From efe78c6546e4f0d64a9b1f3877caee55c5821f2d Mon Sep 17 00:00:00 2001
From: Krzysztof Mazur <krzysiek@podlesie.net>
Date: Fri, 22 Jul 2011 21:48:42 +0200
Subject: [PATCH 47/84] lsbd: add lcache locking

This patch adds SMP locking of lcache.
---
 drivers/block/lsbd.c | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/block/lsbd.c b/drivers/block/lsbd.c
index a817a1d..6e3176f 100644
--- a/drivers/block/lsbd.c
+++ b/drivers/block/lsbd.c
@@ -101,6 +101,7 @@ struct lsbd {
 	unsigned long sectors_written;
 	unsigned long blocks_written;
 
+	rwlock_t lcache_lock;
 	lsbd_lcache_t *lcache;
 	unsigned int cur_lcache;
 
@@ -1211,8 +1212,10 @@ static int lsbd_partition(struct lsbd *p, struct lsbd_part_info *part)
 			for (i = 0; i < p->lsectors; i++)
 				l[i] = p->lcache[i];
 
+			write_lock(&p->lcache_lock);
 			ol = p->lcache;
 			p->lcache = l;
+			write_unlock(&p->lcache_lock);
 
 			lsbd_start(p);
 
@@ -1440,6 +1443,8 @@ static int lsbd_read_mirrored(struct lsbd *p, struct buffer_head *bh,
  * @p: LSBD device
  * @lsector: logical sector
  * @sector: current logical sector mapping
+ *
+ * This function should be called with locked lcache_lock for write.
  */
 static int lsbd_switch_mirror(struct lsbd *p, unsigned int lsector,
 		unsigned int sector)
@@ -1489,7 +1494,9 @@ static int lsbd_make_read(struct lsbd *p, int rw, struct buffer_head *bh)
 		return 0;
 	}
 
+	read_lock(&p->lcache_lock);
 	sector = p->lcache[lsector];
+	read_unlock(&p->lcache_lock);
 	lsbd_debug(p, "read %d, mapped to %d\n", lsector, sector);
 	if (sector == LSBD_SECT_INVALID) {
 		buffer_IO_error(bh);
@@ -1511,7 +1518,7 @@ static int lsbd_make_read(struct lsbd *p, int rw, struct buffer_head *bh)
 	 * just remapped to lower level device
 	 */
 	if (!p->mirrored) {
-		bh->b_rsector = (unsigned long) p->lcache[lsector] << 3;
+		bh->b_rsector = (unsigned long) sector << 3;
 		lsbd_debug(p, "mapped to physical %ld\n", bh->b_rsector);
 
 		bh->b_rdev = p->dev;
@@ -1527,9 +1534,13 @@ static int lsbd_make_read(struct lsbd *p, int rw, struct buffer_head *bh)
 		return 0;
 
 	p->read_errors++;
+
 	/* try to switch this sector to mirror and retry */
+	write_lock(&p->lcache_lock);
 	lsbd_switch_mirror(p, lsector, sector);
 	sector = p->lcache[lsector];
+	write_unlock(&p->lcache_lock);
+
 	if (sector >= p->psectors) {
 		lsbd_info(p, "invalid lcache entry: %d -> %d\n",
 				lsector, sector);
@@ -1677,15 +1688,18 @@ void lsbd_clean_block(struct lsbd *p)
 	for (i = 0; i < sectors; i++) {
 		unsigned int sector_id = be32_to_cpu(sects[i].id);
 		unsigned int s = block * p->sectors_per_block + i + 1;
+		unsigned int sector;
 
 		if (sector_id >= p->lsectors)
 			continue;
 
+		read_lock(&p->lcache_lock);
+		sector = p->lcache[sector_id];
+		read_unlock(&p->lcache_lock);
 		lsbd_debug(p, "block %ld.%ld: logical %d, phys %d, "
 				"lcache %d\n",
-				block, i, sector_id, s,
-				(unsigned int) p->lcache[sector_id]);
-		if (p->lcache[sector_id] == s) {
+				block, i, sector_id, s, sector);
+		if (sector == s) {
 			rbh = lsbd_sread(p, block, i + 1);
 			if (rbh == NULL)
 				continue;
@@ -1773,6 +1787,7 @@ static int lsbd_write_lcache(struct lsbd *p, void *bp)
 	b->lcache_chunk = cpu_to_be32(chunk);
 	cache = (void *) ((char *) bp + be32_to_cpu(b->lcache_offset));
 
+	read_lock(&p->lcache_lock);
 	for (i = 0; i < chunk; i++) {
 		unsigned long long sector_id = p->cur_lcache + i;
 
@@ -1780,6 +1795,7 @@ static int lsbd_write_lcache(struct lsbd *p, void *bp)
 			break;
 		cache[i] = cpu_to_be32(p->lcache[sector_id]);
 	}
+	read_unlock(&p->lcache_lock);
 	b->lcache_checksum = cpu_to_be32(lsbd_checksum(cache,
 				chunk * sizeof(*cache)));
 
@@ -1929,9 +1945,13 @@ static int lsbd_write_block(struct lsbd *p)
 
 			BUG_ON(r->sector >= p->lsectors);
 			sects[i].id = cpu_to_be32(r->sector);
+
+			write_lock(&p->lcache_lock);
 			p->lcache[r->sector] = p->cur_block
 				* p->sectors_per_block + i + 1;
 			BUG_ON(p->lcache[r->sector] >= p->psectors);
+			write_unlock(&p->lcache_lock);
+
 			memcpy(bh[i + 1]->b_data, r->bh->b_data,
 					p->sector_size);
 			move = r->move;
-- 
1.8.4.652.g0d6e0ce