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linux/fs/btrfs
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Filipe Manana dd0734f2a8 btrfs: fix race between swap file activation and snapshot creation 
When creating a snapshot we check if the current number of swap files, in
the root, is non-zero, and if it is, we error out and warn that we can not
create the snapshot because there are active swap files.

However this is racy because when a task started activation of a swap
file, another task might have started already snapshot creation and might
have seen the counter for the number of swap files as zero. This means
that after the swap file is activated we may end up with a snapshot of the
same root successfully created, and therefore when the first write to the
swap file happens it has to fall back into COW mode, which should never
happen for active swap files.

Basically what can happen is:

1) Task A starts snapshot creation and enters ioctl.c:create_snapshot().
   There it sees that root->nr_swapfiles has a value of 0 so it continues;

2) Task B enters btrfs_swap_activate(). It is not aware that another task
   started snapshot creation but it did not finish yet. It increments
   root->nr_swapfiles from 0 to 1;

3) Task B checks that the file meets all requirements to be an active
   swap file - it has NOCOW set, there are no snapshots for the inode's
   root at the moment, no file holes, no reflinked extents, etc;

4) Task B returns success and now the file is an active swap file;

5) Task A commits the transaction to create the snapshot and finishes.
   The swap file's extents are now shared between the original root and
   the snapshot;

6) A write into an extent of the swap file is attempted - there is a
   snapshot of the file's root, so we fall back to COW mode and therefore
   the physical location of the extent changes on disk.

So fix this by taking the snapshot lock during swap file activation before
locking the extent range, as that is the order in which we lock these
during buffered writes.

