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    SubjectRe: [PATCH] f2fs: fix long latency due to discard during umount
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    On 2020/3/18 12:44, Sahitya Tummala wrote:
    > F2FS already has a default timeout of 5 secs for discards that
    > can be issued during umount, but it can take more than the 5 sec
    > timeout if the underlying UFS device queue is already full and there
    > are no more available free tags to be used. In that case, submit_bio()
    > will wait for the already queued discard requests to complete to get
    > a free tag, which can potentially take way more than 5 sec.
    >
    > Fix this by submitting the discard requests with REQ_NOWAIT
    > flags during umount. This will return -EAGAIN for UFS queue/tag full
    > scenario without waiting in the context of submit_bio(). The FS can
    > then handle these requests by retrying again within the stipulated
    > discard timeout period to avoid long latencies.
    >
    > Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>

    Reviewed-by: Chao Yu <yuchao0@huawei.com>

    Thanks,

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