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userfaultfd: reset err to be 0 when move_pages_ptes succeeded

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During move_pages() operation, when move_pages_ptes() returns EAGAIN, the
error code is not cleared even after we processed it.  This leads to a
successful retry but then the same pages are retried again due to the
stale error code.  This time move fails because pages are already moved,
loop is terminated and move_pages() reports a failure.  Clear the error
code once we processes EAGAIN.

Link: https://lore.kernel.org/e1e0b5f8-c3c6-0537-670b-4397f822f980@gmail.com
Fixes: 5094469205 ("userfaultfd: opportunistic TLB-flush batching for present pages in MOVE")
Assisted-by: ChatGPT:GPT-5.6-Luna
Signed-off-by: Bryan Lim <foxieflakey@gmail.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Bryan Lim 2026-08-19 10:08:24 +07:00 committed by Andrew Morton
parent 2fd4e76936
commit f025ca73de
1 changed files with 3 additions and 1 deletions
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4
mm/userfaultfd.c
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@ -2171,8 +2171,10 @@ static ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start,
}
if (err) {
if (err == -EAGAIN)
if (err == -EAGAIN) {
err = 0;
continue;
}
break;
}