Teach the (gpt)zfsboot and zfsloader raidz code to use its buffers

more efficiently.

Before this patch, in the worst case memory use would increase
exponentially on the number of drives in the raidz vdev.

Submitted by:	Matt Reimer <mattjreimer@gmail.com>
Sponsored by:	VPOP Technologies, Inc.
Silence from:	dfr

1 files changed, 29 insertions, 21 deletions

diff --git a/sys/cddl/boot/zfs/zfssubr.c b/sys/cddl/boot/zfs/zfssubr.c
index 4013986..25d349b 100644
--- a/sys/cddl/boot/zfs/zfssubr.c
+++ b/sys/cddl/boot/zfs/zfssubr.c
@@ -454,7 +454,7 @@ vdev_raidz_reconstruct_q(raidz_col_t *cols, int nparity, int acols, int x)
 
 static void
 vdev_raidz_reconstruct_pq(raidz_col_t *cols, int nparity, int acols,
-    int x, int y)
+    int x, int y, void *temp_p, void *temp_q)
 {
 	uint8_t *p, *q, *pxy, *qxy, *xd, *yd, tmp, a, b, aexp, bexp;
 	void *pdata, *qdata;
@@ -478,10 +478,8 @@ vdev_raidz_reconstruct_pq(raidz_col_t *cols, int nparity, int acols,
 	xsize = cols[x].rc_size;
 	ysize = cols[y].rc_size;
 
-	cols[VDEV_RAIDZ_P].rc_data =
-		zfs_alloc_temp(cols[VDEV_RAIDZ_P].rc_size);
-	cols[VDEV_RAIDZ_Q].rc_data =
-		zfs_alloc_temp(cols[VDEV_RAIDZ_Q].rc_size);
+	cols[VDEV_RAIDZ_P].rc_data = temp_p;
+	cols[VDEV_RAIDZ_Q].rc_data = temp_q;
 	cols[x].rc_size = 0;
 	cols[y].rc_size = 0;
 
@@ -551,9 +549,12 @@ vdev_raidz_read(vdev_t *vdev, const blkptr_t *bp, void *buf,
 	uint64_t f = b % dcols;
 	uint64_t o = (b / dcols) << unit_shift;
 	uint64_t q, r, coff;
-	int c, c1, bc, col, acols, devidx, asize, n;
+	int c, c1, bc, col, acols, devidx, asize, n, max_rc_size;
 	static raidz_col_t cols[16];
 	raidz_col_t *rc, *rc1;
+	void *orig, *orig1, *temp_p, *temp_q;
+
+	orig = orig1 = temp_p = temp_q = NULL;
 
 	q = s / (dcols - nparity);
 	r = s - q * (dcols - nparity);
@@ -561,6 +562,7 @@ vdev_raidz_read(vdev_t *vdev, const blkptr_t *bp, void *buf,
 
 	acols = (q == 0 ? bc : dcols);
 	asize = 0;
+	max_rc_size = 0;
 	
 	for (c = 0; c < acols; c++) {
 		col = f + c;
@@ -577,6 +579,8 @@ vdev_raidz_read(vdev_t *vdev, const blkptr_t *bp, void *buf,
 		cols[c].rc_tried = 0;
 		cols[c].rc_skipped = 0;
 		asize += cols[c].rc_size;
+		if (cols[c].rc_size > max_rc_size)
+			max_rc_size = cols[c].rc_size;
 	}
 
 	asize = roundup(asize, (nparity + 1) << unit_shift);
@@ -777,8 +781,13 @@ reconstruct:
 			//ASSERT(c != acols);
 			//ASSERT(!rc->rc_skipped || rc->rc_error == ENXIO || rc->rc_error == ESTALE);
 
+			if (temp_p == NULL)
+				temp_p = zfs_alloc_temp(max_rc_size);
+			if (temp_q == NULL)
+				temp_q = zfs_alloc_temp(max_rc_size);
+
 			vdev_raidz_reconstruct_pq(cols, nparity, acols,
-			    c1, c);
+			    c1, c, temp_p, temp_q);
 
 			if (zio_checksum_error(bp, buf) == 0)
 				return (0);
@@ -845,18 +854,12 @@ reconstruct:
 		return (EIO);
 	}
 
-	asize = 0;
-	for (c = 0; c < acols; c++) {
-		rc = &cols[c];
-		if (rc->rc_size > asize)
-			asize = rc->rc_size;
-	}
 	if (cols[VDEV_RAIDZ_P].rc_error == 0) {
 		/*
 		 * Attempt to reconstruct the data from parity P.
 		 */
-		void *orig;
-		orig = zfs_alloc_temp(asize);
+		if (orig == NULL)
+			orig = zfs_alloc_temp(max_rc_size);
 		for (c = nparity; c < acols; c++) {
 			rc = &cols[c];
 
@@ -874,8 +877,8 @@ reconstruct:
 		/*
 		 * Attempt to reconstruct the data from parity Q.
 		 */
-		void *orig;
-		orig = zfs_alloc_temp(asize);
+		if (orig == NULL)
+			orig = zfs_alloc_temp(max_rc_size);
 		for (c = nparity; c < acols; c++) {
 			rc = &cols[c];
 
@@ -895,9 +898,14 @@ reconstruct:
 		/*
 		 * Attempt to reconstruct the data from both P and Q.
 		 */
-		void *orig, *orig1;
-		orig = zfs_alloc_temp(asize);
-		orig1 = zfs_alloc_temp(asize);
+		if (orig == NULL)
+			orig = zfs_alloc_temp(max_rc_size);
+		if (orig1 == NULL)
+			orig1 = zfs_alloc_temp(max_rc_size);
+		if (temp_p == NULL)
+			temp_p = zfs_alloc_temp(max_rc_size);
+		if (temp_q == NULL)
+			temp_q = zfs_alloc_temp(max_rc_size);
 		for (c = nparity; c < acols - 1; c++) {
 			rc = &cols[c];
 
@@ -909,7 +917,7 @@ reconstruct:
 				memcpy(orig1, rc1->rc_data, rc1->rc_size);
 
 				vdev_raidz_reconstruct_pq(cols, nparity,
-				    acols, c, c1);
+				    acols, c, c1, temp_p, temp_q);
 
 				if (zio_checksum_error(bp, buf) == 0)
 					return (0);