linux.git/fs/btrfs/compression.c, branch v6.10

btrfs: change root->root_key.objectid to btrfs_root_id()

2024-05-07T19:31:06+00:00

A comment from Filipe on one of my previous cleanups brought my
attention to a new helper we have for getting the root id of a root,
which makes it easier to read in the code.

The changes where made with the following Coccinelle semantic patch:

// 
@@
expression E,E1;
@@
(
 E->root_key.objectid = E1
|
- E->root_key.objectid
+ btrfs_root_id(E)
)
// 

Reviewed-by: Filipe Manana 
Signed-off-by: Josef Bacik 
Reviewed-by: David Sterba 
[ minor style fixups ]
Signed-off-by: David Sterba

btrfs: compression: migrate compression/decompression paths to folios

2024-05-07T19:31:02+00:00

For both compression and decompression paths, we always require a
"struct page **pages" and "unsigned long nr_pages", this involves quite
some part of the btrfs compression paths:

- All the compression entry points

- compressed_bio structure
  This affects both compression and decompression.

- async_extent structure

Unfortunately with all those involved parts, there is no good way to
split the conversion into smaller patches while still passing compiling.
So do this in one big conversion in one go.

Please note this is direct page->folio conversion, no change on the page
sized folio requirement yet.

Signed-off-by: Qu Wenruo 
Reviewed-by: David Sterba 
[ minor style fixups ]
Signed-off-by: David Sterba

btrfs: compression: convert page allocation to folio interfaces

2024-05-07T19:31:02+00:00

Currently we have two wrappers to allocate and free a page for
compression usage:

- btrfs_alloc_compr_page()
- btrfs_free_compr_page()

The allocator would try to grab a page from the pool, and only allocate
a new page if the pool is empty.

The reclaimer would check if the pool is full, and if not full it would
put the page into the pool.

This patch converts both helpers to use folio interfaces, and allowing
further conversion of compression path to folios.

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

btrfs: compression: add error handling for missed page cache

2024-05-07T19:31:02+00:00

For all the supported compression algorithms, the compression path would
always need to grab the page cache, then do the compression.

Normally we would get a page reference without any problem, since the
write path should have already locked the pages in the write range.
For the sake of error handling, we should handle the page cache miss
case.

Adds a common wrapper, btrfs_compress_find_get_page(), which calls
find_get_page(), and do the error handling along with an error message.

Callers inside compression path would only need to call
btrfs_compress_find_get_page(), and error out if it returned any error.

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

btrfs: compression: remove dead comments in btrfs_compress_heuristic()

2024-03-05T16:13:23+00:00

Since commit a440d48c7f93 ("Btrfs: heuristic: implement sampling
logic"), btrfs_compress_heuristic() is no longer a simple "return true",
but more complex to determine if we should compress.

Thus the comment is dead and can be confusing, just remove it.

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

btrfs: add helper to get fs_info from struct inode pointer

2024-03-04T15:24:49+00:00

Add a convenience helper to get a fs_info from a VFS inode pointer
instead of open coding the chain or using btrfs_sb() that in some cases
does one more pointer hop.  This is implemented as a macro (still with
type checking) so we don't need full definitions of struct btrfs_inode,
btrfs_root or btrfs_fs_info.

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

btrfs: add helpers to get fs_info from page/folio pointers

2024-03-04T15:24:49+00:00

Add convenience helpers to get a fs_info from a page or folio pointer
instead of open coding the chain or using btrfs_sb() that in some cases
does one more pointer hop.  This is implemented as a macro (still with
type checking) so we don't need full definitions of struct page, folio,
btrfs_root and btrfs_fs_info. The latter can't be static inlines as this
would create loop between ctree.h <-> fs.h, or the headers would have to
be restructured.

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

btrfs: remove unused included headers

2024-03-04T15:24:46+00:00

With help of neovim, LSP and clangd we can identify header files that
are not actually needed to be included in the .c files. This is focused
only on removal (with minor fixups), further cleanups are possible but
will require doing the header files properly with forward declarations,
minimized includes and include-what-you-use care.

