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alistair23-linux/fs/btrfs
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Nikolay Borisov 6ef108dd0c btrfs: Streamline btrfs_fs_info::backup_root_index semantics 
The backup_root_index member stores the index at which the backup root
should be saved upon next transaction commit. However, there is a
small deviation from this behavior in the form of a check in
backup_super_roots which checks if current root generation equals to the
generation of the previous root. This can trigger in the following
scenario:

slot0: gen-2
slot1: gen-1
slot2: gen
slot3: unused

Now suppose slot3 (which is also the root specified in the super block)
is corrupted hence init_tree_roots chooses to use the backup root at
slot2, meaning read_backup_root will read slot2 and assign the
superblock generation to gen-1. Despite this backup_root_index will
point at slot3 because its init happens in init_backup_root_slot, long
before any parsing of the backup roots occur. Then on next transaction
start, gen-1 will be incremented by 1 making the root's generation
equal gen. Subsequently, on transaction commit the following check
triggers:

  if (btrfs_backup_tree_root_gen(root_backup) ==
           btrfs_header_generation(info->tree_root->node))

This causes the 'next_backup', which is the index at which the backup is
going to be written to, to set to last_backup, which will be slot2.

All of this is a very confusing way of expressing the following
invariant:

 Always write a backup root at the index following the last used backup
 root.

