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 <bo.li.liu@xxxxxxxxxx>
---
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 2b790bd..48e9356 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7783,10 +7783,12 @@ 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)) {
--
2.5.5
--
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