parent
1966fd8d99
commit
771f295a0f
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@ -34,6 +34,9 @@ linux (4.19.7-1~exp1) UNRELEASED; urgency=medium
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* debian/rules: Mark more targets as phony
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* libcpupower: Hide private function and drop it from .symbols file
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[ Salvatore Bonaccorso ]
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* blk-mq: fix corruption with direct issue (Closes: #915666)
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-- Uwe Kleine-König <ukleinek@debian.org> Wed, 28 Nov 2018 12:20:46 +0100
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linux (4.19.5-1~exp1) experimental; urgency=medium
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@ -0,0 +1,99 @@
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From: Jens Axboe <axboe@kernel.dk>
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Date: Tue, 4 Dec 2018 20:06:48 -0700
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Subject: blk-mq: fix corruption with direct issue
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Origin: https://git.kernel.org/linus/ffe81d45322cc3cb140f0db080a4727ea284661e
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Bug-Debian: https://bugs.debian.org/915666
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If we attempt a direct issue to a SCSI device, and it returns BUSY, then
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we queue the request up normally. However, the SCSI layer may have
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already setup SG tables etc for this particular command. If we later
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merge with this request, then the old tables are no longer valid. Once
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we issue the IO, we only read/write the original part of the request,
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not the new state of it.
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This causes data corruption, and is most often noticed with the file
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system complaining about the just read data being invalid:
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[ 235.934465] EXT4-fs error (device sda1): ext4_iget:4831: inode #7142: comm dpkg-query: bad extra_isize 24937 (inode size 256)
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because most of it is garbage...
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This doesn't happen from the normal issue path, as we will simply defer
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the request to the hardware queue dispatch list if we fail. Once it's on
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the dispatch list, we never merge with it.
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Fix this from the direct issue path by flagging the request as
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REQ_NOMERGE so we don't change the size of it before issue.
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See also:
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https://bugzilla.kernel.org/show_bug.cgi?id=201685
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Tested-by: Guenter Roeck <linux@roeck-us.net>
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Fixes: 6ce3dd6eec1 ("blk-mq: issue directly if hw queue isn't busy in case of 'none'")
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Cc: stable@vger.kernel.org
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Signed-off-by: Jens Axboe <axboe@kernel.dk>
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---
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block/blk-mq.c | 26 +++++++++++++++++++++++++-
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1 file changed, 25 insertions(+), 1 deletion(-)
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diff --git a/block/blk-mq.c b/block/blk-mq.c
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index 3f91c6e5b17a..3262d83b9e07 100644
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--- a/block/blk-mq.c
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+++ b/block/blk-mq.c
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@@ -1715,6 +1715,15 @@ static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
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break;
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case BLK_STS_RESOURCE:
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case BLK_STS_DEV_RESOURCE:
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+ /*
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+ * If direct dispatch fails, we cannot allow any merging on
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+ * this IO. Drivers (like SCSI) may have set up permanent state
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+ * for this request, like SG tables and mappings, and if we
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+ * merge to it later on then we'll still only do IO to the
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+ * original part.
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+ */
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+ rq->cmd_flags |= REQ_NOMERGE;
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+
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blk_mq_update_dispatch_busy(hctx, true);
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__blk_mq_requeue_request(rq);
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break;
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@@ -1727,6 +1736,18 @@ static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
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return ret;
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}
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+/*
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+ * Don't allow direct dispatch of anything but regular reads/writes,
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+ * as some of the other commands can potentially share request space
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+ * with data we need for the IO scheduler. If we attempt a direct dispatch
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+ * on those and fail, we can't safely add it to the scheduler afterwards
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+ * without potentially overwriting data that the driver has already written.
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+ */
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+static bool blk_rq_can_direct_dispatch(struct request *rq)
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+{
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+ return req_op(rq) == REQ_OP_READ || req_op(rq) == REQ_OP_WRITE;
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+}
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+
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static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
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struct request *rq,
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blk_qc_t *cookie,
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@@ -1748,7 +1769,7 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
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goto insert;
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}
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- if (q->elevator && !bypass_insert)
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+ if (!blk_rq_can_direct_dispatch(rq) || (q->elevator && !bypass_insert))
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goto insert;
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if (!blk_mq_get_dispatch_budget(hctx))
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@@ -1810,6 +1831,9 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
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struct request *rq = list_first_entry(list, struct request,
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queuelist);
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+ if (!blk_rq_can_direct_dispatch(rq))
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+ break;
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+
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list_del_init(&rq->queuelist);
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ret = blk_mq_request_issue_directly(rq);
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if (ret != BLK_STS_OK) {
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--
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2.20.0.rc2
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@ -91,6 +91,7 @@ bugfix/all/fs-add-module_softdep-declarations-for-hard-coded-cr.patch
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bugfix/all/partially-revert-usb-kconfig-using-select-for-usb_co.patch
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bugfix/all/kbuild-include-addtree-remove-quotes-before-matching-path.patch
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debian/revert-objtool-fix-config_stack_validation-y-warning.patch
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bugfix/all/blk-mq-fix-corruption-with-direct-issue.patch
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# Miscellaneous features
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Loading…
Reference in New Issue