xfs: split xfs_bmap_btalloc

Split out the nullfb case into a separate function to reduce the stack
footprint and make the code more readable.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Alex Elder <aelder@sgi.com>

fs/xfs/xfs_bmap.c

@@ -2550,106 +2550,56 @@ xfs_bmap_rtalloc(
 }
 
 STATIC int
-xfs_bmap_btalloc(
-	xfs_bmalloca_t	*ap)		/* bmap alloc argument struct */
+xfs_bmap_btalloc_nullfb(
+	struct xfs_bmalloca	*ap,
+	struct xfs_alloc_arg	*args,
+	xfs_extlen_t		*blen)
 {
-	xfs_mount_t	*mp;		/* mount point structure */
-	xfs_alloctype_t	atype = 0;	/* type for allocation routines */
-	xfs_extlen_t	align;		/* minimum allocation alignment */
-	xfs_agnumber_t	ag;
-	xfs_agnumber_t	fb_agno;	/* ag number of ap->firstblock */
-	xfs_agnumber_t	startag;
-	xfs_alloc_arg_t	args;
-	xfs_extlen_t	blen;
-	xfs_extlen_t	nextminlen = 0;
-	xfs_perag_t	*pag;
-	int		nullfb;		/* true if ap->firstblock isn't set */
-	int		isaligned;
-	int		notinit;
-	int		tryagain;
+	struct xfs_mount	*mp = ap->ip->i_mount;
+	struct xfs_perag	*pag;
+	xfs_agnumber_t		ag, startag;
+	int			notinit = 0;
 	int			error;
 
-	mp = ap->ip->i_mount;
-	align = ap->userdata ? xfs_get_extsz_hint(ap->ip) : 0;
-	if (unlikely(align)) {
-		error = xfs_bmap_extsize_align(mp, ap->gotp, ap->prevp,
-						align, 0, ap->eof, 0, ap->conv,
-						&ap->off, &ap->alen);
-		ASSERT(!error);
-		ASSERT(ap->alen);
-	}
-	nullfb = ap->firstblock == NULLFSBLOCK;
-	fb_agno = nullfb ? NULLAGNUMBER : XFS_FSB_TO_AGNO(mp, ap->firstblock);
-	if (nullfb) {
-		if (ap->userdata && xfs_inode_is_filestream(ap->ip)) {
-			ag = xfs_filestream_lookup_ag(ap->ip);
-			ag = (ag != NULLAGNUMBER) ? ag : 0;
-			ap->rval = XFS_AGB_TO_FSB(mp, ag, 0);
-		} else {
-			ap->rval = XFS_INO_TO_FSB(mp, ap->ip->i_ino);
-		}
-	} else
-		ap->rval = ap->firstblock;
-
-	xfs_bmap_adjacent(ap);
-
-	/*
-	 * If allowed, use ap->rval; otherwise must use firstblock since
-	 * it's in the right allocation group.
-	 */
-	if (nullfb || XFS_FSB_TO_AGNO(mp, ap->rval) == fb_agno)
-		;
-	else
-		ap->rval = ap->firstblock;
-	/*
-	 * Normal allocation, done through xfs_alloc_vextent.
-	 */
-	tryagain = isaligned = 0;
-	args.tp = ap->tp;
-	args.mp = mp;
-	args.fsbno = ap->rval;
-	args.maxlen = MIN(ap->alen, mp->m_sb.sb_agblocks);
-	args.firstblock = ap->firstblock;
-	blen = 0;
-	if (nullfb) {
 	if (ap->userdata && xfs_inode_is_filestream(ap->ip))
-			args.type = XFS_ALLOCTYPE_NEAR_BNO;
+		args->type = XFS_ALLOCTYPE_NEAR_BNO;
 	else
-			args.type = XFS_ALLOCTYPE_START_BNO;
-		args.total = ap->total;
+		args->type = XFS_ALLOCTYPE_START_BNO;
+	args->total = ap->total;
 
 	/*
-		 * Search for an allocation group with a single extent
-		 * large enough for the request.
-		 *
-		 * If one isn't found, then adjust the minimum allocation
-		 * size to the largest space found.
+	 * Search for an allocation group with a single extent large enough
+	 * for the request.  If one isn't found, then adjust the minimum
+	 * allocation size to the largest space found.
 	 */
-		startag = ag = XFS_FSB_TO_AGNO(mp, args.fsbno);
+	startag = ag = XFS_FSB_TO_AGNO(mp, args->fsbno);
 	if (startag == NULLAGNUMBER)
 		startag = ag = 0;
-		notinit = 0;
+
 	pag = xfs_perag_get(mp, ag);
-		while (blen < ap->alen) {
-			if (!pag->pagf_init &&
-			    (error = xfs_alloc_pagf_init(mp, args.tp,
-				    ag, XFS_ALLOC_FLAG_TRYLOCK))) {
+	while (*blen < ap->alen) {
+		if (!pag->pagf_init) {
+			error = xfs_alloc_pagf_init(mp, args->tp, ag,
+						    XFS_ALLOC_FLAG_TRYLOCK);
+			if (error) {
 				xfs_perag_put(pag);
 				return error;
 			}
+		}
+
 		/*
 		 * See xfs_alloc_fix_freelist...
 		 */
 		if (pag->pagf_init) {
 			xfs_extlen_t	longest;
 			longest = xfs_alloc_longest_free_extent(mp, pag);
-				if (blen < longest)
-					blen = longest;
+			if (*blen < longest)
+				*blen = longest;
 		} else
 			notinit = 1;
 
