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Boris Burkov cd1d270e3e btrfs: detect nocow for swap after snapshot delete 
commit a84d5d429f upstream.

can_nocow_extent and btrfs_cross_ref_exist both rely on a heuristic for
detecting a must cow condition which is not exactly accurate, but saves
unnecessary tree traversal. The incorrect assumption is that if the
extent was created in a generation smaller than the last snapshot
generation, it must be referenced by that snapshot. That is true, except
the snapshot could have since been deleted, without affecting the last
snapshot generation.

The original patch claimed a performance win from this check, but it
also leads to a bug where you are unable to use a swapfile if you ever
snapshotted the subvolume it's in. Make the check slower and more strict
for the swapon case, without modifying the general cow checks as a
compromise. Turning swap on does not seem to be a particularly
performance sensitive operation, so incurring a possibly unnecessary
btrfs_search_slot seems worthwhile for the added usability.

Note: Until the snapshot is competely cleaned after deletion,
check_committed_refs will still cause the logic to think that cow is
necessary, so the user must until 'btrfs subvolu sync' finished before
activating the swapfile swapon.

CC: stable@vger.kernel.org # 5.4+
Suggested-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2020-09-03 11:27:02 +02:00
..
tests btrfs: Correctly handle empty trees in find_first_clear_extent_bit 2020-02-11 04:35:34 -08:00
Kconfig btrfs: Fix build error while LIBCRC32C is module 2019-07-17 17:03:30 +02:00
Makefile btrfs: migrate the block group lookup code 2019-09-09 14:59:04 +02:00
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 2020-04-17 10:50:15 +02:00
async-thread.h Btrfs: fix crash during unmount due to race with delayed inode workers 2020-04-17 10:50:15 +02:00
backref.c btrfs: fix double free on ulist after backref resolution failure 2020-07-29 10:18:30 +02:00
backref.h btrfs: fiemap: preallocate ulists for btrfs_check_shared 2019-07-01 13:34:53 +02:00
block-group.c btrfs: add wrapper for transaction abort predicate 2020-08-26 10:40:49 +02:00
block-group.h btrfs: move struct io_ctl to free-space-cache.h 2019-09-09 14:59:15 +02:00
block-rsv.c btrfs: force chunk allocation if our global rsv is larger than metadata 2020-06-22 09:31:13 +02:00
block-rsv.h btrfs: migrate the global_block_rsv helpers to block-rsv.c 2019-07-02 12:30:55 +02:00
btrfs_inode.h btrfs: remove assumption about csum type form btrfs_print_data_csum_error() 2019-07-01 13:35:02 +02:00
check-integrity.c btrfs: fix possible NULL-pointer dereference in integrity checks 2020-02-24 08:36:53 +01:00
check-integrity.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
compression.c btrfs: move cond_wake_up functions out of ctree 2019-09-09 14:59:15 +02:00
compression.h btrfs: compression: replace set_level callbacks by a common helper 2019-09-09 14:59:11 +02:00
ctree.c Btrfs: fix race between adding and putting tree mod seq elements and nodes 2020-02-11 04:35:34 -08:00
ctree.h btrfs: detect nocow for swap after snapshot delete 2020-09-03 11:27:02 +02:00
delalloc-space.c Btrfs: fix qgroup double free after failure to reserve metadata for delalloc 2019-10-17 20:13:44 +02:00
delalloc-space.h btrfs: migrate the delalloc space stuff to it's own home 2019-07-04 17:26:17 +02:00
delayed-inode.c btrfs: add wrapper for transaction abort predicate 2020-08-26 10:40:49 +02:00
delayed-inode.h Btrfs: delayed-inode: use rb_first_cached for ins_root and del_root 2018-10-15 17:23:33 +02:00
delayed-ref.c Btrfs: fix race between adding and putting tree mod seq elements and nodes 2020-02-11 04:35:34 -08:00
delayed-ref.h btrfs: migrate the delayed refs rsv code 2019-07-04 17:26:17 +02:00
dev-replace.c btrfs: move cond_wake_up functions out of ctree 2019-09-09 14:59:15 +02:00
dev-replace.h btrfs: get fs_info from trans in btrfs_run_dev_replace 2019-04-29 19:02:43 +02:00
dir-item.c btrfs: remove unused parameter fs_info from btrfs_extend_item 2019-04-29 19:02:50 +02:00
disk-io.c btrfs: fix space cache memory leak after transaction abort 2020-09-03 11:27:02 +02:00
disk-io.h btrfs: Make reada_tree_block_flagged private 2019-09-09 14:59:11 +02:00
export.c btrfs: export helpers for subvolume name/id resolution 2020-08-26 10:40:49 +02:00
export.h btrfs: export helpers for subvolume name/id resolution 2020-08-26 10:40:49 +02:00
extent-tree.c btrfs: detect nocow for swap after snapshot delete 2020-09-03 11:27:02 +02:00
extent_io.c btrfs: return EROFS for BTRFS_FS_STATE_ERROR cases 2020-08-26 10:40:49 +02:00
extent_io.h btrfs: Remove delalloc_end argument from extent_clear_unlock_delalloc 2019-09-09 14:58:59 +02:00
extent_map.c Btrfs: fix race between using extent maps and merging them 2020-02-19 19:53:00 +01:00
extent_map.h btrfs: Remove impossible condition from mergable_maps 2019-02-25 14:13:21 +01:00
file-item.c btrfs: do not ignore error from btrfs_next_leaf() when inserting checksums 2020-06-22 09:30:55 +02:00