This commit streamlines this logic by setting backup_root_index to the
next index after the one used for mount.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2019-11-18 17:51:47 +01:00
..
tests btrfs: add dedicated members for start and length of a block group 2019-11-18 17:51:45 +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: add __pure attribute to functions 2019-11-18 12:46:52 +01:00
async-thread.h btrfs: add __pure attribute to functions 2019-11-18 12:46:52 +01:00
backref.c Btrfs: fix deadlock between fiemap and transaction commits 2019-07-30 18:25:12 +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 dedicated members for start and length of a block group 2019-11-18 17:51:45 +01:00
block-group.h btrfs: add dedicated members for start and length of a block group 2019-11-18 17:51:45 +01:00
block-rsv.c btrfs: use btrfs_try_granting_tickets in update_global_rsv 2019-09-09 14:59:19 +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 unnecessary delalloc mutex for inodes 2019-11-18 17:51:46 +01:00
check-integrity.c btrfs: reduce stack usage for btrfsic_process_written_block 2019-09-09 14:58:58 +02:00
check-integrity.h
compression.c btrfs: compression: remove ops pointer from workspace_manager 2019-11-18 12:46:59 +01:00
compression.h btrfs: compression: remove ops pointer from workspace_manager 2019-11-18 12:46:59 +01:00
ctree.c btrfs: add blake2b to checksumming algorithms 2019-11-18 17:51:44 +01:00
ctree.h btrfs: rename extent buffer block group item accessors 2019-11-18 17:51:45 +01:00
delalloc-space.c Btrfs: remove unnecessary delalloc mutex for inodes 2019-11-18 17:51:46 +01:00
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: use refcount_inc_not_zero in kill_all_nodes 2019-11-18 12:46:51 +01:00
delayed-inode.h
delayed-ref.c btrfs: rename btrfs_space_info_add_old_bytes 2019-09-09 14:59:18 +02:00
delayed-ref.h btrfs: migrate the delayed refs rsv code 2019-07-04 17:26:17 +02:00
dev-replace.c btrfs: add __pure attribute to functions 2019-11-18 12:46:52 +01:00
dev-replace.h btrfs: add __pure attribute to functions 2019-11-18 12:46:52 +01:00
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: Streamline btrfs_fs_info::backup_root_index semantics 2019-11-18 17:51:47 +01:00
disk-io.h btrfs: add __cold attribute to more functions 2019-11-18 12:46:52 +01:00
export.c btrfs: drop unused parameter is_new from btrfs_iget 2019-11-18 12:46:52 +01:00
export.h
extent-io-tree.h btrfs: move the failrec tree stuff into extent-io-tree.h 2019-11-18 12:46:47 +01:00
extent-tree.c btrfs: add dedicated members for start and length of a block group 2019-11-18 17:51:45 +01:00
extent_io.c btrfs: Avoid getting stuck during cyclic writebacks 2019-11-18 12:46:54 +01:00
extent_io.h btrfs: opencode extent_buffer_get 2019-11-18 12:46:54 +01:00
extent_map.c btrfs: assert extent_map bdevs and lookup_map and split 2019-11-18 12:47:01 +01:00
extent_map.h btrfs: assert extent_map bdevs and lookup_map and split 2019-11-18 12:47:01 +01:00
file-item.c btrfs: directly call into crypto framework for checksumming 2019-07-01 13:35:02 +02:00
file.c btrfs: Return offset from find_desired_extent 2019-11-18 12:47:00 +01:00
free-space-cache.c btrfs: add dedicated members for start and length of a block group 2019-11-18 17:51:45 +01:00
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: add dedicated members for start and length of a block group 2019-11-18 17:51:45 +01:00
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
inode.c Btrfs: remove unnecessary delalloc mutex for inodes 2019-11-18 17:51:46 +01:00
ioctl.c btrfs: add dedicated members for start and length of a block group 2019-11-18 17:51:45 +01:00
Kconfig btrfs: add sha256 to checksumming algorithm 2019-11-18 17:51:43 +01:00
locking.c btrfs: move btrfs_unlock_up_safe to other locking functions 2019-11-18 12:46:49 +01:00
locking.h btrfs: move btrfs_unlock_up_safe to other locking functions 2019-11-18 12:46:49 +01:00
lzo.c btrfs: compression: inline free_workspace 2019-11-18 12:46:59 +01:00
Makefile btrfs: migrate the block group lookup code 2019-09-09 14:59:04 +02:00
misc.h btrfs: add 64bit safe helper for power of two checks 2019-11-18 12:46:50 +01:00
ordered-data.c btrfs: get rid of unique workqueue helper functions 2019-11-18 12:46:48 +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
print-tree.c btrfs: rename extent buffer block group item accessors 2019-11-18 17:51:45 +01:00
print-tree.h
props.c btrfs: props: remove unnecessary hash_init() 2019-11-18 12:46:55 +01:00
props.h btrfs: delete unused function btrfs_set_prop_trans 2019-04-29 19:02:54 +02:00
qgroup.c btrfs: opencode extent_buffer_get 2019-11-18 12:46:54 +01:00
qgroup.h btrfs: qgroup: Move reserved data accounting from btrfs_delayed_ref_head to btrfs_qgroup_extent_record 2019-02-25 14:13:39 +01:00
raid56.c btrfs: remove pointless local variable in lock_stripe_add() 2019-11-18 12:47:00 +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
reada.c btrfs: add dedicated members for start and length of a block group 2019-11-18 17:51:45 +01:00
ref-verify.c btrfs: fix uninitialized ret in ref-verify 2019-10-03 15:00:56 +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: add dedicated members for start and length of a block group 2019-11-18 17:51:45 +01:00
root-tree.c btrfs: rename the btrfs_calc_*_metadata_size helpers 2019-09-09 14:59:13 +02:00
scrub.c btrfs: add dedicated members for start and length of a block group 2019-11-18 17:51:45 +01:00
send.c btrfs: drop unused parameter is_new from btrfs_iget 2019-11-18 12:46:52 +01:00
send.h
space-info.c Btrfs: remove wait queue from space_info structure 2019-11-18 17:51:46 +01:00
space-info.h Btrfs: remove wait queue from space_info structure 2019-11-18 17:51:46 +01:00
struct-funcs.c btrfs: tie extent buffer and it's token together 2019-09-09 14:59:16 +02:00
super.c btrfs: remove cached space_info in btrfs_statfs() 2019-11-18 17:51:45 +01:00
sysfs.c btrfs: add dedicated members for start and length of a block group 2019-11-18 17:51:45 +01:00
sysfs.h btrfs: sysfs: move helper macros to sysfs.c 2019-09-09 14:59:08 +02:00
transaction.c btrfs: Rename btrfs_join_transaction_nolock 2019-11-18 12:46:54 +01:00
transaction.h btrfs: Rename btrfs_join_transaction_nolock 2019-11-18 12:46:54 +01:00
tree-checker.c btrfs: rename block_group_item on-stack accessors to follow naming 2019-11-18 17:51:45 +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: opencode extent_buffer_get 2019-11-18 12:46:54 +01:00
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
ulist.h
uuid-tree.c btrfs: remove unused parameter fs_info from btrfs_extend_item 2019-04-29 19:02:50 +02:00
volumes.c btrfs: add dedicated members for start and length of a block group 2019-11-18 17:51:45 +01:00
volumes.h btrfs: Remove btrfs_bio::flags member 2019-11-18 17:51:44 +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: inline free_workspace 2019-11-18 12:46:59 +01:00
zstd.c btrfs: compression: inline free_workspace 2019-11-18 12:46:59 +01:00