From 2c73162d649670045415537dc746f7524cda1405 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 28 Jun 2023 17:31:30 +0200 Subject: [PATCH] btrfs: improve the delalloc_to_write calculation in writepage_delalloc Currently writepage_delalloc adds to delalloc_to_write in every loop operation. That is not only more work than doing it once after the loop, but can also over-increment the counter due to rounding errors when a new loop iteration starts with an offset into a page. Add a new page_start variable instead of recaculation that value over and over, move the delalloc_to_write calculation out of the loop, use the DIV_ROUND_UP helper instead of open coding it and remove the pointless found local variable. Reviewed-by: Josef Bacik Signed-off-by: Christoph Hellwig Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/extent_io.c | 29 ++++++++++++++--------------- 1 file changed, 14 insertions(+), 15 deletions(-) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 4981058..148d289 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -1185,8 +1185,10 @@ static inline void contiguous_readpages(struct page *pages[], int nr_pages, static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode, struct page *page, struct writeback_control *wbc) { - const u64 page_end = page_offset(page) + PAGE_SIZE - 1; - u64 delalloc_start = page_offset(page); + const u64 page_start = page_offset(page); + const u64 page_end = page_start + PAGE_SIZE - 1; + u64 delalloc_start = page_start; + u64 delalloc_end = page_end; u64 delalloc_to_write = 0; /* How many pages are started by btrfs_run_delalloc_range() */ unsigned long nr_written = 0; @@ -1194,13 +1196,9 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode, int page_started = 0; while (delalloc_start < page_end) { - u64 delalloc_end = page_end; - bool found; - - found = find_lock_delalloc_range(&inode->vfs_inode, page, - &delalloc_start, - &delalloc_end); - if (!found) { + delalloc_end = page_end; + if (!find_lock_delalloc_range(&inode->vfs_inode, page, + &delalloc_start, &delalloc_end)) { delalloc_start = delalloc_end + 1; continue; } @@ -1209,14 +1207,15 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode, if (ret) return ret; - /* - * delalloc_end is already one less than the total length, so - * we don't subtract one from PAGE_SIZE - */ - delalloc_to_write += (delalloc_end - delalloc_start + - PAGE_SIZE) >> PAGE_SHIFT; delalloc_start = delalloc_end + 1; } + + /* + * delalloc_end is already one less than the total length, so + * we don't subtract one from PAGE_SIZE + */ + delalloc_to_write += + DIV_ROUND_UP(delalloc_end + 1 - page_start, PAGE_SIZE); if (wbc->nr_to_write < delalloc_to_write) { int thresh = 8192; -- 2.7.4