mkfs.xfs ... lazy-count=1 ... not mountable by older kernels?
Hi all,
Is it expected that filesystems made with lazy-count=1 are not mountable by older kernels?
I'm installing a system based with install media based on 2.6.19 and mkfs.xfs 2.8.11 (its Gentoo 2007.0). That mkfs.xfs is old so i copied over a 2.9.4 binary and used that to mkfs the filesystem but its unmountable. Removing the lazy-count=1 option makes it mountable.
Is this an expected incompatibility or is mix-n-matching xfsprogs a bad idea?
Thanks!
Quoted 4 lines · David Sparks
Hi all,
Is it expected that filesystems made with lazy-count=1 are not mountable by older kernels?
That is expected. lazy-count is a mkfs option because it changes the on-disk format slightly, and older kernels do not understand that format. Hence mkfs sets a superblock feature bit to prevent the filesystem from being mounted on kernels that don't understand the slightly different disk format.
Cheers,
Dave.
Signature · 3 lines
Dave Chinner Principal Engineer SGI Australian Software Group
Quoted 6 lines · David Chinner
Quoted 4 lines · David Sparks
Hi all,
Is it expected that filesystems made with lazy-count=1 are not mountable by older kernels?
Quoted 8 lines
That is expected. lazy-count is a mkfs option because it changes the on-disk format slightly, and older kernels do not understand that format. Hence mkfs sets a superblock feature bit to prevent the filesystem from being mounted on kernels that don't understand the slightly different disk format.
Cheers,
Dave.
And there will be a message in the logs but it probably isn't overly obvious what it is talking about.
Looking at code, I presume it will come from:
if (!XFS_SB_GOOD_VERSION(sbp)) {
xfs_fs_mount_cmn_err(flags, "bad version");
return XFS_ERROR(EWRONGFS);
}so there will be a msg about a "bad version".
--Tim
Quoted 19 lines · Timothy Shimmin
Quoted 6 lines · David Chinner
Quoted 4 lines · David Sparks
Hi all,
Is it expected that filesystems made with lazy-count=1 are not mountable by older kernels?
Quoted 8 lines
That is expected. lazy-count is a mkfs option because it changes the on-disk format slightly, and older kernels do not understand that format. Hence mkfs sets a superblock feature bit to prevent the filesystem from being mounted on kernels that don't understand the slightly different disk format.
Cheers,
Dave.
And there will be a message in the logs but it probably isn't overly obvious what it is talking about.
Quoted 10 lines
Looking at code, I presume it will come from:
if (!XFS_SB_GOOD_VERSION(sbp)) { xfs_fs_mount_cmn_err(flags, "bad version"); return XFS_ERROR(EWRONGFS); }so there will be a msg about a "bad version".
--Tim
Has anyone done any benchmarks with Dave Chinner's recommendations for mkfs.xfs/optmizations?
Justin.