Fixes: ed46ff3d42 ("Btrfs: support swap files")
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-02-22 18:07:35 +01:00
..
tests btrfs: extend btrfs_rmap_block for specifying a device 2021-02-09 02:46:05 +01:00
acl.c btrfs: cleanup btrfs_setxattr_trans and drop transaction parameter 2019-04-29 19:02:44 +02:00
async-thread.c Btrfs: fix crash during unmount due to race with delayed inode workers 2020-03-23 17:01:51 +01:00
async-thread.h Btrfs: fix crash during unmount due to race with delayed inode workers 2020-03-23 17:01:51 +01:00
backref.c btrfs: do not warn if we can't find the reloc root when looking up backref 2021-02-08 22:58:56 +01:00
backref.h btrfs: add asserts for deleting backref cache nodes 2021-02-08 22:58:56 +01:00
block-group.c btrfs: fix race between writes to swap files and scrub 2021-02-22 18:07:15 +01:00
block-group.h btrfs: fix race between writes to swap files and scrub 2021-02-22 18:07:15 +01:00
block-rsv.c btrfs: introduce mount option rescue=ignorebadroots 2020-12-08 15:53:41 +01:00
block-rsv.h btrfs: Remove __ prefix from btrfs_block_rsv_release 2020-03-23 17:01:55 +01:00
btrfs_inode.h btrfs: make btrfs_dio_private::bytes u32 2021-02-08 22:58:51 +01:00
check-integrity.c btrfs: drop casts of bio bi_sector 2020-12-09 19:16:05 +01:00
check-integrity.h btrfs: remove btrfsic_submit_bh() 2020-03-23 17:01:39 +01:00
compression.c btrfs: make check_compressed_csum() to be subpage compatible 2021-02-22 17:15:27 +01:00
compression.h btrfs: compression: move declarations to header 2020-10-07 12:06:55 +02:00
ctree.c btrfs: fix extent buffer leak on failure to copy root 2021-02-08 22:59:04 +01:00
ctree.h btrfs: fix race between writes to swap files and scrub 2021-02-22 18:07:15 +01:00
delalloc-space.c btrfs: fix parameter description of btrfs_inode_rsv_release/btrfs_delalloc_release_space 2021-02-08 22:58:54 +01:00
delalloc-space.h btrfs: make btrfs_delalloc_reserve_space take btrfs_inode 2020-07-27 12:55:36 +02:00
delayed-inode.c btrfs: simplify condition in __btrfs_run_delayed_items 2021-02-08 22:58:59 +01:00
delayed-inode.h btrfs: make btrfs_delayed_update_inode take btrfs_inode 2020-12-08 15:54:10 +01:00
delayed-ref.c btrfs: account for new extents being deleted in total_bytes_pinned 2021-02-08 22:58:55 +01:00
delayed-ref.h btrfs: only let one thread pre-flush delayed refs in commit 2021-02-08 22:58:56 +01:00
dev-replace.c btrfs: zoned: mark block groups to copy for device-replace 2021-02-09 02:46:07 +01:00
dev-replace.h btrfs: zoned: mark block groups to copy for device-replace 2021-02-09 02:46:07 +01:00
dir-item.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
discard.c btrfs: document now parameter of peek_discard_list 2021-02-08 22:58:53 +01:00
discard.h btrfs: cleanup btrfs_discard_update_discardable usage 2020-12-08 15:54:02 +01:00
disk-io.c btrfs: zoned: reorder log node allocation on zoned filesystem 2021-02-09 02:48:41 +01:00
disk-io.h btrfs: split alloc_log_tree() 2021-02-09 02:46:07 +01:00
export.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
export.h btrfs: export helpers for subvolume name/id resolution 2020-03-23 17:01:42 +01:00
extent-io-tree.h btrfs: use fixed width int type for extent_state::state 2020-12-08 15:54:13 +01:00
extent-tree.c btrfs: zoned: extend zoned allocator to use dedicated tree-log block group 2021-02-09 02:46:08 +01:00
extent_io.c btrfs: zoned: relocate block group to repair IO failure in zoned filesystems 2021-02-09 02:46:07 +01:00
extent_io.h btrfs: zoned: redirty released extent buffers 2021-02-09 02:46:04 +01:00
extent_map.c btrfs: fix parameter description of btrfs_add_extent_mapping 2021-02-08 22:58:53 +01:00
extent_map.h btrfs: remove extent_map::bdev 2019-11-18 23:43:44 +01:00
file-item.c btrfs: fix function description formats in file-item.c 2021-02-08 22:58:53 +01:00
file.c btrfs: zoned: use ZONE_APPEND write for zoned mode 2021-02-09 02:46:06 +01:00
free-space-cache.c btrfs: fix race between extent freeing/allocation when using bitmaps 2021-02-22 17:15:31 +01:00
free-space-cache.h btrfs: zoned: track unusable bytes for zones 2021-02-09 02:46:03 +01:00
free-space-tree.c btrfs: fix possible free space tree corruption with online conversion 2021-01-25 18:44:37 +01:00
free-space-tree.h btrfs: rename btrfs_block_group_cache 2019-11-18 17:51:51 +01:00
inode-item.c btrfs: locking: rip out path->leave_spinning 2020-12-08 15:54:02 +01:00
inode.c btrfs: fix race between swap file activation and snapshot creation 2021-02-22 18:07:35 +01:00
ioctl.c btrfs: zoned: disallow fitrim on zoned filesystems 2021-02-09 02:32:20 +01:00
Kconfig btrfs: switch to iomap for direct IO 2020-10-07 12:06:57 +02:00
locking.c btrfs: remove the recurse parameter from __btrfs_tree_read_lock 2020-12-08 15:54:09 +01:00
