linux.git/fs/btrfs/compression.c, branch v5.11

btrfs: refactor btrfs_lookup_bio_sums to handle out-of-order bvecs

2020-12-09T18:16:11+00:00

Refactor btrfs_lookup_bio_sums() by:

- Remove the @file_offset parameter
  There are two factors making the @file_offset parameter useless:

  * For csum lookup in csum tree, file offset makes no sense
    We only need disk_bytenr, which is unrelated to file_offset

  * page_offset (file offset) of each bvec is not contiguous.
    Pages can be added to the same bio as long as their on-disk bytenr
    is contiguous, meaning we could have pages at different file offsets
    in the same bio.

  Thus passing file_offset makes no sense any more.
  The only user of file_offset is for data reloc inode, we will use
  a new function, search_file_offset_in_bio(), to handle it.

- Extract the csum tree lookup into search_csum_tree()
  The new function will handle the csum search in csum tree.
  The return value is the same as btrfs_find_ordered_sum(), returning
  the number of found sectors which have checksum.

- Change how we do the main loop
  The only needed info from bio is:
  * the on-disk bytenr
  * the length

  After extracting the above info, we can do the search without bio
  at all, which makes the main loop much simpler:

	for (cur_disk_bytenr = orig_disk_bytenr;
	     cur_disk_bytenr < orig_disk_bytenr + orig_len;
	     cur_disk_bytenr += count * sectorsize) {

		/* Lookup csum tree */
		count = search_csum_tree(fs_info, path, cur_disk_bytenr,
					 search_len, csum_dst);
		if (!count) {
			/* Csum hole handling */
		}
	}

- Use single variable as the source to calculate all other offsets
  Instead of all different type of variables, we use only one main
  variable, cur_disk_bytenr, which represents the current disk bytenr.

  All involved values can be calculated from that variable, and
  all those variable will only be visible in the inner loop.

The above refactoring makes btrfs_lookup_bio_sums() way more robust than
it used to be, especially related to the file offset lookup.  Now
file_offset lookup is only related to data reloc inode, otherwise we
don't need to bother file_offset at all.

Signed-off-by: Qu Wenruo 
Signed-off-by: David Sterba

btrfs: drop casts of bio bi_sector

2020-12-09T18:16:05+00:00

Since commit 72deb455b5ec ("block: remove CONFIG_LBDAF") (5.2) the
sector_t type is u64 on all arches and configs so we don't need to
typecast it.  It used to be unsigned long and the result of sector size
shifts were not guaranteed to fit in the type.

Reviewed-by: Johannes Thumshirn 
Signed-off-by: David Sterba

btrfs: remove unnecessary local variables for checksum size

2020-12-08T14:54:00+00:00

Remove local variable that is then used just once and replace it with
fs_info::csum_size.

Reviewed-by: Johannes Thumshirn 
Signed-off-by: David Sterba

btrfs: switch cached fs_info::csum_size from u16 to u32

2020-12-08T14:53:59+00:00

The fs_info value is 32bit, switch also the local u16 variables. This
leads to a better assembly code generated due to movzwl.

This simple change will shave some bytes on x86_64 and release config:

   text    data     bss     dec     hex filename
1090000   17980   14912 1122892  11224c pre/btrfs.ko
1089794   17980   14912 1122686  11217e post/btrfs.ko

DELTA: -206

Reviewed-by: Johannes Thumshirn 
Signed-off-by: David Sterba

btrfs: use cached value of fs_info::csum_size everywhere

2020-12-08T14:53:59+00:00

btrfs_get_16 shows up in the system performance profiles (helper to read
16bit values from on-disk structures). This is partially because of the
checksum size that's frequently read along with data reads/writes, other
u16 uses are from item size or directory entries.

Replace all calls to btrfs_super_csum_size by the cached value from
fs_info.

Reviewed-by: Johannes Thumshirn 
Reviewed-by: Qu Wenruo 
Signed-off-by: David Sterba

btrfs: introduce mount option rescue=ignorebadroots

2020-12-08T14:53:41+00:00

In the face of extent root corruption, or any other core fs wide root
corruption we will fail to mount the file system.  This makes recovery
kind of a pain, because you need to fall back to userspace tools to
scrape off data.  Instead provide a mechanism to gracefully handle bad
roots, so we can at least mount read-only and possibly recover data from
the file system.

Signed-off-by: Josef Bacik 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: push the NODATASUM check into btrfs_lookup_bio_sums

2020-12-08T14:53:39+00:00

When we move to being able to handle NULL csum_roots it'll be cleaner to
just check in btrfs_lookup_bio_sums instead of at all of the caller
locations, so push the NODATASUM check into it as well so it's unified.

Reviewed-by: Johannes Thumshirn 
Reviewed-by: Qu Wenruo 
Signed-off-by: Josef Bacik 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: compression: move declarations to header

2020-10-07T10:06:55+00:00

The declarations of compression algorithm callbacks are defined in the
.c file as they're used from there. Compiler warns that there are no
declarations for public functions when compiling lzo.c/zlib.c/zstd.c.
Fix that by moving the declarations to the header as it's the common
place for all of them.

Reviewed-by: Josef Bacik 
Signed-off-by: David Sterba

btrfs: remove fail label in check_compressed_csum

2020-07-27T10:55:42+00:00

Signed-off-by: Nikolay Borisov 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: increment corrupt device counter during compressed read

2020-07-27T10:55:40+00:00

If a compressed read fails due to checksum error only a line is printed
to dmesg, device corrupt counter is not modified.

Reviewed-by: Josef Bacik 
Reviewed-by: Johannes Thumshirn 
Signed-off-by: Nikolay Borisov 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba