[XFS] Reduce stack usage within xfs_bmapi by rearranging some code,

splitting realtime/btree allocators apart.  Based on Glens original
patches.

SGI-PV: 947312
SGI-Modid: xfs-linux-melb:xfs-kern:25372a
Signed-off-by: Nathan Scott <nathans@sgi.com>

fs/xfs/xfs_bmap.c

@@ -2294,25 +2294,15 @@ xfs_bmap_extsize_align(
 
 #define XFS_ALLOC_GAP_UNITS	4
 
-/*
- * xfs_bmap_alloc is called by xfs_bmapi to allocate an extent for a file.
- * It figures out where to ask the underlying allocator to put the new extent.
- */
 STATIC int
-xfs_bmap_alloc(
+xfs_bmap_adjacent(
 	xfs_bmalloca_t	*ap)		/* bmap alloc argument struct */
 {
 	xfs_fsblock_t	adjust;		/* adjustment to block numbers */
-	xfs_alloctype_t	atype=0;	/* type for allocation routines */
-	int		error;		/* error return value */
 	xfs_agnumber_t	fb_agno;	/* ag number of ap->firstblock */
 	xfs_mount_t	*mp;		/* mount point structure */
 	int		nullfb;		/* true if ap->firstblock isn't set */
 	int		rt;		/* true if inode is realtime */
-	xfs_extlen_t	prod = 0;	/* product factor for allocators */
-	xfs_extlen_t	ralen = 0;	/* realtime allocation length */
-	xfs_extlen_t	align;		/* minimum allocation alignment */
-	xfs_rtblock_t	rtx;
 
 #define	ISVALID(x,y)	\
 	(rt ? \
@@ -2321,75 +2311,10 @@ xfs_bmap_alloc(
 		XFS_FSB_TO_AGNO(mp, x) < mp->m_sb.sb_agcount && \
 		XFS_FSB_TO_AGBNO(mp, x) < mp->m_sb.sb_agblocks)
 
-	/*
-	 * Set up variables.
-	 */
 	mp = ap->ip->i_mount;
 	nullfb = ap->firstblock == NULLFSBLOCK;
 	rt = XFS_IS_REALTIME_INODE(ap->ip) && ap->userdata;
 	fb_agno = nullfb ? NULLAGNUMBER : XFS_FSB_TO_AGNO(mp, ap->firstblock);
-	if (rt) {
-		align = ap->ip->i_d.di_extsize ?
-			ap->ip->i_d.di_extsize : mp->m_sb.sb_rextsize;
-		/* Set prod to match the extent size */
-		prod = align / mp->m_sb.sb_rextsize;
-
-		error = xfs_bmap_extsize_align(mp, ap->gotp, ap->prevp,
-						align, rt, ap->eof, 0,
-						ap->conv, &ap->off, &ap->alen);
-		if (error)
-			return error;
-		ASSERT(ap->alen);
-		ASSERT(ap->alen % mp->m_sb.sb_rextsize == 0);
-
-		/*
-		 * If the offset & length are not perfectly aligned
-		 * then kill prod, it will just get us in trouble.
-		 */
-		if (do_mod(ap->off, align) || ap->alen % align)
-			prod = 1;
-		/*
-		 * Set ralen to be the actual requested length in rtextents.
-		 */
-		ralen = ap->alen / mp->m_sb.sb_rextsize;
-		/*
-		 * If the old value was close enough to MAXEXTLEN that
-		 * we rounded up to it, cut it back so it's valid again.
-		 * Note that if it's a really large request (bigger than
-		 * MAXEXTLEN), we don't hear about that number, and can't
-		 * adjust the starting point to match it.
-		 */
-		if (ralen * mp->m_sb.sb_rextsize >= MAXEXTLEN)
-			ralen = MAXEXTLEN / mp->m_sb.sb_rextsize;
-		/*
-		 * If it's an allocation to an empty file at offset 0,
-		 * pick an extent that will space things out in the rt area.
-		 */
-		if (ap->eof && ap->off == 0) {
-			error = xfs_rtpick_extent(mp, ap->tp, ralen, &rtx);
-			if (error)
-				return error;
-			ap->rval = rtx * mp->m_sb.sb_rextsize;
-		} else
-			ap->rval = 0;
-	} else {
-		align = (ap->userdata && ap->ip->i_d.di_extsize &&
-			(ap->ip->i_d.di_flags & XFS_DIFLAG_EXTSIZE)) ?
-			ap->ip->i_d.di_extsize : 0;
-		if (unlikely(align)) {
-			error = xfs_bmap_extsize_align(mp, ap->gotp, ap->prevp,
-							align, rt,
-							ap->eof, 0, ap->conv,
-							&ap->off, &ap->alen);
-			ASSERT(!error);
-			ASSERT(ap->alen);
-		}
-		if (nullfb)
-			ap->rval = XFS_INO_TO_FSB(mp, ap->ip->i_ino);
-		else
-			ap->rval = ap->firstblock;
-	}
-
 	/*
 	 * If allocating at eof, and there's a previous real block,
 	 * try to use it's last block as our starting point.
@@ -2514,25 +2439,73 @@ xfs_bmap_alloc(
 		else if (gotbno != NULLFSBLOCK)
 			ap->rval = gotbno;
 	}
+#undef ISVALID
+	return 0;
+}
+
+STATIC int
+xfs_bmap_rtalloc(
+	xfs_bmalloca_t	*ap)		/* bmap alloc argument struct */
+{
+	xfs_alloctype_t	atype = 0;	/* type for allocation routines */
+	int		error;		/* error return value */
+	xfs_mount_t	*mp;		/* mount point structure */
+	xfs_extlen_t	prod = 0;	/* product factor for allocators */
+	xfs_extlen_t	ralen = 0;	/* realtime allocation length */
+	xfs_extlen_t	align;		/* minimum allocation alignment */
+	xfs_rtblock_t	rtx;		/* realtime extent number */
+	xfs_rtblock_t	rtb;
+
+	mp = ap->ip->i_mount;
+	align = ap->ip->i_d.di_extsize ?
+		ap->ip->i_d.di_extsize : mp->m_sb.sb_rextsize;
+	prod = align / mp->m_sb.sb_rextsize;
+	error = xfs_bmap_extsize_align(mp, ap->gotp, ap->prevp,
+					align, 1, ap->eof, 0,
+					ap->conv, &ap->off, &ap->alen);
+	if (error)
+		return error;
+	ASSERT(ap->alen);
+	ASSERT(ap->alen % mp->m_sb.sb_rextsize == 0);
+
 	/*
-	 * If allowed, use ap->rval; otherwise must use firstblock since
-	 * it's in the right allocation group.
+	 * If the offset & length are not perfectly aligned
+	 * then kill prod, it will just get us in trouble.
 	 */
-	if (nullfb || rt || XFS_FSB_TO_AGNO(mp, ap->rval) == fb_agno)
-		;
-	else
-		ap->rval = ap->firstblock;
+	if (do_mod(ap->off, align) || ap->alen % align)
+		prod = 1;
 	/*
-	 * Realtime allocation, done through xfs_rtallocate_extent.
+	 * Set ralen to be the actual requested length in rtextents.
 	 */
-	if (rt) {
-#ifndef __KERNEL__
-		ASSERT(0);
-#else
-		xfs_rtblock_t	rtb;
+	ralen = ap->alen / mp->m_sb.sb_rextsize;
+	/*
+	 * If the old value was close enough to MAXEXTLEN that
+	 * we rounded up to it, cut it back so it's valid again.
+	 * Note that if it's a really large request (bigger than
+	 * MAXEXTLEN), we don't hear about that number, and can't
+	 * adjust the starting point to match it.
+	 */
+	if (ralen * mp->m_sb.sb_rextsize >= MAXEXTLEN)
+		ralen = MAXEXTLEN / mp->m_sb.sb_rextsize;
+	/*
+	 * If it's an allocation to an empty file at offset 0,
+	 * pick an extent that will space things out in the rt area.
+	 */
+	if (ap->eof && ap->off == 0) {
+		error = xfs_rtpick_extent(mp, ap->tp, ralen, &rtx);
+		if (error)
+			return error;
+		ap->rval = rtx * mp->m_sb.sb_rextsize;
+	} else {
+		ap->rval = 0;
+	}
 
