Funny, I had this problem (unbootable system, couldn't find net.mod even though it was there ls on the grub_rescue prompt didn't see it) with a XFS V4 partition, and rebuilding that as V5 and copying everything over seemed to have fixed it... but maybe I just got lucky on the first try. Interestingly, once I've got grub actually able to load normal.mod it doesn't seem to have problems finding any files on the V4 partition. For the sake of comparison here's are the full details of the two (lvm) volumes in question:
The partition that initially broke w/2.12~rc1-9: # xfs_db -r /dev/mapper/S-root xfs_db> version versionnum [0xb4b4+0xa] = V4,NLINK,DIRV2,ATTR,ALIGN,LOGV2,EXTFLG,MOREBITS,ATTR2,LAZYSBCOUNT # xfs_info /dev/mapper/S-root meta-data=/dev/mapper/S-root isize=256 agcount=4, agsize=524288 blks = sectsz=512 attr=2, projid32bit=0 = crc=0 finobt=0, sparse=0, rmapbt=0 = reflink=0 bigtime=0 inobtcount=0 nrext64=0 data = bsize=4096 blocks=2097152, imaxpct=25 = sunit=0 swidth=0 blks naming =version 2 bsize=4096 ascii-ci=0, ftype=0 log =internal log bsize=4096 blocks=2560, version=2 = sectsz=512 sunit=0 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0 And the partition that seems to be working OK (but maybe it's just luck?): # xfs_db -r /dev/mapper/S-root23 xfs_db> version versionnum [0xb4a5+0x18a] = V5,NLINK,DIRV2,ALIGN,LOGV2,EXTFLG,MOREBITS,ATTR2,LAZYSBCOUNT,PROJID32BIT,CRC,FTYPE,FINOBT,SPARSE_INODES,REFLINK,INOBTCNT,BIGTIME # xfs_info /dev/mapper/S-root23 meta-data=/dev/mapper/S-root23 isize=512 agcount=4, agsize=524288 blks = sectsz=512 attr=2, projid32bit=1 = crc=1 finobt=1, sparse=1, rmapbt=0 = reflink=1 bigtime=1 inobtcount=1 nrext64=0 data = bsize=4096 blocks=2097152, imaxpct=25 = sunit=0 swidth=0 blks naming =version 2 bsize=4096 ascii-ci=0, ftype=1 log =internal log bsize=4096 blocks=16384, version=2 = sectsz=512 sunit=0 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0 Do we know if the breakage related to bigtime feature? -- Jamie Heilman http://audible.transient.net/~jamie/