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

btrfs: zlib: fix and simplify the inline extent decompression

2024-01-18T22:35:26+00:00

[BUG]

If we have a filesystem with 4k sectorsize, and an inlined compressed
extent created like this:

	item 4 key (257 INODE_ITEM 0) itemoff 15863 itemsize 160
		generation 8 transid 8 size 4096 nbytes 4096
		block group 0 mode 100600 links 1 uid 0 gid 0 rdev 0
		sequence 1 flags 0x0(none)
	item 5 key (257 INODE_REF 256) itemoff 15839 itemsize 24
		index 2 namelen 14 name: source_inlined
	item 6 key (257 EXTENT_DATA 0) itemoff 15770 itemsize 69
		generation 8 type 0 (inline)
		inline extent data size 48 ram_bytes 4096 compression 1 (zlib)

Which has an inline compressed extent at file offset 0, and its
decompressed size is 4K, allowing us to reflink that 4K range to another
location (which will not be compressed).

If we do such reflink on a subpage system, it would fail like this:

  # xfs_io -f -c "reflink $mnt/source_inlined 0 60k 4k" $mnt/dest
  XFS_IOC_CLONE_RANGE: Input/output error

[CAUSE]
In zlib_decompress(), we didn't treat @start_byte as just a page offset,
but also use it as an indicator on whether we should switch our output
buffer.

In reality, for subpage cases, although @start_byte can be non-zero,
we should never switch input/output buffer, since the whole input/output
buffer should never exceed one sector.

Note: The above assumption is only not true if we're going to support
multi-page sectorsize.

Thus the current code using @start_byte as a condition to switch
input/output buffer or finish the decompression is completely incorrect.

[FIX]
The fix involves several modifications:

- Rename @start_byte to @dest_pgoff to properly express its meaning

- Add an extra ASSERT() inside btrfs_decompress() to make sure the
  input/output size never exceeds one sector.

- Use Z_FINISH flag to make sure the decompression happens in one go

- Remove the loop needed to switch input/output buffers

- Use correct destination offset inside the destination page

- Consider early end as an error

After the fix, even on 64K page sized aarch64, above reflink now
works as expected:

  # xfs_io -f -c "reflink $mnt/source_inlined 0 60k 4k" $mnt/dest
  linked 4096/4096 bytes at offset 61440

And resulted a correct file layout:

	item 9 key (258 INODE_ITEM 0) itemoff 15542 itemsize 160
		generation 10 transid 10 size 65536 nbytes 4096
		block group 0 mode 100600 links 1 uid 0 gid 0 rdev 0
		sequence 1 flags 0x0(none)
	item 10 key (258 INODE_REF 256) itemoff 15528 itemsize 14
		index 3 namelen 4 name: dest
	item 11 key (258 XATTR_ITEM 3817753667) itemoff 15445 itemsize 83
		location key (0 UNKNOWN.0 0) type XATTR
		transid 10 data_len 37 name_len 16
		name: security.selinux
		data unconfined_u:object_r:unlabeled_t:s0
	item 12 key (258 EXTENT_DATA 61440) itemoff 15392 itemsize 53
		generation 10 type 1 (regular)
		extent data disk byte 13631488 nr 4096
		extent data offset 0 nr 4096 ram 4096
		extent compression 0 (none)

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

btrfs: migrate various end io functions to folios

2023-12-15T22:03:58+00:00

If we still go the old page based iterator functions, like
bio_for_each_segment_all(), we can hit middle pages of a folio (compound
page).

In that case if we set any page flag on those middle pages, we can
easily trigger VM_BUG_ON(), as for compound page flags, they should
follow their flag policies (normally only set on leading or tail pages).

To avoid such problem in the future full folio migration, here we do:

- Change from bio_for_each_segment_all() to bio_for_each_folio_all()
  This completely removes the ability to access the middle page.

- Add extra ASSERT()s for data read/write paths
  To ensure we only get single paged folio for data now.

- Rename those end io functions to follow a certain schema
  * end_bbio_compressed_read()
  * end_bbio_compressed_write()

    These two endio functions don't set any page flags, as they use pages
    not mapped to any address space.
    They can be very good candidates for higher order folio testing.

    And they are shared between compression and encoded IO.

  * end_bbio_data_read()
  * end_bbio_data_write()
  * end_bbio_meta_read()
  * end_bbio_meta_write()

  The old function names are not unified:
    - end_bio_extent_writepage()
    - end_bio_extent_readpage()
    - extent_buffer_write_end_io()
    - extent_buffer_read_end_io()

  They share no schema on where the "end_*io" string should be, nor can
  be confusing just using "extent_buffer" and "extent" to distinguish
  data and metadata paths.

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