Commit 8baa9bcc authored by Nirjhar Roy (IBM)'s avatar Nirjhar Roy (IBM) Committed by Carlos Maiolino
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xfs: Fix xfs_last_rt_bmblock() 



Bug description:

If the size of the last rtgroup i.e, the rtg passed to
xfs_last_rt_bmblock() is such that the last rtextent falls in 0th word
offset of a bmblock of the bitmap file tracking this (last) rtgroup,
then in that case xfs_last_rt_bmblock() incorrectly returns the next
bmblock number instead of the current/last used bmblock number.
When xfs_last_rt_bmblock() incorrectly returns the next bmblock,
the loop to grow/modify the bmblocks in xfs_growfs_rtg() doesn't
execute and xfs_growfs basically does a nop in certain cases.

xfs_growfs will do a nop when the new size of the fs will have the same
number of rtgroups i.e, we are only growing the last rtgroup.

Reproduce:
$ mkfs.xfs -m metadir=0 -r rtdev=/dev/loop1 /dev/loop0 \
	-r size=32769b -f
$ mount -o rtdev=/dev/loop1 /dev/loop0 /mnt/scratch
$ xfs_growfs -R $(( 32769 + 1 )) /mnt/scratch
$ xfs_info /mnt/scratch | grep rtextents
$ # We can see that rtextents hasn't changed

Fix:
Fix this by returning the current/last used bmblock when the last
rtgroup size is not a multiple xfs_rtbitmap_rtx_per_rbmblock()
and the next bmblock when the rtgroup size is a multiple of
xfs_rtbitmap_rtx_per_rbmblock() i.e, the existing blocks are
completely used up.
Also, I have renamed xfs_last_rt_bmblock() to
xfs_last_rt_bmblock_to_extend() to signify that this function
returns the bmblock number to extend and NOT always the last used
bmblock number.

Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Signed-off-by: default avatarNirjhar Roy (IBM) <nirjhar.roy.lists@gmail.com>
Signed-off-by: default avatarCarlos Maiolino <cem@kernel.org>
parent 115ea07b

fs/xfs/xfs_rtalloc.c

+24 −6
Original line number Diff line number Diff line
@@ -1082,17 +1082,27 @@ xfs_last_rtgroup_extents( 
}



/*

 * Calculate the last rbmblock currently used.

 * This will return the bitmap block number (indexed at 0) that will be

 * extended/modified. There are 2 cases here:

 * 1. The size of the rtg is such that it is a multiple of

 *    xfs_rtbitmap_rtx_per_rbmblock() i.e, an integral number of bitmap blocks

 *    are completely filled up. In this case, we should return

 *    1 + (the last used bitmap block number).

 * 2. The size of the rtg is not an multiple of xfs_rtbitmap_rtx_per_rbmblock().

 *    Here we will return the block number of last used block number. In this

 *    case, we will modify the last used bitmap block to extend the size of the

 *    rtgroup.

 *

 * This also deals with the case where there were no rtextents before.

 */

static xfs_fileoff_t

xfs_last_rt_bmblock(

xfs_last_rt_bmblock_to_extend(

	struct xfs_rtgroup	*rtg)

{

	struct xfs_mount	*mp = rtg_mount(rtg);

	xfs_rgnumber_t		rgno = rtg_rgno(rtg);

	xfs_fileoff_t		bmbno = 0;

	unsigned int		mod = 0;



	ASSERT(!mp->m_sb.sb_rgcount || rgno >= mp->m_sb.sb_rgcount - 1);
@@ -1100,9 +1110,16 @@ xfs_last_rt_bmblock( 
		xfs_rtxnum_t	nrext = xfs_last_rtgroup_extents(mp);



		/* Also fill up the previous block if not entirely full. */

		bmbno = xfs_rtbitmap_blockcount_len(mp, nrext);

		if (xfs_rtx_to_rbmword(mp, nrext) != 0)

			bmbno--;

		/* We are doing a -1 to convert it to a 0 based index */

		bmbno = xfs_rtbitmap_blockcount_len(mp, nrext) - 1;

		div_u64_rem(nrext, xfs_rtbitmap_rtx_per_rbmblock(mp), &mod);

		/*

		 * mod = 0 means that all the current blocks are full. So

		 * return the next block number to be used for the rtgroup

		 * growth.

		 */

		if (mod == 0)

			bmbno++;

	}



	return bmbno;
@@ -1207,7 +1224,8 @@ xfs_growfs_rtg( 
			goto out_rele;

	}



	for (bmbno = xfs_last_rt_bmblock(rtg); bmbno < bmblocks; bmbno++) {

	for (bmbno = xfs_last_rt_bmblock_to_extend(rtg); bmbno < bmblocks;

			bmbno++) {

		error = xfs_growfs_rt_bmblock(rtg, nrblocks, rextsize, bmbno);

		if (error)

			goto out_error;