xfs: use unhashed buffers for size checks

When we are checking we can access the last block of each device, we
do not need to use cached buffers as they will be tossed away
immediately. Use uncached buffers for size checks so that all IO
prior to full in-memory structure initialisation does not use the
buffer cache.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>

fs/xfs/xfs_fsops.c

@@ -144,12 +144,11 @@ xfs_growfs_data_private(
 	if ((error = xfs_sb_validate_fsb_count(&mp->m_sb, nb)))
 		return error;
 	dpct = pct - mp->m_sb.sb_imax_pct;
-	error = xfs_read_buf(mp, mp->m_ddev_targp,
-			XFS_FSB_TO_BB(mp, nb) - XFS_FSS_TO_BB(mp, 1),
-			XFS_FSS_TO_BB(mp, 1), 0, &bp);
-	if (error)
-		return error;
-	ASSERT(bp);
+	bp = xfs_buf_read_uncached(mp, mp->m_ddev_targp,
+				XFS_FSB_TO_BB(mp, nb) - XFS_FSS_TO_BB(mp, 1),
+				BBTOB(XFS_FSS_TO_BB(mp, 1)), 0);
+	if (!bp)
+		return EIO;
 	xfs_buf_relse(bp);
 
 	new = nb;	/* use new as a temporary here */

fs/xfs/xfs_mount.c

@@ -980,42 +980,35 @@ xfs_check_sizes(xfs_mount_t *mp)
 {
 	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");
+		cmn_err(CE_WARN, "XFS: filesystem size mismatch detected");
 		return XFS_ERROR(EFBIG);
 	}
-	error = xfs_read_buf(mp, mp->m_ddev_targp,
-			     d - XFS_FSS_TO_BB(mp, 1),
-			     XFS_FSS_TO_BB(mp, 1), 0, &bp);
-	if (!error) {
-		xfs_buf_relse(bp);
-	} else {
-		cmn_err(CE_WARN, "XFS: size check 2 failed");
-		if (error == ENOSPC)
-			error = XFS_ERROR(EFBIG);
-		return error;
+	bp = xfs_buf_read_uncached(mp, mp->m_ddev_targp,
+					d - XFS_FSS_TO_BB(mp, 1),
+					BBTOB(XFS_FSS_TO_BB(mp, 1)), 0);
+	if (!bp) {
+		cmn_err(CE_WARN, "XFS: last sector read failed");
+		return EIO;
 	}
+	xfs_buf_relse(bp);
 
 	if (mp->m_logdev_targp != mp->m_ddev_targp) {
 		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");
+			cmn_err(CE_WARN, "XFS: log size mismatch detected");
 			return XFS_ERROR(EFBIG);
 		}
-		error = xfs_read_buf(mp, mp->m_logdev_targp,
-				     d - XFS_FSB_TO_BB(mp, 1),
-				     XFS_FSB_TO_BB(mp, 1), 0, &bp);
-		if (!error) {
-			xfs_buf_relse(bp);
-		} else {
-			cmn_err(CE_WARN, "XFS: size check 3 failed");
-			if (error == ENOSPC)
-				error = XFS_ERROR(EFBIG);
-			return error;
+		bp = xfs_buf_read_uncached(mp, mp->m_logdev_targp,
+					d - XFS_FSB_TO_BB(mp, 1),
+					XFS_FSB_TO_B(mp, 1), 0);
+		if (!bp) {
+			cmn_err(CE_WARN, "XFS: log device read failed");
+			return EIO;
 		}
+		xfs_buf_relse(bp);
 	}
 	return 0;
 }

fs/xfs/xfs_rtalloc.c

@@ -39,6 +39,7 @@
 #include "xfs_trans_space.h"
 #include "xfs_utils.h"
 #include "xfs_trace.h"
+#include "xfs_buf.h"
 
 
 /*
@@ -1883,13 +1884,13 @@ xfs_growfs_rt(
 	/*
 	 * Read in the last block of the device, make sure it exists.
 	 */
-	error = xfs_read_buf(mp, mp->m_rtdev_targp,
-			XFS_FSB_TO_BB(mp, nrblocks - 1),
-			XFS_FSB_TO_BB(mp, 1), 0, &bp);
-	if (error)
-		return error;
-	ASSERT(bp);
+	bp = xfs_buf_read_uncached(mp, mp->m_rtdev_targp,
+				XFS_FSB_TO_BB(mp, nrblocks - 1),
+				XFS_FSB_TO_B(mp, 1), 0);
+	if (!bp)
+		return EIO;
 	xfs_buf_relse(bp);
+
 	/*
 	 * Calculate new parameters.  These are the final values to be reached.
 	 */
@@ -2215,7 +2216,6 @@ xfs_rtmount_init(
 {
 	xfs_buf_t	*bp;	/* buffer for last block of subvolume */
 	xfs_daddr_t	d;	/* address of last block of subvolume */
-	int		error;	/* error return value */
 	xfs_sb_t	*sbp;	/* filesystem superblock copy in mount */
 
 	sbp = &mp->m_sb;
@@ -2242,15 +2242,12 @@ xfs_rtmount_init(
 			(unsigned long long) mp->m_sb.sb_rblocks);
 		return XFS_ERROR(EFBIG);
 	}
-	error = xfs_read_buf(mp, mp->m_rtdev_targp,
-				d - XFS_FSB_TO_BB(mp, 1),
-				XFS_FSB_TO_BB(mp, 1), 0, &bp);
-	if (error) {
-		cmn_err(CE_WARN,
-	"XFS: realtime mount -- xfs_read_buf failed, returned %d", error);
-		if (error == ENOSPC)
-			return XFS_ERROR(EFBIG);
-		return error;
+	bp = xfs_buf_read_uncached(mp, mp->m_rtdev_targp,
+					d - XFS_FSB_TO_BB(mp, 1),
+					XFS_FSB_TO_B(mp, 1), 0);
+	if (!bp) {
+		cmn_err(CE_WARN, "XFS: realtime device size check failed");
+		return EIO;
 	}
 	xfs_buf_relse(bp);
 	return 0;