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authorChristoph Hellwig <hch@lst.de>2015-05-22 09:14:04 -0400
committerJens Axboe <axboe@fb.com>2015-05-22 08:58:57 -0600
commit5f1b670d0bef508a5554d92525f5f6d00d640b38 (patch)
tree18aaa4b5ead87568214b3d9c0f501d8a98c2a787 /include/linux/blk_types.h
parent326e1dbb57368087a36607aaebe9795b8d5453e5 (diff)
block, dm: don't copy bios for request clones
Currently dm-multipath has to clone the bios for every request sent to the lower devices, which wastes cpu cycles and ties down memory. This patch instead adds a new REQ_CLONE flag that instructs req_bio_endio to not complete bios attached to a request, which we set on clone requests similar to bios in a flush sequence. With this change I/O errors on a path failure only get propagated to dm-multipath, which can then either resubmit the I/O or complete the bios on the original request. I've done some basic testing of this on a Linux target with ALUA support, and it survives path failures during I/O nicely. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'include/linux/blk_types.h')
-rw-r--r--include/linux/blk_types.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 3f4ded0b1a34..45a6be89957c 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -192,6 +192,7 @@ enum rq_flag_bits {
__REQ_HASHED, /* on IO scheduler merge hash */
__REQ_MQ_INFLIGHT, /* track inflight for MQ */
__REQ_NO_TIMEOUT, /* requests may never expire */
+ __REQ_CLONE, /* cloned bios */
__REQ_NR_BITS, /* stops here */
};
@@ -246,5 +247,6 @@ enum rq_flag_bits {
#define REQ_HASHED (1ULL << __REQ_HASHED)
#define REQ_MQ_INFLIGHT (1ULL << __REQ_MQ_INFLIGHT)
#define REQ_NO_TIMEOUT (1ULL << __REQ_NO_TIMEOUT)
+#define REQ_CLONE (1ULL << __REQ_CLONE)
#endif /* __LINUX_BLK_TYPES_H */