[PATCH] refactor xfs_mountfs for clarity & stack savings

[Eric Sandeen <sandeen@sandeen.net>]

(note, please feel free to re-check the error handling
in this change...)

------

Refactoring xfs_mountfs() to call sub-functions for logical
chunks can help save a bit of stack, and can make it easier to
read this long function.

The mount path is one of the longest common callchains, easily
getting to within a few bytes of the end of a 4k stack when
over lvm, quotas are enabled, and quotacheck must be done.

With this change on top of the other stack-related changes
I've sent, I can get xfs to survive a normal xfsqa run on
4k stacks over lvm.

Signed-off-by: Eric Sandeen <sandeen@sandeen.net

Index: linux-2.6-xfs/fs/xfs/xfs_mount.c
===================================================================
--- linux-2.6-xfs.orig/fs/xfs/xfs_mount.c
+++ linux-2.6-xfs/fs/xfs/xfs_mount.c
@@ -734,49 +734,13 @@ xfs_initialize_perag_data(xfs_mount_t *m
 }
 
 /*
- * xfs_mountfs
- *
- * This function does the following on an initial mount of a file system:
- *	- reads the superblock from disk and init the mount struct
- *	- if we're a 32-bit kernel, do a size check on the superblock
- *		so we don't mount terabyte filesystems
- *	- init mount struct realtime fields
- *	- allocate inode hash table for fs
- *	- init directory manager
- *	- perform recovery and init the log manager
+ * Update alignment values based on mount options and sb values
  */
-int
-xfs_mountfs(
-	xfs_mount_t	*mp,
-	int		mfsi_flags)
+STATIC int
+xfs_update_alignment(xfs_mount_t *mp, int mfsi_flags, __uint64_t *update_flags)
 {
-	xfs_buf_t	*bp;
 	xfs_sb_t	*sbp = &(mp->m_sb);
-	xfs_inode_t	*rip;
-	bhv_vnode_t	*rvp = NULL;
-	int		readio_log, writeio_log;
-	xfs_daddr_t	d;
-	__uint64_t	resblks;
-	__int64_t	update_flags;
-	uint		quotamount, quotaflags;
-	int		agno;
-	int		uuid_mounted = 0;
-	int		error = 0;
 
-	if (mp->m_sb_bp == NULL) {
-		if ((error = xfs_readsb(mp, mfsi_flags))) {
-			return error;
-		}
-	}
-	xfs_mount_common(mp, sbp);
-
-	/*
-	 * Check if sb_agblocks is aligned at stripe boundary
-	 * If sb_agblocks is NOT aligned turn off m_dalign since
-	 * allocator alignment is within an ag, therefore ag has
-	 * to be aligned at stripe boundary.
-	 */
-	update_flags = 0LL;
 	if (mp->m_dalign && !(mfsi_flags & XFS_MFSI_SECOND)) {
 		/*
 		 * If stripe unit and stripe width are not multiples
@@ -787,8 +751,7 @@ xfs_mountfs(
 			if (mp->m_flags & XFS_MOUNT_RETERR) {
 				cmn_err(CE_WARN,
 					"XFS: alignment check 1 failed");
-				error = XFS_ERROR(EINVAL);
-				goto error1;
+				return XFS_ERROR(EINVAL);
 			}
 			mp->m_dalign = mp->m_swidth = 0;
 		} else {
@@ -798,8 +761,7 @@ xfs_mountfs(
 			mp->m_dalign = XFS_BB_TO_FSBT(mp, mp->m_dalign);
 			if (mp->m_dalign && (sbp->sb_agblocks % mp->m_dalign)) {
 				if (mp->m_flags & XFS_MOUNT_RETERR) {
-					error = XFS_ERROR(EINVAL);
-					goto error1;
+					return XFS_ERROR(EINVAL);
 				}
 				xfs_fs_cmn_err(CE_WARN, mp,
 "stripe alignment turned off: sunit(%d)/swidth(%d) incompatible with agsize(%d)",
@@ -816,8 +778,7 @@ xfs_mountfs(
 "stripe alignment turned off: sunit(%d) less than bsize(%d)",
                                         	mp->m_dalign,
 						mp->m_blockmask +1);
-					error = XFS_ERROR(EINVAL);
-					goto error1;
+					return XFS_ERROR(EINVAL);
 				}
 				mp->m_swidth = 0;
 			}
@@ -830,11 +791,11 @@ xfs_mountfs(
 		if (XFS_SB_VERSION_HASDALIGN(sbp)) {
 			if (sbp->sb_unit != mp->m_dalign) {
 				sbp->sb_unit = mp->m_dalign;
-				update_flags |= XFS_SB_UNIT;
+				*update_flags |= XFS_SB_UNIT;
 			}
 			if (sbp->sb_width != mp->m_swidth) {
 				sbp->sb_width = mp->m_swidth;
-				update_flags |= XFS_SB_WIDTH;
+				*update_flags |= XFS_SB_WIDTH;
 			}
 		}
 	} else if ((mp->m_flags & XFS_MOUNT_NOALIGN) != XFS_MOUNT_NOALIGN &&
@@ -843,49 +804,45 @@ xfs_mountfs(
 			mp->m_swidth = sbp->sb_width;
 	}
 
-	xfs_alloc_compute_maxlevels(mp);
-	xfs_bmap_compute_maxlevels(mp, XFS_DATA_FORK);
-	xfs_bmap_compute_maxlevels(mp, XFS_ATTR_FORK);
-	xfs_ialloc_compute_maxlevels(mp);
+	return 0;
+}
 
-	if (sbp->sb_imax_pct) {
-		__uint64_t	icount;
+/*
+ * Set the maximum inode count for this filesystem
+ */
+STATIC void
+xfs_set_maxicount(xfs_mount_t *mp)
+{
+	xfs_sb_t	*sbp = &(mp->m_sb);
+	__uint64_t	icount;
 
-		/* Make sure the maximum inode count is a multiple of the
-		 * units we allocate inodes in.
+	if (sbp->sb_imax_pct) {
+		/*
+		 * Make sure the maximum inode count is a multiple
+		 * of the units we allocate inodes in.
 		 */
-
 		icount = sbp->sb_dblocks * sbp->sb_imax_pct;
 		do_div(icount, 100);
 		do_div(icount, mp->m_ialloc_blks);
 		mp->m_maxicount = (icount * mp->m_ialloc_blks)  <<
 				   sbp->sb_inopblog;
-	} else
+	} else {
 		mp->m_maxicount = 0;
-
-	mp->m_maxioffset = xfs_max_file_offset(sbp->sb_blocklog);
-
-	/*
-	 * XFS uses the uuid from the superblock as the unique
-	 * identifier for fsid.  We can not use the uuid from the volume
-	 * since a single partition filesystem is identical to a single
-	 * partition volume/filesystem.
-	 */
-	if ((mfsi_flags & XFS_MFSI_SECOND) == 0 &&
-	    (mp->m_flags & XFS_MOUNT_NOUUID) == 0) {
-		if (xfs_uuid_mount(mp)) {
-			error = XFS_ERROR(EINVAL);
-			goto error1;
-		}
-		uuid_mounted=1;
 	}
+}
+
+/*
+ * Set the default minimum read and write sizes unless
+ * already specified in a mount option.
+ * We use smaller I/O sizes when the file system
+ * is being used for NFS service (wsync mount option).
+ */
+STATIC void
+xfs_set_rw_sizes(xfs_mount_t *mp)
+{
+	xfs_sb_t	*sbp = &(mp->m_sb);
+	int		readio_log, writeio_log;
 
-	/*
-	 * Set the default minimum read and write sizes unless
-	 * already specified in a mount option.
-	 * We use smaller I/O sizes when the file system
-	 * is being used for NFS service (wsync mount option).
-	 */
 	if (!(mp->m_flags & XFS_MOUNT_DFLT_IOSIZE)) {
 		if (mp->m_flags & XFS_MOUNT_WSYNC) {
 			readio_log = XFS_WSYNC_READIO_LOG;
@@ -911,17 +868,14 @@ xfs_mountfs(
 		mp->m_writeio_log = writeio_log;
 	}
 	mp->m_writeio_blocks = 1 << (mp->m_writeio_log - sbp->sb_blocklog);
+}
 
-	/*
-	 * Set the inode cluster size.
-	 * This may still be overridden by the file system
-	 * block size if it is larger than the chosen cluster size.
-	 */
-	mp->m_inode_cluster_size = XFS_INODE_BIG_CLUSTER_SIZE;
-
-	/*
-	 * Set whether we're using inode alignment.
-	 */
+/*
+ * Set whether we're using inode alignment.
+ */
+STATIC void
+xfs_set_inoalignment(xfs_mount_t *mp)
+{
 	if (XFS_SB_VERSION_HASALIGN(&mp->m_sb) &&
 	    mp->m_sb.sb_inoalignmt >=
 	    XFS_B_TO_FSBT(mp, mp->m_inode_cluster_size))
@@ -937,14 +891,22 @@ xfs_mountfs(
 		mp->m_sinoalign = mp->m_dalign;
 	else
 		mp->m_sinoalign = 0;
-	/*
-	 * Check that the data (and log if separate) are an ok size.
-	 */
+}
+
+/*
+ * Check that the data (and log if separate) are an ok size.
+ */
+STATIC int
+xfs_check_sizes(xfs_mount_t *mp, int mfsi_flags)
+{
+	xfs_buf_t	*bp;
+	xfs_daddr_t	d;
+	int		error;
+
 	d = (xfs_daddr_t)XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks);
 	if (XFS_BB_TO_FSB(mp, d) != mp->m_sb.sb_dblocks) {
 		cmn_err(CE_WARN, "XFS: size check 1 failed");
-		error = XFS_ERROR(E2BIG);
-		goto error1;
+		return XFS_ERROR(E2BIG);
 	}
 	error = xfs_read_buf(mp, mp->m_ddev_targp,
 			     d - XFS_FSS_TO_BB(mp, 1),
@@ -956,7 +918,7 @@ xfs_mountfs(
 		if (error == ENOSPC) {
 			error = XFS_ERROR(E2BIG);
 		}
-		goto error1;
+		return error;
 	}
 
 	if (((mfsi_flags & XFS_MFSI_CLIENT) == 0) &&
@@ -964,8 +926,7 @@ xfs_mountfs(
 		d = (xfs_daddr_t)XFS_FSB_TO_BB(mp, mp->m_sb.sb_logblocks);
 		if (XFS_BB_TO_FSB(mp, d) != mp->m_sb.sb_logblocks) {
 			cmn_err(CE_WARN, "XFS: size check 3 failed");
-			error = XFS_ERROR(E2BIG);
-			goto error1;
+			return XFS_ERROR(E2BIG);
 		}
 		error = xfs_read_buf(mp, mp->m_logdev_targp,
 				     d - XFS_FSB_TO_BB(mp, 1),
@@ -977,11 +938,102 @@ xfs_mountfs(
 			if (error == ENOSPC) {
 				error = XFS_ERROR(E2BIG);
 			}
+			return error;
+		}
+	}
+	return 0;
+}
+
+/*
+ * xfs_mountfs
+ *
+ * This function does the following on an initial mount of a file system:
+ *	- reads the superblock from disk and init the mount struct
+ *	- if we're a 32-bit kernel, do a size check on the superblock
+ *		so we don't mount terabyte filesystems
+ *	- init mount struct realtime fields
+ *	- allocate inode hash table for fs
+ *	- init directory manager
+ *	- perform recovery and init the log manager
+ */
+int
+xfs_mountfs(
+	xfs_mount_t	*mp,
+	int		mfsi_flags)
+{
+	xfs_sb_t	*sbp = &(mp->m_sb);
+	xfs_inode_t	*rip;
+	bhv_vnode_t	*rvp = NULL;
+	__uint64_t	resblks;
+	__int64_t	update_flags = 0LL;
+	uint		quotamount, quotaflags;
+	int		agno;
+	int		uuid_mounted = 0;
+	int		error = 0;
+
+	if (mp->m_sb_bp == NULL) {
+		if ((error = xfs_readsb(mp, mfsi_flags))) {
+			return error;
+		}
+	}
+	xfs_mount_common(mp, sbp);
+
+	/*
+	 * Check if sb_agblocks is aligned at stripe boundary
+	 * If sb_agblocks is NOT aligned turn off m_dalign since
+	 * allocator alignment is within an ag, therefore ag has
+	 * to be aligned at stripe boundary.
+	 */
+	if ((error = xfs_update_alignment(mp, mfsi_flags, &update_flags)))
+		goto error1;
+
+	xfs_alloc_compute_maxlevels(mp);
+	xfs_bmap_compute_maxlevels(mp, XFS_DATA_FORK);
+	xfs_bmap_compute_maxlevels(mp, XFS_ATTR_FORK);
+	xfs_ialloc_compute_maxlevels(mp);
+
+	xfs_set_maxicount(mp);
+
+	mp->m_maxioffset = xfs_max_file_offset(sbp->sb_blocklog);
+
+	/*
+	 * XFS uses the uuid from the superblock as the unique
+	 * identifier for fsid.  We can not use the uuid from the volume
+	 * since a single partition filesystem is identical to a single
+	 * partition volume/filesystem.
+	 */
+	if ((mfsi_flags & XFS_MFSI_SECOND) == 0 &&
+	    (mp->m_flags & XFS_MOUNT_NOUUID) == 0) {
+		if (xfs_uuid_mount(mp)) {
+			error = XFS_ERROR(EINVAL);
 			goto error1;
 		}
 	}
 
 	/*
+	 * Set the minimum read and write sizes
+	 */
+	xfs_set_rw_sizes(mp);
+
+	/*
+	 * Set the inode cluster size.
+	 * This may still be overridden by the file system
+	 * block size if it is larger than the chosen cluster size.
+	 */
+	mp->m_inode_cluster_size = XFS_INODE_BIG_CLUSTER_SIZE;
+
+	/*
+	 * Set inode alignment fields
+	 */
+	xfs_set_inoalignment(mp);
+
+	/*
+	 * Check that the data (and log if separate) are an ok size.
+	 */
+	if ((error = xfs_check_sizes(mp, mfsi_flags)))
+		goto error1;
+
+	/*
 	 * Initialize realtime fields in the mount structure
 	 */
 	if ((error = xfs_rtmount_init(mp))) {