From be6a13613fd35602ea9e65d6634cf7af79f0a93d Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Thu, 4 Feb 2021 15:03:23 +0800 Subject: [PATCH] btrfs: make btrfs_submit_compressed_read() subpage compatible For compressed read, we always submit page read using page size. This doesn't work well with subpage, as for subpage one page can contain several sectors. Such submission will read range out of what we want, and cause problems. Thankfully to make it subpage compatible, we only need to change how the last page of the compressed extent is read. Instead of always adding a full page to the compressed read bio, if we're at the last page, calculate the size using compressed length, so that we only add part of the range into the compressed read bio. Since we are here, also change the PAGE_SIZE used in lookup_extent_mapping() to sectorsize. This modification won't cause any functional change, as lookup_extent_mapping() can handle the case where the search range is larger than found extent range. Reviewed-by: Anand Jain Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/compression.c | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-) diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index 6d203ac..5bad3a0 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -640,7 +640,7 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, read_lock(&em_tree->lock); em = lookup_extent_mapping(em_tree, page_offset(bio_first_page_all(bio)), - PAGE_SIZE); + fs_info->sectorsize); read_unlock(&em_tree->lock); if (!em) return BLK_STS_IOERR; @@ -698,19 +698,30 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, refcount_set(&cb->pending_bios, 1); for (pg_index = 0; pg_index < nr_pages; pg_index++) { + u32 pg_len = PAGE_SIZE; int submit = 0; + /* + * To handle subpage case, we need to make sure the bio only + * covers the range we need. + * + * If we're at the last page, truncate the length to only cover + * the remaining part. + */ + if (pg_index == nr_pages - 1) + pg_len = min_t(u32, PAGE_SIZE, + compressed_len - pg_index * PAGE_SIZE); + page = cb->compressed_pages[pg_index]; page->mapping = inode->i_mapping; page->index = em_start >> PAGE_SHIFT; if (comp_bio->bi_iter.bi_size) - submit = btrfs_bio_fits_in_stripe(page, PAGE_SIZE, + submit = btrfs_bio_fits_in_stripe(page, pg_len, comp_bio, 0); page->mapping = NULL; - if (submit || bio_add_page(comp_bio, page, PAGE_SIZE, 0) < - PAGE_SIZE) { + if (submit || bio_add_page(comp_bio, page, pg_len, 0) < pg_len) { unsigned int nr_sectors; ret = btrfs_bio_wq_end_io(fs_info, comp_bio, @@ -743,9 +754,9 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, comp_bio->bi_private = cb; comp_bio->bi_end_io = end_compressed_bio_read; - bio_add_page(comp_bio, page, PAGE_SIZE, 0); + bio_add_page(comp_bio, page, pg_len, 0); } - cur_disk_byte += PAGE_SIZE; + cur_disk_byte += pg_len; } ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA); -- 2.7.4