Re: [PATCH v2 1/2] generic/020: adjust max_attrval_size for ceph

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On 6/9/22 10:21 PM, David Disseldorp wrote:
Hi Luís,

On Thu,  9 Jun 2022 11:53:42 +0100, Luís Henriques wrote:

CephFS doesn't have a maximum xattr size.  Instead, it imposes a maximum
size for the full set of xattrs names+values, which by default is 64K.

This patch fixes the max_attrval_size so that it is slightly < 64K in
order to accommodate any already existing xattrs in the file.

Signed-off-by: Luís Henriques <lhenriques@xxxxxxx>
---
  tests/generic/020 | 10 +++++++++-
  1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tests/generic/020 b/tests/generic/020
index d8648e96286e..76f13220fe85 100755
--- a/tests/generic/020
+++ b/tests/generic/020
@@ -128,7 +128,7 @@ _attr_get_max()
  	pvfs2)
  		max_attrval_size=8192
  		;;
-	xfs|udf|9p|ceph)
+	xfs|udf|9p)
  		max_attrval_size=65536
  		;;
  	bcachefs)
@@ -139,6 +139,14 @@ _attr_get_max()
  		# the underlying filesystem, so just use the lowest value above.
  		max_attrval_size=1024
  		;;
+	ceph)
+		# CephFS does not have a maximum value for attributes.  Instead,
+		# it imposes a maximum size for the full set of xattrs
+		# names+values, which by default is 64K.  Set this to a value
+		# that is slightly smaller than 64K so that it can accommodate
+		# already existing xattrs.
+		max_attrval_size=65000
+		;;
I take it a more exact calculation would be something like:
(64K - $max_attrval_namelen - sizeof(user.snrub="fish2\012"))?

Yeah, something like this looks better to me.

I am afraid without reaching up to the real max size we couldn't test the real bugs out from ceph. Such as the bug you fixed in ceph Locker.cc code.


Perhaps you could calculate this on the fly for CephFS by passing in the
filename and subtracting the `getfattr -d $filename` results... That
said, it'd probably get a bit ugly, expecially if encoding needs to be
taken into account.

Reviewed-by: David Disseldorp <ddiss@xxxxxxx>

Cheers, David





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