-		atype = ap->rval == 0 ?
-			XFS_ALLOCTYPE_ANY_AG : XFS_ALLOCTYPE_NEAR_BNO;
+	xfs_bmap_adjacent(ap);
+
+	/*
+	 * Realtime allocation, done through xfs_rtallocate_extent.
+	 */
+	atype = ap->rval == 0 ?  XFS_ALLOCTYPE_ANY_AG : XFS_ALLOCTYPE_NEAR_BNO;
 	do_div(ap->rval, mp->m_sb.sb_rextsize);
 	rtb = ap->rval;
 	ap->alen = ralen;
@@ -2559,29 +2532,67 @@ xfs_bmap_alloc(
 		 */
 		XFS_TRANS_MOD_DQUOT_BYINO(mp, ap->tp, ap->ip,
 			ap->wasdel ? XFS_TRANS_DQ_DELRTBCOUNT :
-						XFS_TRANS_DQ_RTBCOUNT,
-				(long) ralen);
-		} else
+					XFS_TRANS_DQ_RTBCOUNT, (long) ralen);
+	} else {
 		ap->alen = 0;
-#endif	/* __KERNEL__ */
 	}
-	/*
-	 * Normal allocation, done through xfs_alloc_vextent.
-	 */
-	else {
+	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	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	delta;
-		int		isaligned;
 	xfs_extlen_t	longest;
 	xfs_extlen_t	need;
-		xfs_extlen_t	nextminlen=0;
-		int		notinit;
+	xfs_extlen_t	nextminlen = 0;
 	xfs_perag_t	*pag;
-		xfs_agnumber_t	startag;
+	int		nullfb;		/* true if ap->firstblock isn't set */
+	int		isaligned;
+	int		notinit;
 	int		tryagain;
+	int		error;
 
+	mp = ap->ip->i_mount;
+	align = (ap->userdata && ap->ip->i_d.di_extsize &&
+		(ap->ip->i_d.di_flags & XFS_DIFLAG_EXTSIZE)) ?
+		ap->ip->i_d.di_extsize : 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)
+		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;
@@ -2786,9 +2797,20 @@ xfs_bmap_alloc(
 		ap->rval = NULLFSBLOCK;
 		ap->alen = 0;
 	}
-	}
 	return 0;
-#undef	ISVALID
+}
+
+/*
+ * xfs_bmap_alloc is called by xfs_bmapi to allocate an extent for a file.
+ * It figures out where to ask the underlying allocator to put the new extent.
+ */
+STATIC int
+xfs_bmap_alloc(
+	xfs_bmalloca_t	*ap)		/* bmap alloc argument struct */
+{
+	if ((ap->ip->i_d.di_flags & XFS_DIFLAG_REALTIME) && ap->userdata)
+		return xfs_bmap_rtalloc(ap);
+	return xfs_bmap_btalloc(ap);
 }
 
 /*