On Mon, Jan 04, 2016 at 02:12:18PM -0800, Darrick J. Wong wrote: > On Sun, Jan 03, 2016 at 04:15:25AM -0800, Christoph Hellwig wrote: > > On Sat, Dec 19, 2015 at 12:56:55AM -0800, Darrick J. Wong wrote: > > > Because struct xfs_agfl is 36 bytes long and has a 64-bit integer > > > inside it, gcc will quietly round the structure size up to the nearest > > > 64 bits -- in this case, 40 bytes. This results in the XFS_AGFL_SIZE > > > macro returning incorrect results for v5 filesystems on 64-bit > > > machines (118 items instead of 119). As a result, a 32-bit xfs_repair > > > will see garbage in AGFL item 119 and complain. > > > > > > Therefore, tell gcc not to pad the structure so that the AGFL size > > > calculation is correct. > > > > Do you have a testcase for this? > > Not much aside from: > > 0. Build kernel/xfsprogs with RFCv4 patches on a 64bit machine. > 1. Build kernel/xfsprogs with RFCv4 patches on a 32bit machine. > 2. Format a XFS with reflink and rmap on a 64-bit machine, so that the AGFL > size is maximized. > 3. Mount FS and create a reflinked file. > 4. Unmount and xfs_repair with the 32-bit build. > > I guess we could create a program that compares all the known sizeof(struct > xfs_disk_object) values against known good values and stuff that into the > xfsprogs build process. There's an xfstest for that: xfs/122. It notruns on my systems since the big xfsprogs build/header rework, and I haven't found the time to work out what it needs to run again. Also, I don't think it covers the AGFL structure, because that it relatively new and the test doesn't check any of the v5 specific structures.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
