@@ -1591,8 +1591,10 @@ static void btrfs_merge_extent_hook(struct inode *inode,
if (!(other->state & EXTENT_DELALLOC))
return;
- old_size = other->end - other->start + 1;
- new_size = old_size + (new->end - new->start + 1);
+ if (new->start > other->start)
+ new_size = new->end - other->start + 1;
+ else
+ new_size = other->end - new->start + 1;
/* we're not bigger than the max, unreserve the space and go */
if (new_size <= BTRFS_MAX_EXTENT_SIZE) {
@@ -1603,13 +1605,32 @@ static void btrfs_merge_extent_hook(struct inode *inode,
}
/*
- * If we grew by another max_extent, just return, we want to keep that
- * reserved amount.
+ * We have to add up either side to figure out how many extents were
+ * accounted for before we merged into one big extent. If the number of
+ * extents we accounted for is <= the amount we need for the new range
+ * then we can return, otherwise drop. Think of it like this
+ *
+ * [ 4k][MAX_SIZE]
+ *
+ * So we've grown the extent by a MAX_SIZE extent, this would mean we
+ * need 2 outstanding extents, on one side we have 1 and the other side
+ * we have 1 so they are == and we can return. But in this case
+ *
+ * [MAX_SIZE+4k][MAX_SIZE+4k]
+ *
+ * Each range on their own accounts for 2 extents, but merged together
+ * they are only 3 extents worth of accounting, so we need to drop in
+ * this case.
*/
+ old_size = other->end - other->start + 1;
num_extents = div64_u64(old_size + BTRFS_MAX_EXTENT_SIZE - 1,
BTRFS_MAX_EXTENT_SIZE);
+ old_size = new->end - new->start + 1;
+ num_extents += div64_u64(old_size + BTRFS_MAX_EXTENT_SIZE - 1,
+ BTRFS_MAX_EXTENT_SIZE);
+
if (div64_u64(new_size + BTRFS_MAX_EXTENT_SIZE - 1,
- BTRFS_MAX_EXTENT_SIZE) > num_extents)
+ BTRFS_MAX_EXTENT_SIZE) >= num_extents)
return;
spin_lock(&BTRFS_I(inode)->lock);
My patch to properly count outstanding extents wrt MAX_EXTENT_SIZE introduced a regression when joining two large areas. We need to take into account both sides of the merge to figure out if we're good with our current outstanding_extents count or if we need to drop it. For example if you merge two slightly larger than MAX_EXTENT size extents the accounting would incorrectly think we needed 4 outstanding extents when in fact we'd only need 3. Thanks, Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de> Signed-off-by: Josef Bacik <jbacik@fb.com> --- V1->V2: fixed another corner case where we join two large ranges fs/btrfs/inode.c | 31 ++++++++++++++++++++++++++----- 1 file changed, 26 insertions(+), 5 deletions(-)