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From 430ff66f69074063dd824b0cde8808ee3d2c7ca8 Mon Sep 17 00:00:00 2001
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From: Raghavendra G <rgowdapp@redhat.com>
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Date: Fri, 22 Dec 2017 12:02:09 +0530
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Subject: [PATCH 156/180] performance/write-behind: fix bug while handling
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short writes
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The variabled "fulfilled" in wb_fulfill_short_write is not reset to 0
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while handling every member of the list.
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This has some interesting consequences:
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* If we break from the loop while processing last member of the list
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head->winds, req is reset to head as the list is a circular
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one. However, head is already fulfilled and can potentially be
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freed. So, we end up adding a freed request to wb_inode->todo
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list. This is the RCA for the crash tracked by the bug associated
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with this patch (Note that we saw "holder" which is freed in todo
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list).
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* If we break from the loop while processing any of the last but one
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member of the list head->winds, req is set to next member in the
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list, skipping the current request, even though it is not entirely
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synced. This can lead to data corruption.
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The fix is very simple and we've to change the code to make sure
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"fulfilled" reflects whether the current request is fulfilled or not
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and it doesn't carry history of previous requests in the list.
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Change-Id: Ia3d6988175a51c9e08efdb521a7b7938b01f93c8
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BUG: 1516638
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Signed-off-by: Raghavendra G <rgowdapp@redhat.com>
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upstream patch: https://review.gluster.org/19064
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Reviewed-on: https://code.engineering.redhat.com/gerrit/126512
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Tested-by: RHGS Build Bot <nigelb@redhat.com>
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Reviewed-by: Sunil Kumar Heggodu Gopala Acharya <sheggodu@redhat.com>
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---
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xlators/performance/write-behind/src/write-behind.c | 5 +++--
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1 file changed, 3 insertions(+), 2 deletions(-)
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diff --git a/xlators/performance/write-behind/src/write-behind.c b/xlators/performance/write-behind/src/write-behind.c
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index d1a95c9..7104eb9 100644
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--- a/xlators/performance/write-behind/src/write-behind.c
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+++ b/xlators/performance/write-behind/src/write-behind.c
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@@ -964,6 +964,7 @@ __wb_fulfill_short_write (wb_request_t *req, int size, gf_boolean_t *fulfilled)
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} else {
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accounted_size = size;
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__wb_modify_write_request (req, size);
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+ *fulfilled = 0;
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}
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out:
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@@ -1005,7 +1006,7 @@ wb_fulfill_short_write (wb_request_t *head, int size)
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size -= accounted_size;
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if (size == 0) {
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- if (fulfilled)
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+ if (fulfilled && (next != head))
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req = next;
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goto done;
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@@ -1017,7 +1018,7 @@ wb_fulfill_short_write (wb_request_t *head, int size)
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size -= accounted_size;
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if (size == 0) {
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- if (fulfilled)
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+ if (fulfilled && (next != head))
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req = next;
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break;
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}
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--
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1.8.3.1
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