Commit ced10f24 authored by Long Li's avatar Long Li
Browse files

xfs: simplify extent allocation alignment 

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I9VTE3


CVE: NA

--------------------------------

We currently align extent allocation to stripe unit or stripe width.
That is specified by an external parameter to the allocation code,
which then manipulates the xfs_alloc_args alignment configuration in
interesting ways.

The args->alignment field specifies extent start alignment, but
because we may be attempting non-aligned allocation first there are
also slop variables that allow for those allocation attempts to
account for aligned allocation if they fail.

This gets much more complex as we introduce forced allocation
alignment, where extent size hints are used to generate the extent
start alignment. extent size hints currently only affect extent
lengths (via args->prod and args->mod) and so with this change we
will have two different start alignment conditions.

Avoid this complexity by always using args->alignment to indicate
extent start alignment, and always using args->prod/mod to indicate
extent length adjustment.

Fixes: 63f4d844 ("fs: xfs: Make file data allocations observe the 'forcealign' flag")
Signed-off-by: default avatarLong Li <leo.lilong@huawei.com>
parent 7f9d8a74

fs/xfs/libxfs/xfs_bmap.c

+27 −51
Original line number Diff line number Diff line
@@ -3262,6 +3262,10 @@ xfs_bmap_select_minlen( 
{

	xfs_extlen_t nlen = 0;



	/* Adjust best length for extent start alignment. */

	if (*blen > args->alignment)

		*blen -= args->alignment;



	if (notinit || *blen < ap->minlen) {

		/*

		 * Since we did a BUF_TRYLOCK above, it is possible that
@@ -3436,9 +3440,8 @@ xfs_bmap_btalloc( 
	xfs_fileoff_t	orig_offset;

	xfs_extlen_t	orig_length;

	xfs_extlen_t	blen;

	xfs_extlen_t	nextminlen = 0;

	xfs_extlen_t    alignment;

	int		nullfb;		/* true if ap->firstblock isn't set */

	int		isaligned;

	int		tryagain;

	int		error;

	int		stripe_align;
@@ -3497,7 +3500,7 @@ xfs_bmap_btalloc( 
	/*

	 * Normal allocation, done through xfs_alloc_vextent.

	 */

	tryagain = isaligned = 0;

	tryagain = 0;

	memset(&args, 0, sizeof(args));

	args.tp = ap->tp;

	args.mp = mp;
@@ -3508,13 +3511,12 @@ xfs_bmap_btalloc( 
	 * xfs_get_cowextsz_hint() returns extsz_hint for when forcealign is

	 * set as forcealign and cowextsz_hint are mutually exclusive

	 */

	if (xfs_inode_forcealign(ap->ip) && align) {

	if (xfs_inode_forcealign(ap->ip))

		args.alignment = align;

		if (stripe_align == 0 || stripe_align % align)

			stripe_align = align;

	} else {

	else if (stripe_align)

		args.alignment = stripe_align;

	else

		args.alignment = 1;

	}



	/* Trim the allocation back to the maximum an AG can fit. */

	args.maxlen = min(ap->length, mp->m_ag_max_usable);
@@ -3571,44 +3573,21 @@ xfs_bmap_btalloc( 
			args.fsbno = NULLFSBLOCK;

			goto alloc_out;

		}

	} else if (ap->aeof) {

		if (!ap->offset) {

			args.alignment = stripe_align;

			atype = args.type;

			isaligned = 1;

			/*

			 * Adjust minlen to try and preserve alignment if we

			 * can't guarantee an aligned maxlen extent.

			 */

			if (blen > args.alignment &&

			    blen <= args.maxlen + args.alignment)

				args.minlen = blen - args.alignment;

		} else {

		args.alignment = 1;

	} else if (ap->aeof && ap->offset) {

		/*

		 * First try an exact bno allocation.

		 * If it fails then do a near or start bno

		 * allocation with alignment turned on.

		 */

		alignment = args.alignment;

		atype = args.type;

		tryagain = 1;

		args.type = XFS_ALLOCTYPE_THIS_BNO;

			/*

			 * Compute the minlen+alignment for the

			 * next case.  Set slop so that the value

			 * of minlen+alignment+slop doesn't go up

			 * between the calls.

			 */

			if (blen > stripe_align && blen <= args.maxlen)

				nextminlen = blen - stripe_align;

			else

				nextminlen = args.minlen;

			if (nextminlen + stripe_align > args.minlen + 1)

				args.minalignslop =

					nextminlen + stripe_align -

					args.minlen - 1;

			else

				args.minalignslop = 0;

		}

		args.fsbno = ap->blkno;



		args.alignment = 1;

		args.minalignslop = alignment - args.alignment;

	}

	args.postallocs = 1;

	args.minleft = ap->minleft;
@@ -3627,10 +3606,8 @@ xfs_bmap_btalloc( 
		 */

		args.type = atype;

		args.fsbno = ap->blkno;

		args.alignment = stripe_align;

		args.minlen = nextminlen;

		args.alignment = alignment;

		args.minalignslop = 0;

		isaligned = 1;

		if ((error = xfs_alloc_vextent(&args)))

			return error;

	}
@@ -3644,12 +3621,11 @@ xfs_bmap_btalloc( 
		goto alloc_out;

	}



	if (isaligned && args.fsbno == NULLFSBLOCK) {

	if (args.alignment > 1 && args.fsbno == NULLFSBLOCK) {

		/*

		 * allocation failed, so turn off alignment and

		 * try again.

		 */

		args.type = atype;

		args.fsbno = ap->blkno;

		args.alignment = 0;

		if ((error = xfs_alloc_vextent(&args)))