From a23eaa875f0f1d89eb866b8c9860e78273ff5daf Mon Sep 17 00:00:00 2001 From: Liu Bo Date: Fri, 4 Nov 2016 12:20:54 -0700 Subject: [PATCH] Btrfs: adjust len of writes if following a preallocated extent If we have |0--hole--4095||4096--preallocate--12287| instead of using preallocated space, a 8K direct write will just create a new 8K extent and it'll end up with |0--new extent--8191||8192--preallocate--12287| It's because we find a hole em and then go to create a new 8K extent directly without adjusting @len. Signed-off-by: Liu Bo Reviewed-by: Chris Mason Signed-off-by: David Sterba --- fs/btrfs/inode.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 06dc95caa6f1..66c1d65bd476 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -7782,10 +7782,12 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock, } /* - * this will cow the extent, reset the len in case we changed - * it above + * this will cow the extent, if em is within [start, len], then + * probably we've found a preallocated/existing extent, let's + * give it a chance to use preallocated space. */ - len = bh_result->b_size; + len = min_t(u64, bh_result->b_size, em->len - (start - em->start)); + len = ALIGN(len, root->sectorsize); free_extent_map(em); em = btrfs_new_extent_direct(inode, start, len); if (IS_ERR(em)) { -- 2.11.0