From 6bc5636a67bf489d95ebc06c0449396fd487d309 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Wed, 6 Jan 2021 09:01:41 +0800 Subject: [PATCH] btrfs: refactor __extent_writepage_io() to improve readability The refactoring involves the following modifications: - iosize alignment In fact we don't really need to manually do alignment at all. All extent maps should already be aligned, thus basic ASSERT() check would be enough. - redundant variables We have extra variable like blocksize/pg_offset/end. They are all unnecessary. @blocksize can be replaced by sectorsize size directly, and it's only used to verify the em start/size is aligned. @pg_offset can be easily calculated using @cur and page_offset(page). @end is just assigned from @page_end and never modified, use "start + PAGE_SIZE - 1" directly and remove @page_end. - remove some BUG_ON()s The BUG_ON()s are for extent map, which we have tree-checker to check on-disk extent data item and runtime check. ASSERT() should be enough. Reviewed-by: Josef Bacik Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/extent_io.c | 37 ++++++++++++++++--------------------- 1 file changed, 16 insertions(+), 21 deletions(-) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 60990616b895..74c0a32d04fc 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -3513,23 +3513,20 @@ static noinline_for_stack int __extent_writepage_io(struct btrfs_inode *inode, unsigned long nr_written, int *nr_ret) { + struct btrfs_fs_info *fs_info = inode->root->fs_info; struct extent_io_tree *tree = &inode->io_tree; u64 start = page_offset(page); - u64 page_end = start + PAGE_SIZE - 1; - u64 end; + u64 end = start + PAGE_SIZE - 1; u64 cur = start; u64 extent_offset; u64 block_start; - u64 iosize; struct extent_map *em; - size_t pg_offset = 0; - size_t blocksize; int ret = 0; int nr = 0; const unsigned int write_flags = wbc_to_write_flags(wbc); bool compressed; - ret = btrfs_writepage_cow_fixup(page, start, page_end); + ret = btrfs_writepage_cow_fixup(page, start, end); if (ret) { /* Fixup worker will requeue */ redirty_page_for_writepage(wbc, page); @@ -3544,16 +3541,13 @@ static noinline_for_stack int __extent_writepage_io(struct btrfs_inode *inode, */ update_nr_written(wbc, nr_written + 1); - end = page_end; - blocksize = inode->vfs_inode.i_sb->s_blocksize; - while (cur <= end) { u64 disk_bytenr; u64 em_end; + u32 iosize; if (cur >= i_size) { - btrfs_writepage_endio_finish_ordered(page, cur, - page_end, 1); + btrfs_writepage_endio_finish_ordered(page, cur, end, 1); break; } em = btrfs_get_extent(inode, NULL, 0, cur, end - cur + 1); @@ -3565,13 +3559,16 @@ static noinline_for_stack int __extent_writepage_io(struct btrfs_inode *inode, extent_offset = cur - em->start; em_end = extent_map_end(em); - BUG_ON(em_end <= cur); - BUG_ON(end < cur); - iosize = min(em_end - cur, end - cur + 1); - iosize = ALIGN(iosize, blocksize); - disk_bytenr = em->block_start + extent_offset; + ASSERT(cur <= em_end); + ASSERT(cur < end); + ASSERT(IS_ALIGNED(em->start, fs_info->sectorsize)); + ASSERT(IS_ALIGNED(em->len, fs_info->sectorsize)); block_start = em->block_start; compressed = test_bit(EXTENT_FLAG_COMPRESSED, &em->flags); + disk_bytenr = em->block_start + extent_offset; + + /* Note that em_end from extent_map_end() is exclusive */ + iosize = min(em_end, end + 1) - cur; free_extent_map(em); em = NULL; @@ -3587,7 +3584,6 @@ static noinline_for_stack int __extent_writepage_io(struct btrfs_inode *inode, btrfs_writepage_endio_finish_ordered(page, cur, cur + iosize - 1, 1); cur += iosize; - pg_offset += iosize; continue; } @@ -3599,8 +3595,8 @@ static noinline_for_stack int __extent_writepage_io(struct btrfs_inode *inode, } ret = submit_extent_page(REQ_OP_WRITE | write_flags, wbc, - page, disk_bytenr, iosize, pg_offset, - &epd->bio, + page, disk_bytenr, iosize, + cur - page_offset(page), &epd->bio, end_bio_extent_writepage, 0, 0, 0, false); if (ret) { @@ -3609,8 +3605,7 @@ static noinline_for_stack int __extent_writepage_io(struct btrfs_inode *inode, end_page_writeback(page); } - cur = cur + iosize; - pg_offset += iosize; + cur += iosize; nr++; } *nr_ret = nr; -- 2.20.1