kernel/git/stable/linux.git/fs/btrfs/compression.h, branch linux-5.19.y

btrfs: derive compression type from extent map during reads

2022-05-16T15:17:31+00:00

Derive the compression type from extent map as opposed to the bio flags passed. This makes it more precise and not reliant on function parameters. Reviewed-by: Nikolay Borisov Signed-off-by: Goldwyn Rodrigues Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: do not return errors from btrfs_submit_compressed_read

2022-05-16T15:03:14+00:00

btrfs_submit_compressed_read already calls ->bi_end_io on error and the caller must ignore the return value, so remove it. Reviewed-by: Nikolay Borisov Reviewed-by: Qu Wenruo Signed-off-by: Christoph Hellwig Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: track compressed bio errors as blk_status_t

2022-03-14T12:13:51+00:00

Right now we just have a binary "errors" flag, so any error we get on the compressed bio's gets translated to EIO. This isn't necessarily a bad thing, but if we get an ENOMEM it may be nice to know that's what happened instead of an EIO. Track our errors as a blk_status_t, and do the appropriate setting of the errors accordingly. Signed-off-by: Josef Bacik Signed-off-by: David Sterba

btrfs: add BTRFS_IOC_ENCODED_WRITE

2022-03-14T12:13:51+00:00

The implementation resembles direct I/O: we have to flush any ordered extents, invalidate the page cache, and do the io tree/delalloc/extent map/ordered extent dance. From there, we can reuse the compression code with a minor modification to distinguish the write from writeback. This also creates inline extents when possible. Signed-off-by: Omar Sandoval Signed-off-by: David Sterba

btrfs: replace BUILD_BUG_ON by static_assert

2022-03-14T12:13:49+00:00

The static_assert introduced in 6bab69c65013 ("build_bug.h: add wrapper for _Static_assert") has been supported by compilers for a long time (gcc 4.6, clang 3.0) and can be used in header files. We don't need to put BUILD_BUG_ON to random functions but rather keep it next to the definition. The exception here is the UAPI header btrfs_tree.h that could be potentially included by userspace code and the static assert is not defined (nor used in any other header). Reviewed-by: Johannes Thumshirn Signed-off-by: David Sterba

btrfs: determine stripe boundary at bio allocation time in btrfs_submit_compressed_write

2021-10-26T17:08:04+00:00

Currently btrfs_submit_compressed_write() will check btrfs_bio_fits_in_stripe() each time a new page is going to be added. Even if compressed extent is small, we don't really need to do that for every page. Align the behavior to extent_io.c, by determining the stripe boundary when allocating a bio. Unlike extent_io.c, in compressed.c we don't need to bother things like different bio flags, thus no need to re-use bio_ctrl. Here we just manually introduce new local variable, next_stripe_start, and use that value returned from alloc_compressed_bio() to calculate the stripe boundary. Then each time we add some page range into the bio, we check if we reached the boundary. And if reached, submit it. Also, since we have @cur_disk_bytenr to determine whether we're the last bio, we don't need a explicit last_bio: tag for error handling any more. And since we use @cur_disk_bytenr to wait, there is no need for pending_bios, also remove it to save some memory of compressed_bio. Signed-off-by: Qu Wenruo Signed-off-by: David Sterba

