On 15/05/2025 15:54, Darrick J. Wong wrote:
On Thu, May 15, 2025 at 09:16:12AM +0100, John Garry wrote:
On 14/05/2025 16:38, Darrick J. Wong wrote:
--- a/common/rc
+++ b/common/rc
@@ -2989,7 +2989,7 @@ _require_xfs_io_command()
fi
if [ "$param" == "-A" ]; then
opts+=" -d"
- pwrite_opts+="-D -V 1 -b 4k"
+ pwrite_opts+="-d -V 1 -b 4k"
according to the documentation for -b, 4096 is the default (so I don't think
that we need to set it explicitly). But is that flag even relevant to
pwritev2?
The documentation is wrong -- on XFS the default is the fs blocksize.
Everywhere else is 4k.
Right, I see that in init_cvtnum()
However, from checking write_buffer(), we seem to split writes on this
blocksize - that does not seem proper in this instance.
Should we really be doing something like:
xfs_io -d -C "pwrite -b $SIZE -V 1 -A -D 0 $SIZE" file
In _require_xfs_io_command? That only writes the first 4k of a file, so
matching buffer size is ok.
right, I missed that. The usage in _require_xfs_io_command looks ok.
Are you asking if _require_xfs_io_command should seek out the filesystem
block size, and use that for the buffer and write size arguments instead
of hardcoding 4k? For atomic writes, maybe it should be doing this,
since the fs blocksize could be 64k.
I was just a bit thrown by how we need to specify -b $size with -A to
actually write $size atomically.
Thanks,
John
