Messages in this thread Patch in this message | | | From | Pavel Shilovsky <> | Date | Tue, 5 Mar 2019 11:47:32 -0800 | Subject | Re: [PATCH 1/2] CIFS: Fix a bug with re-sending wdata when transport returning -EAGAIN |
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пт, 1 мар. 2019 г. в 19:04, Long Li <longli@linuxonhyperv.com>: > > From: Long Li <longli@microsoft.com> > > When sending a wdata, transport may return -EAGAIN. In this case > we should re-obtain credits because the session may have been > reconnected. > > Signed-off-by: Long Li <longli@microsoft.com> > --- > fs/cifs/file.c | 61 +++++++++++++++++++++++++------------------------- > 1 file changed, 31 insertions(+), 30 deletions(-) > > diff --git a/fs/cifs/file.c b/fs/cifs/file.c > index 9b53f33137b3..08e73759d6ec 100644 > --- a/fs/cifs/file.c > +++ b/fs/cifs/file.c > @@ -2620,43 +2620,44 @@ cifs_resend_wdata(struct cifs_writedata *wdata, struct list_head *wdata_list, > struct TCP_Server_Info *server = > tlink_tcon(wdata->cfile->tlink)->ses->server; > > - /* > - * Wait for credits to resend this wdata. > - * Note: we are attempting to resend the whole wdata not in segments > - */ > do { > - rc = server->ops->wait_mtu_credits(server, wdata->bytes, &wsize, > - &credits); > - > - if (rc) > - goto out; > - > - if (wsize < wdata->bytes) { > - add_credits_and_wake_if(server, &credits, 0); > - msleep(1000); > - } > - } while (wsize < wdata->bytes); > + /* > + * Wait for credits to resend this wdata. > + * Note: we are attempting to resend the whole wdata not in > + * segments > + */ > + do { > + rc = server->ops->wait_mtu_credits(server, wdata->bytes, > + &wsize, &credits);
The steps in write/read codepaths have been recently re-ordered: now we need to first check the open handle, re-open it if needed and then attempt to get credits. This approach avoid a possibility to be stuck waiting for credits because generally cifs_reopen_file() may need a lot of credits to complete (up to 2 SMB2_CREATE commands and arbitrary number of SMB2_LOCK commands).
Please look at this loop as an example: https://git.samba.org/?p=sfrench/cifs-2.6.git;a=blob;f=fs/cifs/file.c;h=bf864123093162c7ef5cd49ee08d8b40ad7938c8;hb=778d81b65e4d596251943002522d94a7c6fbcf69#l2690
> + if (rc) > + goto fail; > + > + if (wsize < wdata->bytes) { > + add_credits_and_wake_if(server, &credits, 0); > + msleep(1000); > + } > + } while (wsize < wdata->bytes); > > - wdata->credits = credits; > - rc = -EAGAIN; > - while (rc == -EAGAIN) { > + wdata->credits = credits;
let's call adjust_credits before calling async_writev() as in the example above.
> rc = 0; > if (wdata->cfile->invalidHandle) > rc = cifs_reopen_file(wdata->cfile, false); > if (!rc) > rc = server->ops->async_writev(wdata, > - cifs_uncached_writedata_release); > - } > + cifs_uncached_writedata_release); > > - if (!rc) { > - list_add_tail(&wdata->list, wdata_list); > - return 0; > - } > + /* If the write was successfully sent, we are done */ > + if (!rc) { > + list_add_tail(&wdata->list, wdata_list); > + return 0; > + } > > - add_credits_and_wake_if(server, &wdata->credits, 0); > -out: > - kref_put(&wdata->refcount, cifs_uncached_writedata_release); > + /* Roll back credits and retry if needed */ > + add_credits_and_wake_if(server, &wdata->credits, 0); > + } while (rc == -EAGAIN);
I don't think there is a need for the nested loop here. How about just do:
do { if (wdata->cfile->invalidHandle) { rc = cifs_reopen_file(...); if (rc) break; }
// get_credits // if not enough credits - wait and continue the loop.
rc = adjust_credits(...); if (!rc) { if (wdata->cfile->invalidHandle) // set rc, put credits and continue the loop. else // send async write } // handle write errors } while(rc == -EAGAIN);
> > +fail: > + kref_put(&wdata->refcount, cifs_uncached_writedata_release); > return rc; > } > > @@ -2884,12 +2885,12 @@ static void collect_uncached_write_data(struct cifs_aio_ctx *ctx) > wdata->bytes, &tmp_from, > ctx->cfile, cifs_sb, &tmp_list, > ctx); > + > + kref_put(&wdata->refcount, > + cifs_uncached_writedata_release); > } > > list_splice(&tmp_list, &ctx->list); > - > - kref_put(&wdata->refcount, > - cifs_uncached_writedata_release); > goto restart_loop; > } > } > -- > 2.17.1 >
The similar concepts applies for async reads as well.
-- Best regards, Pavel Shilovsky
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