[PATCH 0/1] generic/103: increase reserved bytes for bcachefs

[PATCH 0/1] generic/103: increase reserved bytes for bcachefs

[Dan Robertson]

After some testing it seems that generic/103 fails intermittently due to
a split leaf that can be hit in fallocate. Since the bcachefs node sizes
are larger on bcachefs than some other filesystems the reserved size
needs to be bumped up a bit when FSTYP is bcachefs.

On a system that generic/103 failed semi-regularly on, I can now it
in a loop without hitting a failure.

Dan Robertson (1):
  generic/103: increase reserved bytes for bcachefs

 tests/generic/103 | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

[PATCH 1/1] generic/103: increase reserved bytes for bcachefs

[Dan Robertson]

The bcachefs btree nodes are quite large. If we only reserve 512 bytes
we hit an intermittent failure where the fallocate that is intented to
fill the available space triggers a btree node split and the exente update
is interrupted. The retry of the extent update will fail because the
new amount of available space is less than that of the request.

Signed-off-by: Dan Robertson <dan@dlrobertson.com>
---
 tests/generic/103 | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tests/generic/103 b/tests/generic/103
index b22b0159..610f31f6 100755
--- a/tests/generic/103
+++ b/tests/generic/103
@@ -43,7 +43,15 @@ _consume_freesp()
 
 	# consume nearly all available space (leave ~512kB)
 	avail=`_get_available_space $SCRATCH_MNT`
-	filesizekb=$((avail / 1024 - 512))
+	if [ $FSTYP = "bcachefs" ]; then
+		# The bcachefs btree nodes are quite large. If the fallocate
+		# triggers a split leaf of a btree node, we'll need more
+		# than 512 kept in reserve.
+		reserve=1024
+	else
+		reserve=512
+	fi
+	filesizekb=$((avail / 1024 - reserve))
 	$XFS_IO_PROG -fc "falloc 0 ${filesizekb}k" $file
 }
 

Re: [PATCH 1/1] generic/103: increase reserved bytes for bcachefs

[Kent Overstreet]

On Thu, Jun 24, 2021 at 10:11:18PM -0400, Dan Robertson wrote:
> The bcachefs btree nodes are quite large. If we only reserve 512 bytes
> we hit an intermittent failure where the fallocate that is intented to
> fill the available space triggers a btree node split and the exente update
> is interrupted. The retry of the extent update will fail because the
> new amount of available space is less than that of the request.
> 
> Signed-off-by: Dan Robertson <dan@dlrobertson.com>

Thanks, merged