:00
delayed-inode.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
delayed-ref.c btrfs: Drop fs_info parameter from btrfs_merge_delayed_refs 2018-05-28 18:07:20 +02:00
delayed-ref.h btrfs: Drop fs_info parameter from btrfs_merge_delayed_refs 2018-05-28 18:07:20 +02:00
dev-replace.c btrfs: remove wrong use of volume_mutex from btrfs_dev_replace_start 2018-05-28 18:07:25 +02:00
dev-replace.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
dir-item.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
disk-io.c btrfs: kill btrfs_fs_info::volume_mutex 2018-05-28 18:07:25 +02:00
disk-io.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
export.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
export.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
extent-tree.c btrfs: kill btrfs_fs_info::volume_mutex 2018-05-28 18:07:25 +02:00
extent_io.c btrfs: Remove tree argument from extent_writepages 2018-05-28 18:07:20 +02:00
extent_io.h btrfs: Remove tree argument from extent_writepages 2018-05-28 18:07:20 +02:00
extent_map.c btrfs: use fs_info for btrfs_handle_em_exist tracepoint 2018-05-28 18:07:17 +02:00
extent_map.h btrfs: use fs_info for btrfs_handle_em_exist tracepoint 2018-05-28 18:07:17 +02:00
file-item.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
file.c btrfs: Fix wrong btrfs_delalloc_release_extents parameter 2018-04-18 16:46:57 +02:00
free-space-cache.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
free-space-cache.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
free-space-tree.c btrfs: optimize free space tree bitmap conversion 2018-05-28 18:07:18 +02:00
free-space-tree.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
inode-item.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
inode-map.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
inode-map.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
inode.c btrfs: Remove btrfs_wait_and_free_delalloc_work 2018-05-28 18:07:20 +02:00
ioctl.c btrfs: kill btrfs_fs_info::volume_mutex 2018-05-28 18:07:25 +02:00
Kconfig btrfs: add SPDX header to Kconfig 2018-04-12 16:29:55 +02:00
locking.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
locking.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
lzo.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
Makefile btrfs: Remove custom crc32c init code 2018-03-26 15:09:39 +02:00
math.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
ordered-data.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
ordered-data.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
orphan.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
print-tree.c btrfs: print-tree: debugging output enhancement 2018-04-20 19:18:16 +02:00
print-tree.h btrfs: print-tree: debugging output enhancement 2018-04-20 19:18:16 +02:00
props.c btrfs: property: Set incompat flag if lzo/zstd compression is set 2018-05-17 14:18:25 +02:00
props.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
qgroup.c btrfs: qgroup: Commit transaction in advance to reduce early EDQUOT 2018-04-18 16:46:47 +02:00
qgroup.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
raid56.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
raid56.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
rcu-string.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
reada.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
ref-verify.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
ref-verify.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
relocation.c btrfs: Fix wrong first_key parameter in replace_path 2018-04-26 13:21:04 +02:00
root-tree.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
scrub.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
send.c Btrfs: send, fix missing truncate for inode with prealloc extent past eof 2018-05-02 11:55:29 +02:00
send.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
struct-funcs.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
super.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
sysfs.c btrfs: rename struct btrfs_fs_devices::list 2018-05-28 18:07:21 +02:00
sysfs.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
transaction.c btrfs: qgroup: Commit transaction in advance to reduce early EDQUOT 2018-04-18 16:46:47 +02:00
transaction.h btrfs: qgroup: Commit transaction in advance to reduce early EDQUOT 2018-04-18 16:46:47 +02:00
tree-checker.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
tree-checker.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
tree-defrag.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
tree-log.c Btrfs: fix duplicate extents after fsync of file with prealloc extents 2018-05-17 14:18:19 +02:00
tree-log.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
ulist.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
ulist.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
uuid-tree.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
volumes.c btrfs: kill btrfs_fs_info::volume_mutex 2018-05-28 18:07:25 +02:00
volumes.h btrfs: move btrfs_init_dev_replace_tgtdev to dev-replace.c and make static 2018-05-28 18:07:24 +02:00
xattr.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
xattr.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
zlib.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
zstd.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00