Re: [PATCH] smb: client: set replay flag on the read send-error retry path

[Namjae Jeon]

On Thu, Jul 30, 2026 at 4:24 AM Christopher Lusk <clusk@xxxxxxxxxxxxx> wrote:
>
> smb2_async_readv() and smb2_async_writev() end with the same
> send-error block: if the error is replayable and smb2_should_replay()
> agrees, tell netfs to retry the subrequest. The write path also sets
> wdata->replay. The read path does not set rdata->replay.
>
> smb2_should_replay() is not a pure predicate. It consumes the retry
> budget and computes the exponential back-off, doubling cur_sleep up to
> CIFS_MAX_SLEEP. That back-off is only applied where the replay flag is
> tested at the top of the reissued request:
>
>         if (rdata->replay) {
>                 /* Back-off before retry */
>                 if (rdata->cur_sleep)
>                         msleep(rdata->cur_sleep);
>                 smb2_set_replay(server, &rqst);
>         }
>
> So on the read path the back-off is recomputed on every send-error
> retry and then discarded, and SMB2_FLAGS_REPLAY_OPERATION is not set
> on the reissued request.
>
> netfs does not pace the retry either. netfs_reissue_read() calls
> ->issue_read() directly, and fs/netfs/read_retry.c contains no delay
> of its own, so read send-error retries reissue immediately while the
> equivalent write retries back off.
>
> The read response callback already sets rdata->replay under the same
> conditions, so the read path does use the replay mechanism. Only this
> send-error path omits it.
>
> Where the back-off belongs was settled while the commit below was
> under review. David Howells asked whether netfslib should be doing the
> back-off [1], and objected to sleeping inside the response callback
> because that runs in the cifsd thread and would stall the socket [2].
> The sleep was therefore taken out of smb2_should_replay() and moved to
> just before the replay in smb2_async_readv() and smb2_async_writev()
> [3]. Setting the flag here preserves that arrangement: the sleep still
> happens at the top of the reissued request, not in a callback.
>
> Set rdata->replay here, matching smb2_async_writev().
>
> Fixes: 2c1238a7477a ("cifs: make retry logic in read/write path consistent with other paths")
> Link: https://lore.kernel.org/all/1652858.1769038134@xxxxxxxxxxxxxxxxxxxxxx/ [1]
> Link: https://lore.kernel.org/all/1653031.1769038583@xxxxxxxxxxxxxxxxxxxxxx/ [2]
> Link: https://lore.kernel.org/all/CANT5p=pXP3+CywpmK-on2uTvxO3S=31_B85_UDR7RoK1dQVtMA@xxxxxxxxxxxxxx/ [3]
> Assisted-by: Codex:gpt-5.5
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: Christopher Lusk <clusk@xxxxxxxxxxxxx>
I will apply it to #for-next.
Thanks!