locking.h btrfs: remove the recurse parameter from __btrfs_tree_read_lock 2020-12-08 15:54:09 +01:00
lzo.c btrfs: compression: inline free_workspace 2019-11-18 12:46:59 +01:00
Makefile btrfs: introduce the skeleton of btrfs_subpage structure 2021-02-08 22:59:01 +01:00
misc.h btrfs: rename tree_entry to rb_simple_node and export it 2020-05-25 11:25:19 +02:00
ordered-data.c btrfs: zoned: use ZONE_APPEND write for zoned mode 2021-02-09 02:46:06 +01:00
ordered-data.h btrfs: zoned: use ZONE_APPEND write for zoned mode 2021-02-09 02:46:06 +01:00
orphan.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
print-tree.c btrfs: print the actual offset in btrfs_root_name 2021-01-07 17:25:05 +01:00
print-tree.h btrfs: print the actual offset in btrfs_root_name 2021-01-07 17:25:05 +01:00
props.c btrfs: simplify iget helpers 2020-05-25 11:25:37 +02:00
props.h btrfs: delete unused function btrfs_set_prop_trans 2019-04-29 19:02:54 +02:00
qgroup.c btrfs: fix transaction leak and crash after RO remount caused by qgroup rescan 2020-12-18 14:59:57 +01:00
qgroup.h btrfs: qgroup: export qgroups in sysfs 2020-07-27 12:55:37 +02:00
raid56.c btrfs: fix raid6 qstripe kmap 2021-02-22 17:15:21 +01:00
raid56.h btrfs: constify map parameter for nr_parity_stripes and nr_data_stripes 2019-07-01 13:34:58 +02:00
rcu-string.h btrfs: rcu-string: Replace zero-length array with flexible-array member 2020-03-23 17:01:53 +01:00
reada.c btrfs: pass the owner_root and level to alloc_extent_buffer 2020-12-08 15:54:07 +01:00
ref-verify.c btrfs: ref-verify: make sure owner is set for all refs 2021-02-08 22:58:50 +01:00
ref-verify.h btrfs: ref-verify: Use btrfs_ref to refactor btrfs_ref_tree_mod() 2019-04-29 19:02:49 +02:00
reflink.c btrfs: introduce btrfs_subpage for data inodes 2021-02-08 22:59:03 +01:00
reflink.h Btrfs: move all reflink implementation code into its own file 2020-03-23 17:01:54 +01:00
relocation.c btrfs: zoned: enable relocation on a zoned filesystem 2021-02-09 02:46:07 +01:00
root-tree.c btrfs: qgroup: fix qgroup meta rsv leak for subvolume operations 2020-10-07 12:12:13 +02:00
scrub.c btrfs: fix race between writes to swap files and scrub 2021-02-22 18:07:15 +01:00
send.c btrfs: send: use struct send_ctx *sctx for btrfs_compare_trees and changed_cb 2021-02-08 22:58:57 +01:00
send.h btrfs: send: avoid copying file data 2020-10-07 12:13:17 +02:00
space-info.c btrfs: zoned: track unusable bytes for zones 2021-02-09 02:46:03 +01:00
space-info.h btrfs: zoned: track unusable bytes for zones 2021-02-09 02:46:03 +01:00
struct-funcs.c btrfs: handle sectorsize < PAGE_SIZE case for extent buffer accessors 2020-12-09 19:16:10 +01:00
subpage.c btrfs: integrate page status update for data read path into begin/end_page_read 2021-02-08 22:59:03 +01:00
subpage.h btrfs: integrate page status update for data read path into begin/end_page_read 2021-02-08 22:59:03 +01:00
super.c btrfs: allow read-only mount of 4K sector size fs on 64K page system 2021-02-08 22:59:03 +01:00
sysfs.c btrfs: zoned: track unusable bytes for zones 2021-02-09 02:46:03 +01:00
sysfs.h btrfs: split and refactor btrfs_sysfs_remove_devices_dir 2020-10-07 12:12:21 +02:00
transaction.c btrfs: zoned: redirty released extent buffers 2021-02-09 02:46:04 +01:00
transaction.h btrfs: zoned: redirty released extent buffers 2021-02-09 02:46:04 +01:00
tree-checker.c btrfs: tree-checker: check if chunk item end overflows 2021-01-07 17:25:05 +01:00
tree-checker.h btrfs: get fs_info from eb in btrfs_check_chunk_valid 2019-04-29 19:02:39 +02:00
tree-defrag.c btrfs: locking: remove all the blocking helpers 2020-12-08 15:54:01 +01:00
tree-log.c btrfs: zoned: deal with holes writing out tree-log pages 2021-02-09 02:52:24 +01:00
tree-log.h btrfs: make fast fsyncs wait only for writeback 2020-10-07 12:06:56 +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: remove unnecessary casts in printk 2020-12-08 15:53:52 +01:00
volumes.c btrfs: zoned: relocate block group to repair IO failure in zoned filesystems 2021-02-09 02:46:07 +01:00
volumes.h btrfs: zoned: relocate block group to repair IO failure in zoned filesystems 2021-02-09 02:46:07 +01:00
xattr.c btrfs: skip unnecessary searches for xattrs when logging an inode 2020-12-08 15:54:12 +01:00
xattr.h btrfs: cleanup btrfs_setxattr_trans and drop transaction parameter 2019-04-29 19:02:44 +02:00
zlib.c btrfs: use larger zlib buffer for s390 hardware compression 2020-01-31 10:30:40 -08:00
zoned.c btrfs: zoned: support dev-replace in zoned filesystems 2021-02-09 02:46:07 +01:00
zoned.h btrfs: zoned: extend zoned allocator to use dedicated tree-log block group 2021-02-09 02:46:08 +01:00
zstd.c btrfs: compression: inline free_workspace 2019-11-18 12:46:59 +01:00