file.c btrfs: detect nocow for swap after snapshot delete 2020-09-03 11:27:02 +02:00
free-space-cache.c btrfs: fix space cache memory leak after transaction abort 2020-09-03 11:27:02 +02:00
free-space-cache.h btrfs: move struct io_ctl to free-space-cache.h 2019-09-09 14:59:15 +02:00
free-space-tree.c btrfs: move basic block_group definitions to their own header 2019-09-09 14:59:03 +02:00
free-space-tree.h btrfs: move basic block_group definitions to their own header 2019-09-09 14:59:03 +02:00
inode-item.c btrfs: Make btrfs_find_name_in_ext_backref return struct btrfs_inode_extref 2019-09-09 14:59:16 +02:00
inode-map.c btrfs: qgroup: Always free PREALLOC META reserve in btrfs_delalloc_release_extents() 2019-10-15 18:50:07 +02:00
inode-map.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
inode.c btrfs: detect nocow for swap after snapshot delete 2020-09-03 11:27:02 +02:00
ioctl.c btrfs: add missing check for nocow and compression inode flags 2020-08-21 13:05:22 +02:00
locking.c btrfs: move cond_wake_up functions out of ctree 2019-09-09 14:59:15 +02:00
locking.h btrfs: Remove unused locking functions 2019-09-09 14:58:59 +02:00
lzo.c btrfs: compression: replace set_level callbacks by a common helper 2019-09-09 14:59:11 +02:00
misc.h btrfs: move math functions to misc.h 2019-09-09 14:59:15 +02:00
ordered-data.c Btrfs: fix btrfs_wait_ordered_range() so that it waits for all ordered extents 2020-02-28 17:22:24 +01:00
ordered-data.h btrfs: don't assume ordered sums to be 4 bytes 2019-07-01 13:35:00 +02:00
orphan.c btrfs: replace GPL boilerplate by SPDX -- sources 2018-04-12 16:29:51 +02:00
print-tree.c btrfs: switch extent_buffer write_locks from atomic to int 2019-07-02 12:30:47 +02:00
print-tree.h btrfs: print-tree: debugging output enhancement 2018-04-20 19:18:16 +02:00
props.c btrfs: rename the btrfs_calc_*_metadata_size helpers 2019-09-09 14:59:13 +02:00
props.h btrfs: delete unused function btrfs_set_prop_trans 2019-04-29 19:02:54 +02:00
qgroup.c btrfs: make btrfs_qgroup_check_reserved_leak take btrfs_inode 2020-09-03 11:26:47 +02:00
qgroup.h btrfs: make btrfs_qgroup_check_reserved_leak take btrfs_inode 2020-09-03 11:26:47 +02:00
raid56.c btrfs: get rid of unique workqueue helper functions 2020-01-09 10:20:06 +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: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
reada.c btrfs: get rid of unique workqueue helper functions 2020-01-09 10:20:06 +01:00
ref-verify.c btrfs: ref-verify: fix memory leak in add_block_entry 2020-08-21 13:05:21 +02:00
ref-verify.h btrfs: ref-verify: Use btrfs_ref to refactor btrfs_ref_tree_mod() 2019-04-29 19:02:49 +02:00
relocation.c btrfs: relocation: review the call sites which can be interrupted by signal 2020-08-21 13:05:22 +02:00
root-tree.c btrfs: do not delete mismatched root refs 2020-01-23 08:22:40 +01:00
scrub.c btrfs: return EROFS for BTRFS_FS_STATE_ERROR cases 2020-08-26 10:40:49 +02:00
send.c btrfs: send: emit file capabilities after chown 2020-06-22 09:31:12 +02:00
send.h btrfs: replace GPL boilerplate by SPDX -- headers 2018-04-12 16:29:46 +02:00
space-info.c btrfs: fix lockdep splat from btrfs_dump_space_info 2020-08-19 08:16:01 +02:00
space-info.h btrfs: improve global reserve stealing logic 2020-06-22 09:31:08 +02:00
struct-funcs.c btrfs: tie extent buffer and it's token together 2019-09-09 14:59:16 +02:00
super.c btrfs: reset compression level for lzo on remount 2020-09-03 11:27:02 +02:00
sysfs.c btrfs: sysfs: use NOFS for device creation 2020-08-21 13:05:22 +02:00
sysfs.h btrfs: sysfs: move helper macros to sysfs.c 2019-09-09 14:59:08 +02:00
transaction.c btrfs: add wrapper for transaction abort predicate 2020-08-26 10:40:49 +02:00
transaction.h btrfs: add wrapper for transaction abort predicate 2020-08-26 10:40:49 +02:00
tree-checker.c Btrfs: make tree checker detect checksum items with overlapping ranges 2019-12-31 16:41:55 +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: open code now trivial btrfs_set_lock_blocking 2019-02-25 14:13:27 +01:00
tree-log.c btrfs: check the right error variable in btrfs_del_dir_entries_in_log 2020-09-03 11:27:02 +02:00
tree-log.h btrfs: get fs_info from trans in btrfs_set_log_full_commit 2019-04-29 19:02:41 +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: handle ENOENT in btrfs_uuid_tree_iterate 2019-12-31 16:42:05 +01:00
volumes.c btrfs: relocation: review the call sites which can be interrupted by signal 2020-08-21 13:05:22 +02:00
volumes.h btrfs: Remove btrfs_bio::flags member 2019-12-17 19:56:06 +01:00
xattr.c Btrfs: fix failure to persist compression property xattr deletion on fsync 2019-06-17 16:37:17 +02:00
xattr.h btrfs: cleanup btrfs_setxattr_trans and drop transaction parameter 2019-04-29 19:02:44 +02:00
zlib.c btrfs: compression: replace set_level callbacks by a common helper 2019-09-09 14:59:11 +02:00
zstd.c btrfs: move cond_wake_up functions out of ctree 2019-09-09 14:59:15 +02:00