[PATCH 2/2] btrfs: reduce the size of compressed_bio

[Qu Wenruo <wqu@suse.com>]

The member compressed_bio::compressed_len can be replaced by the bio
size, as we always submit the full compressed data without any partial
read/write.

Furthermore we already have enough ASSERT()s making sure the bio size
matches the ordered extent or the extent map.

This saves 8 bytes from compressed_bio:

Before:

struct compressed_bio {
        u64                        start;                /*     0     8 */
        unsigned int               len;                  /*     8     4 */
        unsigned int               compressed_len;       /*    12     4 */
        u8                         compress_type;        /*    16     1 */
        bool                       writeback;            /*    17     1 */

        /* XXX 6 bytes hole, try to pack */

        struct btrfs_bio *         orig_bbio;            /*    24     8 */
        struct btrfs_bio           bbio __attribute__((__aligned__(8))); /*    32   304 */

        /* XXX last struct has 1 bit hole */

        /* size: 336, cachelines: 6, members: 7 */
        /* sum members: 330, holes: 1, sum holes: 6 */
        /* member types with bit holes: 1, total: 1 */
        /* forced alignments: 1 */
        /* last cacheline: 16 bytes */
} __attribute__((__aligned__(8)));

After:

 struct compressed_bio {
        u64                        start;                /*     0     8 */
        unsigned int               len;                  /*     8     4 */
        u8                         compress_type;        /*    12     1 */
        bool                       writeback;            /*    13     1 */

        /* XXX 2 bytes hole, try to pack */

        struct btrfs_bio *         orig_bbio;            /*    16     8 */
        struct btrfs_bio           bbio __attribute__((__aligned__(8))); /*    24   304 */

        /* XXX last struct has 1 bit hole */

        /* size: 328, cachelines: 6, members: 6 */
        /* sum members: 326, holes: 1, sum holes: 2 */
        /* member types with bit holes: 1, total: 1 */
        /* forced alignments: 1 */
        /* last cacheline: 8 bytes */
} __attribute__((__aligned__(8)));

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/compression.c | 2 --
 fs/btrfs/compression.h | 3 ---
 fs/btrfs/lzo.c         | 7 ++++---
 fs/btrfs/zlib.c        | 2 +-
 fs/btrfs/zstd.c        | 2 +-
 5 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 64600b6458cb..3a33c8fa96c8 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -330,7 +330,6 @@ void btrfs_submit_compressed_write(struct btrfs_ordered_extent *ordered,
 	cb->start = ordered->file_offset;
 	cb->len = ordered->num_bytes;
 	ASSERT(cb->bbio.bio.bi_iter.bi_size == ordered->disk_num_bytes);
-	cb->compressed_len = ordered->disk_num_bytes;
 	cb->bbio.bio.bi_iter.bi_sector = ordered->disk_bytenr >> SECTOR_SHIFT;
 	cb->bbio.ordered = ordered;
 
@@ -560,7 +559,6 @@ void btrfs_submit_compressed_read(struct btrfs_bio *bbio)
 	em_start = em->start;
 
 	cb->len = bbio->bio.bi_iter.bi_size;
-	cb->compressed_len = compressed_len;
 	cb->compress_type = btrfs_extent_map_compression(em);
 	cb->orig_bbio = bbio;
 	cb->bbio.csum_search_commit_root = bbio->csum_search_commit_root;
diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
index 65b8bc4bbe0b..84600b284e1e 100644
--- a/fs/btrfs/compression.h
+++ b/fs/btrfs/compression.h
@@ -48,9 +48,6 @@ struct compressed_bio {
 	/* Number of bytes in the inode we're working on */
 	unsigned int len;
 
-	/* Number of bytes on disk */
-	unsigned int compressed_len;
-
 	/* The compression algorithm for this bio */
 	u8 compress_type;
 
diff --git a/fs/btrfs/lzo.c b/fs/btrfs/lzo.c
index 971c2ea98e18..fdcce71c2326 100644
--- a/fs/btrfs/lzo.c
+++ b/fs/btrfs/lzo.c
@@ -431,6 +431,7 @@ int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 	struct workspace *workspace = list_entry(ws, struct workspace, list);
 	struct btrfs_fs_info *fs_info = cb->bbio.inode->root->fs_info;
 	const u32 sectorsize = fs_info->sectorsize;
+	const u32 compressed_len = bio_get_size(&cb->bbio.bio);
 	struct folio_iter fi;
 	char *kaddr;
 	int ret;
@@ -460,14 +461,14 @@ int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 	 * and all sectors should be used.
 	 * If this happens, it means the compressed extent is corrupted.
 	 */
-	if (unlikely(len_in > min_t(size_t, BTRFS_MAX_COMPRESSED, cb->compressed_len) ||
-		     round_up(len_in, sectorsize) < cb->compressed_len)) {
+	if (unlikely(len_in > min_t(size_t, BTRFS_MAX_COMPRESSED, compressed_len) ||
+		     round_up(len_in, sectorsize) < compressed_len)) {
 		struct btrfs_inode *inode = cb->bbio.inode;
 
 		btrfs_err(fs_info,
 "lzo header invalid, root %llu inode %llu offset %llu lzo len %u compressed len %u",
 			  btrfs_root_id(inode->root), btrfs_ino(inode),
-			  cb->start, len_in, cb->compressed_len);
+			  cb->start, len_in, compressed_len);
 		return -EUCLEAN;
 	}
 
diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index 0a8fcee16428..49676ad87815 100644
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -349,7 +349,7 @@ int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 	int wbits = MAX_WBITS;
 	char *data_in;
 	size_t total_out = 0;
-	size_t srclen = cb->compressed_len;
+	const size_t srclen = bio_get_size(&cb->bbio.bio);
 	unsigned long buf_start;
 
 	bio_first_folio(&fi, &cb->bbio.bio, 0);
diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
index c002d18666b7..3abb2b98caca 100644
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -587,7 +587,7 @@ int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 	struct btrfs_fs_info *fs_info = cb_to_fs_info(cb);
 	struct workspace *workspace = list_entry(ws, struct workspace, list);
 	struct folio_iter fi;
-	size_t srclen = cb->compressed_len;
+	size_t srclen = bio_get_size(&cb->bbio.bio);
 	zstd_dstream *stream;
 	int ret = 0;
 	const u32 blocksize = fs_info->sectorsize;
-- 
2.52.0