| Message ID | 20200915154140.mlmlwmctre2prf2s@fiona (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: use iosize while reading compressed pages | expand |
On 9/15/20 11:41 AM, Goldwyn Rodrigues wrote: > While using compression, a submitted bio is mapped with a compressed bio > which performs the read from disk, decompresses and returns uncompressed > data to original bio. The original bio must reflect the uncompressed > size (iosize) of the I/O to be performed, or else the page just gets the > decompressed I/O length of data (disk_io_size). The compressed bio > checks the extent map and get the correct length while performing the > I/O from disk. > > This came up in subpage work when only compressed length of the original > bio was filled in the page. This worked correctly for pagesize == > sectorsize because both compressed and uncompressed data are at pagesize > boundaries, and would end up filling the requested page. > > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Thanks, Josef
On Tue, Sep 15, 2020 at 10:41:40AM -0500, Goldwyn Rodrigues wrote: > While using compression, a submitted bio is mapped with a compressed bio > which performs the read from disk, decompresses and returns uncompressed > data to original bio. The original bio must reflect the uncompressed > size (iosize) of the I/O to be performed, or else the page just gets the > decompressed I/O length of data (disk_io_size). The compressed bio > checks the extent map and get the correct length while performing the > I/O from disk. > > This came up in subpage work when only compressed length of the original > bio was filled in the page. This worked correctly for pagesize == > sectorsize because both compressed and uncompressed data are at pagesize > boundaries, and would end up filling the requested page. > > Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com> Added to misc-next, thanks.
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index afac70ef0cc5..98173580a948 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -3158,7 +3158,6 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached, int nr = 0; size_t pg_offset = 0; size_t iosize; - size_t disk_io_size; size_t blocksize = inode->i_sb->s_blocksize; unsigned long this_bio_flag = 0; struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree; @@ -3224,13 +3223,10 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached, iosize = min(extent_map_end(em) - cur, end - cur + 1); cur_end = min(extent_map_end(em) - 1, end); iosize = ALIGN(iosize, blocksize); - if (this_bio_flag & EXTENT_BIO_COMPRESSED) { - disk_io_size = em->block_len; + if (this_bio_flag & EXTENT_BIO_COMPRESSED) offset = em->block_start; - } else { + else offset = em->block_start + extent_offset; - disk_io_size = iosize; - } block_start = em->block_start; if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) block_start = EXTENT_MAP_HOLE; @@ -3319,7 +3315,7 @@ int btrfs_do_readpage(struct page *page, struct extent_map **em_cached, } ret = submit_extent_page(REQ_OP_READ | read_flags, NULL, - page, offset, disk_io_size, + page, offset, iosize, pg_offset, bio, end_bio_extent_readpage, 0, *bio_flags,
While using compression, a submitted bio is mapped with a compressed bio which performs the read from disk, decompresses and returns uncompressed data to original bio. The original bio must reflect the uncompressed size (iosize) of the I/O to be performed, or else the page just gets the decompressed I/O length of data (disk_io_size). The compressed bio checks the extent map and get the correct length while performing the I/O from disk. This came up in subpage work when only compressed length of the original bio was filled in the page. This worked correctly for pagesize == sectorsize because both compressed and uncompressed data are at pagesize boundaries, and would end up filling the requested page. Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com> --- fs/btrfs/extent_io.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-)