linux-kernel - [PATCH 11/18] scsi xcopy: keep cache of failures

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.LRH.2.02.1410220929260.31351@file01.intranet.prod.int.rdu2.redhat.com>
Date:	Wed, 22 Oct 2014 09:29:54 -0400 (EDT)
From:	Mikulas Patocka <mpatocka@...hat.com>
To:	"Alasdair G. Kergon" <agk@...hat.com>,
	Mike Snitzer <msnitzer@...hat.com>,
	Jonathan Brassow <jbrassow@...hat.com>,
	Edward Thornber <thornber@...hat.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@...radead.org>
cc:	dm-devel@...hat.com, linux-kernel@...r.kernel.org,
	linux-scsi@...r.kernel.org
Subject: [PATCH 11/18] scsi xcopy: keep cache of failures

If xcopy between two devices fails, it is pointless to send more xcopy
command between there two devices because they take time and they will
likely also fail.

This patch keeps a cache of (source_device,destination_device) pairs where
copying failed and makes sure that no xcopy command is sooner than 30
seconds after the last failure.

Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>

---
 drivers/scsi/sd.c |   35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

Index: linux-3.18-rc1/drivers/scsi/sd.c
===================================================================
--- linux-3.18-rc1.orig/drivers/scsi/sd.c	2014-10-21 00:49:21.000000000 +0200
+++ linux-3.18-rc1/drivers/scsi/sd.c	2014-10-21 00:49:24.000000000 +0200
@@ -943,6 +943,26 @@ static void sd_config_copy(struct scsi_d
 				   (logical_block_size >> 9));
 }
 
+#define SD_COPY_DISABLED_CACHE_TIME		(HZ * 30)
+#define SD_COPY_DISABLED_CACHE_HASH_BITS	6
+#define SD_COPY_DISABLED_CACHE_HASH		(1 << SD_COPY_DISABLED_CACHE_HASH_BITS)
+
+struct sd_copy_disabled_cache_entry {
+	struct scsi_device *src;
+	struct scsi_device *dst;
+	unsigned long jiffies;
+};
+
+static struct sd_copy_disabled_cache_entry sd_copy_disabled_cache[SD_COPY_DISABLED_CACHE_HASH];
+
+static struct sd_copy_disabled_cache_entry *sd_copy_disabled_cache_hash(
+	struct scsi_device *src, struct scsi_device *dst)
+{
+	return &sd_copy_disabled_cache[
+		hash_long((unsigned long)src + ((unsigned long)dst >> 1), SD_COPY_DISABLED_CACHE_HASH_BITS)
+	];
+}
+
 static int sd_setup_copy_cmnd(struct scsi_cmnd *cmd)
 {
 	struct request *rq = cmd->request;
@@ -955,6 +975,7 @@ static int sd_setup_copy_cmnd(struct scs
 	struct bio *bio = rq->bio;
 	struct page *page;
 	unsigned char *buf;
+	struct sd_copy_disabled_cache_entry *e;
 
 	dst_sdp = scsi_disk(rq->rq_disk)->device;
 	dst_queue = rq->rq_disk->queue;
@@ -974,6 +995,12 @@ static int sd_setup_copy_cmnd(struct scs
 	if (src_sdp->sector_size != dst_sdp->sector_size)
 		return BLKPREP_KILL;
 
+	/* The copy failed in the past, so do not retry it for some time */
+	e = sd_copy_disabled_cache_hash(src_sdp, dst_sdp);
+	if (unlikely(jiffies - ACCESS_ONCE(e->jiffies) < SD_COPY_DISABLED_CACHE_TIME) &&
+	    likely(ACCESS_ONCE(e->src) == src_sdp) && likely(ACCESS_ONCE(e->dst) == dst_sdp))
+		return BLKPREP_KILL;
+
 	dst_lba = blk_rq_pos(rq) >> (ilog2(dst_sdp->sector_size) - 9);
 	src_lba = bio->bi_copy->pair[0]->bi_iter.bi_sector >> (ilog2(src_sdp->sector_size) - 9);
 	nr_blocks = blk_rq_sectors(rq) >> (ilog2(dst_sdp->sector_size) - 9);
@@ -1937,11 +1964,19 @@ static int sd_done(struct scsi_cmnd *SCp
 			}
 		} else if (sshdr.asc == 0x26) {
 			switch (op) {
+				struct sd_copy_disabled_cache_entry *e;
+				struct scsi_device *src_sdp, *dst_sdp;
 			/*
 			 * Copying between two arrays that support XCOPY, but
 			 * cannot access each other.
 			 */
 			case EXTENDED_COPY:
+				dst_sdp = sdkp->device;
+				src_sdp = scsi_disk(req->bio->bi_copy->pair[0]->bi_bdev->bd_disk)->device;
+				e = sd_copy_disabled_cache_hash(src_sdp, dst_sdp);
+				ACCESS_ONCE(e->src) = src_sdp;
+				ACCESS_ONCE(e->dst) = dst_sdp;
+				ACCESS_ONCE(e->jiffies) = jiffies;
 				good_bytes = 0;
 				req->__data_len = blk_rq_bytes(req);
 				req->cmd_flags |= REQ_QUIET;

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/