From a196a8944f77b7b762795a0862d8aa4a005625a4 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Fri, 16 Sep 2022 15:28:37 +0800 Subject: [PATCH] btrfs: do not reset extent map members for inline extents read Currently for inline extents read inside btrfs_get_extent(), we will reset several extent map members: - em->start Reset to extent_start, which is completely unnecessary. The extent_start and em->start should have already be zero, ensured by tree-checker already. - em->len Reset the round_up(copy_size, fs_info->sectorsize), which is again unnecessary. - em->orig_block_len Reset to em->len (sectorsize), while it is originally unset from btrfs_extent_item_to_extent_map(). This makes no difference, as all extent map handling paths will ignore the orig_block_len if they found it's an inlined extent. Such inline extent orig_block_len ignoring examples can be found in btrfs_drop_extent_cache(). - em->orig_start Reset to em->start (0), while it is originally set to EXTENT_MAP_HOLE. This makes no difference either, as all extent map handling paths will ignore the em->orig_start if they found it's an inline extent. Thus all these em members resetting are unnecessary. Replace them with ASSERT()s checking the only two members (block_start and length) that make sense. Signed-off-by: Qu Wenruo Signed-off-by: David Sterba --- fs/btrfs/inode.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index a374dd718315..5b45eb141215 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -7082,10 +7082,15 @@ next: copy_size = min_t(u64, PAGE_SIZE, btrfs_file_extent_ram_bytes(leaf, item)); - em->start = extent_start; - em->len = ALIGN(copy_size, fs_info->sectorsize); - em->orig_block_len = em->len; - em->orig_start = em->start; + + /* + * btrfs_extent_item_to_extent_map() should have properly + * initialized em members already. + * + * Other members are not utilized for inline extents. + */ + ASSERT(em->block_start == EXTENT_MAP_INLINE); + ASSERT(em->len = fs_info->sectorsize); if (!PageUptodate(page)) { if (btrfs_file_extent_compression(leaf, item) !=