Commit 074e427b authored by Dave Chinner's avatar Dave Chinner Committed by Dave Chinner
Browse files

xfs: sanitise sb_bad_features2 handling 



We currently have to ensure that every time we update sb_features2
that we update sb_bad_features2. Now that we log and format the
superblock in it's entirety we actually don't have to care because
we can simply update the sb_bad_features2 when we format it into the
buffer. This removes the need for anything but the mount and
superblock formatting code to care about sb_bad_features2, and
hence removes the possibility that we forget to update bad_features2
when necessary in the future.

Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarBrian Foster <bfoster@redhat.com>
Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
parent 61e63ecb

fs/xfs/libxfs/xfs_format.h

+7 −7
Original line number Diff line number Diff line
@@ -151,10 +151,13 @@ typedef struct xfs_sb { 
	__uint32_t	sb_features2;	/* additional feature bits */



	/*

	 * bad features2 field as a result of failing to pad the sb

	 * structure to 64 bits. Some machines will be using this field

	 * for features2 bits. Easiest just to mark it bad and not use

	 * it for anything else.

	 * bad features2 field as a result of failing to pad the sb structure to

	 * 64 bits. Some machines will be using this field for features2 bits.

	 * Easiest just to mark it bad and not use it for anything else.

	 *

	 * This is not kept up to date in memory; it is always overwritten by

	 * the value in sb_features2 when formatting the incore superblock to

	 * the disk buffer.

	 */

	__uint32_t	sb_bad_features2;
@@ -453,13 +456,11 @@ static inline void xfs_sb_version_addattr2(struct xfs_sb *sbp) 
{

	sbp->sb_versionnum |= XFS_SB_VERSION_MOREBITSBIT;

	sbp->sb_features2 |= XFS_SB_VERSION2_ATTR2BIT;

	sbp->sb_bad_features2 |= XFS_SB_VERSION2_ATTR2BIT;

}



static inline void xfs_sb_version_removeattr2(struct xfs_sb *sbp)

{

	sbp->sb_features2 &= ~XFS_SB_VERSION2_ATTR2BIT;

	sbp->sb_bad_features2 &= ~XFS_SB_VERSION2_ATTR2BIT;

	if (!sbp->sb_features2)

		sbp->sb_versionnum &= ~XFS_SB_VERSION_MOREBITSBIT;

}
@@ -475,7 +476,6 @@ static inline void xfs_sb_version_addprojid32bit(struct xfs_sb *sbp) 
{

	sbp->sb_versionnum |= XFS_SB_VERSION_MOREBITSBIT;

	sbp->sb_features2 |= XFS_SB_VERSION2_PROJID32BIT;

	sbp->sb_bad_features2 |= XFS_SB_VERSION2_PROJID32BIT;

}



/*

fs/xfs/libxfs/xfs_sb.c

+7 −1
Original line number Diff line number Diff line
@@ -497,7 +497,6 @@ xfs_sb_to_disk( 
	to->sb_fdblocks = cpu_to_be64(from->sb_fdblocks);

	to->sb_frextents = cpu_to_be64(from->sb_frextents);





	to->sb_flags = from->sb_flags;

	to->sb_shared_vn = from->sb_shared_vn;

	to->sb_inoalignmt = cpu_to_be32(from->sb_inoalignmt);
@@ -507,6 +506,13 @@ xfs_sb_to_disk( 
	to->sb_logsectlog = from->sb_logsectlog;

	to->sb_logsectsize = cpu_to_be16(from->sb_logsectsize);

	to->sb_logsunit = cpu_to_be32(from->sb_logsunit);



	/*

	 * We need to ensure that bad_features2 always matches features2.

	 * Hence we enforce that here rather than having to remember to do it

	 * everywhere else that updates features2.

	 */

	from->sb_bad_features2 = from->sb_features2;

	to->sb_features2 = cpu_to_be32(from->sb_features2);

	to->sb_bad_features2 = cpu_to_be32(from->sb_bad_features2);

fs/xfs/xfs_mount.c

+11 −12
Original line number Diff line number Diff line
@@ -640,25 +640,24 @@ xfs_mountfs( 
	xfs_sb_mount_common(mp, sbp);



	/*

	 * 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.

	 * 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.

	 *

	 * 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 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. The

	 * superblock writeback code ensures the new sb_features2 is copied to

	 * sb_bad_features2 before it is logged or written to disk.

	 */

	if (xfs_sb_has_mismatched_features2(sbp)) {

		xfs_warn(mp, "correcting sb_features alignment problem");

		sbp->sb_features2 |= sbp->sb_bad_features2;

		sbp->sb_bad_features2 = sbp->sb_features2;

		mp->m_update_sb = true;



		/*

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