On Thu, Jul 06, 2017 at 03:47:38PM -0700, Darrick J. Wong wrote: > Heh, > > Brian Foster complained that he could create filesystems that do this on > for-next during the first mount attempt: > > [62548.735187] XFS (dm-1): Log size 4497 blocks too small, minimum size is 4499 blocks > [62548.742853] XFS (dm-1): AAIEEE! Log failed size checks. Abort! > > I started looking into why mkfs and mount have different ideas about the > minimum log length, and discovered that the struct xfs_trans_res between > kernel and userspace have vastly different ideas about how much space a > transaction type requires. Most of the problems are easily fixed by > constructing a more complete phony superblock in mkfs' max_trans_res() > (patches soon), but I ran into a nasty one that I cannot resolve in > tr_symlink. > > In fs/xfs/, MAXPATHLEN is defined as 1024, and returns -ENAMETOOLONG > (set) or -EFSCORRUPTED (get) if it is fed a symlink with a target longer > than 1024 bytes. > > However, xfsprogs picks up the definition offered by libc, which is > PATH_MAX (4096). Unfortunately, this also means that xfs_repair only > complains if the target is longer than 4096 bytes. > > AFAICT the other filesystems allow 4k symlink targets, but XFS' special > definition has been there at least since git-prehistory. > > Soooo... which is the correct value? We could raise the kernel limit to > 4k with at least the obvious problem that old kernels can't read such > symlinks, or lower the xfsprogs limit to 1k, with the problem that at > least in theory this would result in xfs_repair flagging things it > wouldn't have before. > > My cautious side says lower xfsprogs, but I'll ask the list anyway. :) A summary of what we just talked about on IRC - it's part of the on disk format so grabbing an arbitrary value from libc is wrong. Rename the kernel definition to XFS_SYMLINK_MAXLEN and move to xfs_format.h, make all the userspace and kernel code use the new libxfs definition.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
