btrfs: use blocksize to check if compression is making things larger

[BEHAVIOR DIFFERENCE BETWEEN COMPRESSION ALGOS]
Currently LZO compression algorithm will check if we're making the
compressed data larger after compressing more than 2 blocks.

But zlib and zstd do the same checks after compressing more than 8192
bytes.

This is not a big deal, but since we're already supporting larger block
size (e.g. 64K block size if page size is also 64K), this check is not
suitable for all block sizes.

For example, if our page and block size are both 16KiB, and after the
first block compressed using zlib, the resulted compressed data is
slightly  larger than 16KiB, we will immediately abort the compression.

This makes zstd and zlib compression algorithms to behave slightly
different from LZO, which only aborts after compressing two blocks.

[ENHANCEMENT]
To unify the behavior, only abort the compression after compressing at
least two blocks.

Reviewed-by: Anand Jain <[email protected]>
Signed-off-by: Qu Wenruo <[email protected]>
Reviewed-by: David Sterba <[email protected]>
Signed-off-by: David Sterba <[email protected]>

Author: adam900710

fs/btrfs/zlib.c

@@ -148,6 +148,7 @@ int zlib_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
 	unsigned long len = *total_out;
 	unsigned long nr_dest_folios = *out_folios;
 	const unsigned long max_out = nr_dest_folios * PAGE_SIZE;
+	const u32 blocksize = inode->root->fs_info->sectorsize;
 	const u64 orig_end = start + len;
 
 	*out_folios = 0;
@@ -234,7 +235,7 @@ int zlib_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
 		}
 
 		/* we're making it bigger, give up */
-		if (workspace->strm.total_in > 8192 &&
+		if (workspace->strm.total_in > blocksize * 2 &&
 		    workspace->strm.total_in <
 		    workspace->strm.total_out) {
 			ret = -E2BIG;

fs/btrfs/zstd.c

@@ -400,6 +400,7 @@ int zstd_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
 	unsigned long len = *total_out;
 	const unsigned long nr_dest_folios = *out_folios;
 	const u64 orig_end = start + len;
+	const u32 blocksize = inode->root->fs_info->sectorsize;
 	unsigned long max_out = nr_dest_folios * PAGE_SIZE;
 	unsigned int cur_len;
 
@@ -456,7 +457,7 @@ int zstd_compress_folios(struct list_head *ws, struct btrfs_inode *inode,
 		}
 
 		/* Check to see if we are making it bigger */
-		if (tot_in + workspace->in_buf.pos > 8192 &&
+		if (tot_in + workspace->in_buf.pos > blocksize * 2 &&
 				tot_in + workspace->in_buf.pos <
 				tot_out + workspace->out_buf.pos) {
 			ret = -E2BIG;