btrfs: introduce compressed_bio::pending_sectors to trace compressed bio

2021-10-26T17:08:03+00:00

For btrfs_submit_compressed_read() and btrfs_submit_compressed_write(), we have a pretty weird dance around compressed_bio::pending_bios: btrfs_submit_compressed_read/write() { cb = kmalloc() refcount_set(&cb->pending_bios, 0); bio = btrfs_alloc_bio(); /* NOTE here, we haven't yet submitted any bio */ refcount_set(&cb->pending_bios, 1); for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) { if (submit) { /* Here we submit bio, but we always have one * extra pending_bios */ refcount_inc(&cb->pending_bios); ret = btrfs_map_bio(); } } /* Submit the last bio */ ret = btrfs_map_bio(); } There are two reasons why we do this: - compressed_bio::pending_bios is a refcount Thus if it's reduced to 0, it can not be increased again. - To ensure the compressed_bio is not freed by some submitted bios If the submitted bio is finished before the next bio submitted, we can free the compressed_bio completely. But the above code is sometimes confusing, and we can do it better by introducing a new member, compressed_bio::pending_sectors. Now we use compressed_bio::pending_sectors to indicate whether we have any pending sectors under IO or not yet submitted. If pending_sectors == 0, we're definitely the last bio of compressed_bio, and is OK to release the compressed bio. Now the workflow looks like this: btrfs_submit_compressed_read/write() { cb = kmalloc() atomic_set(&cb->pending_bios, 0); refcount_set(&cb->pending_sectors, compressed_len >> sectorsize_bits); bio = btrfs_alloc_bio(); for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) { if (submit) { refcount_inc(&cb->pending_bios); ret = btrfs_map_bio(); } } /* Submit the last bio */ refcount_inc(&cb->pending_bios); ret = btrfs_map_bio(); } For now we still need pending_bios for later error handling, but will remove pending_bios eventually after properly handling the errors. Signed-off-by: Qu Wenruo Signed-off-by: David Sterba

btrfs: rework btrfs_decompress_buf2page()

2021-08-23T11:19:04+00:00

There are several bugs inside the function btrfs_decompress_buf2page() - @start_byte doesn't take bvec.bv_offset into consideration Thus it can't handle case where the target range is not page aligned. - Too many helper variables There are tons of helper variables, @buf_offset, @current_buf_start, @start_byte, @prev_start_byte, @working_bytes, @bytes. This hurts anyone who wants to read the function. - No obvious main cursor for the iteartion A new problem caused by previous problem. - Comments for parameter list makes no sense Like @buf_start is the offset to @buf, or offset inside the full decompressed extent? (Spoiler alert, the later case) And @total_out acts more like @buf_start + @size_of_buf. The worst is @disk_start. The real meaning of it is the file offset of the full decompressed extent. This patch will rework the whole function by: - Add a proper comment with ASCII art to explain the parameter list - Rework parameter list The old @buf_start is renamed to @decompressed, to show how many bytes are already decompressed inside the full decompressed extent. The old @total_out is replaced by @buf_len, which is the decompressed data size. For old @disk_start and @bio, just pass @compressed_bio in. - Use single main cursor The main cursor will be @cur_file_offset, to show what's the current file offset. Other helper variables will be declared inside the main loop, and only minimal amount of helper variables: * offset_inside_decompressed_buf: The only real helper * copy_start_file_offset: File offset we start memcpy * bvec_file_offset: File offset of current bvec Even with all these extensive comments, the final function is still smaller than the original function, which is definitely a win. Signed-off-by: Qu Wenruo Signed-off-by: David Sterba

btrfs: optimize variables size in btrfs_submit_compressed_write

2021-06-21T13:19:07+00:00

Patch "btrfs: reduce compressed_bio member's types" reduced some member's size. Function arguments @len, @compressed_len and @nr_pages can be declared as unsigned int. Signed-off-by: Anand Jain Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: reduce compressed_bio members' types

2021-06-21T13:19:06+00:00

Several members of compressed_bio are of type that's unnecessarily big for the values that they'd hold: - the size of the uncompressed and compressed data is 128K now, we can keep is as int - same for number of pages - the compress type fits to a byte - the errors is 0/1 The size of the unpatched structure is 80 bytes with several holes. Reordering nr_pages next to the pages the hole after pending_bios is filled and the resulting size is 56 bytes. This keeps the csums array aligned to 8 bytes, which is nice. Further size optimizations may be possible but right now it looks good to me: struct compressed_bio { refcount_t pending_bios; /* 0 4 */ unsigned int nr_pages; /* 4 4 */ struct page * * compressed_pages; /* 8 8 */ struct inode * inode; /* 16 8 */ u64 start; /* 24 8 */ unsigned int len; /* 32 4 */ unsigned int compressed_len; /* 36 4 */ u8 compress_type; /* 40 1 */ u8 errors; /* 41 1 */ /* XXX 2 bytes hole, try to pack */ int mirror_num; /* 44 4 */ struct bio * orig_bio; /* 48 8 */ u8 sums[]; /* 56 0 */ /* size: 56, cachelines: 1, members: 12 */ /* sum members: 54, holes: 1, sum holes: 2 */ /* last cacheline: 56 bytes */ }; Reviewed-by: Anand Jain Signed-off-by: David Sterba