Commit e6957ea4 authored by Eric Sandeen's avatar Eric Sandeen Committed by Lachlan McIlroy
Browse files

[XFS] Ensure "both" features2 slots are consistent 



Since older kernels may look in the sb_bad_features2 slot for flags,
rather than zeroing it out on fixup, we should make it equal to the
sb_features2 value.

Also, if the ATTR2 flag was not found prior to features2 fixup, it was not
set in the mount flags, so re-check after the fixup so that the current
session will use the feature.

Also fix up the comments to reflect these changes.

SGI-PV: 980085
SGI-Modid: xfs-linux-melb:xfs-kern:30778a

Signed-off-by: default avatarEric Sandeen <sandeen@sandeen.net>
Signed-off-by: default avatarDavid Chinner <dgc@sgi.com>
Signed-off-by: default avatarLachlan McIlroy <lachlan@sgi.com>
parent ee1c0908

fs/xfs/xfs_mount.c

+25 −12
Original line number Diff line number Diff line
@@ -972,23 +972,35 @@ xfs_mountfs( 
	xfs_mount_common(mp, sbp);



	/*

	 * Check for a bad features2 field alignment. This happened on

	 * some platforms due to xfs_sb_t not being 64bit size aligned

	 * when sb_features was added and hence the compiler put it in

	 * the wrong place.

	 * Check for a mismatched features2 values.  Older kernels

	 * read & wrote into the wrong sb offset for sb_features2

	 * on some platforms due to xfs_sb_t not being 64bit size aligned

	 * when sb_features2 was added, which made older superblock

	 * reading/writing routines swap it as a 64-bit value.

	 *

	 * If we detect a bad field, we or the set bits into the existing

	 * features2 field in case it has already been modified and we

	 * don't want to lose any features. Zero the bad one and mark

	 * the two fields as needing updates once the transaction subsystem

	 * is online.

	 */

	if (xfs_sb_has_bad_features2(sbp)) {

	 * For backwards compatibility, we make both slots equal.

	 *

	 * If we detect a mismatched field, we OR the set bits into the

	 * existing features2 field in case it has already been modified; we

	 * don't want to lose any features.  We then update the bad location

	 * with the ORed value so that older kernels will see any features2

	 * flags, and mark the two fields as needing updates once the

	 * transaction subsystem is online.

	 */

	if (xfs_sb_has_mismatched_features2(sbp)) {

		cmn_err(CE_WARN,

			"XFS: correcting sb_features alignment problem");

		sbp->sb_features2 |= sbp->sb_bad_features2;

		sbp->sb_bad_features2 = 0;

		sbp->sb_bad_features2 = sbp->sb_features2;

		update_flags |= XFS_SB_FEATURES2 | XFS_SB_BAD_FEATURES2;



		/*

		 * Re-check for ATTR2 in case it was found in bad_features2

		 * slot.

		 */

		if (xfs_sb_version_hasattr2(&mp->m_sb))

			mp->m_flags |= XFS_MOUNT_ATTR2;



	}



	/*
@@ -1896,7 +1908,8 @@ xfs_uuid_unmount( 


/*

 * Used to log changes to the superblock unit and width fields which could

 * be altered by the mount options. Only the first superblock is updated.

 * be altered by the mount options, as well as any potential sb_features2

 * fixup. Only the first superblock is updated.

 */

STATIC void

xfs_mount_log_sb(

fs/xfs/xfs_sb.h

+4 −3
Original line number Diff line number Diff line
@@ -320,11 +320,12 @@ static inline int xfs_sb_good_version(xfs_sb_t *sbp) 
#endif /* __KERNEL__ */



/*

 * Detect a bad features2 field

 * Detect a mismatched features2 field.  Older kernels read/wrote

 * this into the wrong slot, so to be safe we keep them in sync.

 */

static inline int xfs_sb_has_bad_features2(xfs_sb_t *sbp)

static inline int xfs_sb_has_mismatched_features2(xfs_sb_t *sbp)

{

	return (sbp->sb_bad_features2 != 0);

	return (sbp->sb_bad_features2 != sbp->sb_features2);

}



static inline unsigned xfs_sb_version_tonew(unsigned v)

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