 		if (xfs_inode_is_filestream(ap->ip)) {
-				if (blen >= ap->alen)
+			if (*blen >= ap->alen)
 				break;
 
 			if (ap->userdata) {
@@ -2684,31 +2634,99 @@ xfs_bmap_btalloc(
 		pag = xfs_perag_get(mp, ag);
 	}
 	xfs_perag_put(pag);
+
 	/*
 	 * Since the above loop did a BUF_TRYLOCK, it is
 	 * possible that there is space for this request.
 	 */
-		if (notinit || blen < ap->minlen)
-			args.minlen = ap->minlen;
+	if (notinit || *blen < ap->minlen)
+		args->minlen = ap->minlen;
 	/*
 	 * If the best seen length is less than the request
 	 * length, use the best as the minimum.
 	 */
-		else if (blen < ap->alen)
-			args.minlen = blen;
+	else if (*blen < ap->alen)
+		args->minlen = *blen;
 	/*
 	 * Otherwise we've seen an extent as big as alen,
 	 * use that as the minimum.
 	 */
 	else
-			args.minlen = ap->alen;
+		args->minlen = ap->alen;
 
 	/*
 	 * set the failure fallback case to look in the selected
 	 * AG as the stream may have moved.
 	 */
 	if (xfs_inode_is_filestream(ap->ip))
-			ap->rval = args.fsbno = XFS_AGB_TO_FSB(mp, ag, 0);
+		ap->rval = args->fsbno = XFS_AGB_TO_FSB(mp, ag, 0);
+
+	return 0;
+}
+
+STATIC int
+xfs_bmap_btalloc(
+	xfs_bmalloca_t	*ap)		/* bmap alloc argument struct */
+{
+	xfs_mount_t	*mp;		/* mount point structure */
+	xfs_alloctype_t	atype = 0;	/* type for allocation routines */
+	xfs_extlen_t	align;		/* minimum allocation alignment */
+	xfs_agnumber_t	fb_agno;	/* ag number of ap->firstblock */
+	xfs_agnumber_t	ag;
+	xfs_alloc_arg_t	args;
+	xfs_extlen_t	blen;
+	xfs_extlen_t	nextminlen = 0;
+	int		nullfb;		/* true if ap->firstblock isn't set */
+	int		isaligned;
+	int		tryagain;
+	int		error;
+
+	mp = ap->ip->i_mount;
+	align = ap->userdata ? xfs_get_extsz_hint(ap->ip) : 0;
+	if (unlikely(align)) {
+		error = xfs_bmap_extsize_align(mp, ap->gotp, ap->prevp,
+						align, 0, ap->eof, 0, ap->conv,
+						&ap->off, &ap->alen);
+		ASSERT(!error);
+		ASSERT(ap->alen);
+	}
+	nullfb = ap->firstblock == NULLFSBLOCK;
+	fb_agno = nullfb ? NULLAGNUMBER : XFS_FSB_TO_AGNO(mp, ap->firstblock);
+	if (nullfb) {
+		if (ap->userdata && xfs_inode_is_filestream(ap->ip)) {
+			ag = xfs_filestream_lookup_ag(ap->ip);
+			ag = (ag != NULLAGNUMBER) ? ag : 0;
+			ap->rval = XFS_AGB_TO_FSB(mp, ag, 0);
+		} else {
+			ap->rval = XFS_INO_TO_FSB(mp, ap->ip->i_ino);
+		}
+	} else
+		ap->rval = ap->firstblock;
+
+	xfs_bmap_adjacent(ap);
+
+	/*
+	 * If allowed, use ap->rval; otherwise must use firstblock since
+	 * it's in the right allocation group.
+	 */
+	if (nullfb || XFS_FSB_TO_AGNO(mp, ap->rval) == fb_agno)
+		;
+	else
+		ap->rval = ap->firstblock;
+	/*
+	 * Normal allocation, done through xfs_alloc_vextent.
+	 */
+	tryagain = isaligned = 0;
+	args.tp = ap->tp;
+	args.mp = mp;
+	args.fsbno = ap->rval;
+	args.maxlen = MIN(ap->alen, mp->m_sb.sb_agblocks);
+	args.firstblock = ap->firstblock;
+	blen = 0;
+	if (nullfb) {
+		error = xfs_bmap_btalloc_nullfb(ap, &args, &blen);
+		if (error)
+			return error;
 	} else if (ap->low) {
 		if (xfs_inode_is_filestream(ap->ip))
 			args.type = XFS_ALLOCTYPE_FIRST_AG;