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b=nN1NXCIgrxJ4wk4bcHMhmOuYrCKibErARAw+zOQjDHHFuOK18Brb1h1CQ5hmnTp8V KAyuHnkpDtG87QBRy9XwJlthDqNWBY202bxVt1qqw99Wzobz5thZ096hR0glKhIjII /ZA3UnhDf+X4rBLnCVp0MRl2Leq42RY0Kcie0wqnm4FzsG4U61FM3ZRq+0+x7gknv3 FzZKNTgibcdo9cf0/5GAfT8k1ONMZ9XozEApa5Sh4ftMjfeOgROuZcus0jAnRg5D/A kaXLd5qcq5VRrPOpsLSKYA5EOUNKK0ercajIivXck4U0VWWp1wDJfnDoM1SgBdANjJ cZ6W8T227w59w== Date: Thu, 14 Nov 2024 09:39:31 -0700 From: Nathan Chancellor To: David Howells , Christian Brauner Cc: Steve French , Matthew Wilcox , Jeff Layton , Gao Xiang , Dominique Martinet , Marc Dionne , Paulo Alcantara , Shyam Prasad N , Tom Talpey , Eric Van Hensbergen , Ilya Dryomov , netfs@lists.linux.dev, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs@lists.linux.dev, linux-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 28/33] netfs: Change the read result collector to only use one work item Message-ID: <20241114163931.GA1928968@thelio-3990X> References: <20241108173236.1382366-1-dhowells@redhat.com> <20241108173236.1382366-29-dhowells@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241108173236.1382366-29-dhowells@redhat.com> X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 1BE1D180008 X-Stat-Signature: ddk5ecw3ujd63s86wb6g8moizz7ekfnb X-HE-Tag: 1731602343-205030 X-HE-Meta: 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 Of47bdM4 yIUoqYWJnOe9Rhy8s1PT5dDZE+uG3kjUV4syFcIqnjp6dHSY2i1czRi0p96HykBZr0eK212MMUoFqBAItuOSMZU3o8P29jHuhxYZY/47+8lbtQ/btWDl88kzksK5flBlpunwvVde52SawJWoJMZs2PONbolJ0aP8cFqqKjlla/zOHU/vBldPn5l+eDoGI9hF4rvyfhIpbmS0ITWyxpzkIq4XWG1LWZcW/1MiQJxeounyiJIIBYaNKEHsVddSC+mlpwQRxIQYPViX77SiHXyvbCv8U2qtdqQ6XjGd72nsN2R7cbqQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi David, On Fri, Nov 08, 2024 at 05:32:29PM +0000, David Howells wrote: ... > diff --git a/fs/netfs/read_retry.c b/fs/netfs/read_retry.c > index 264f3cb6a7dc..8ca0558570c1 100644 > --- a/fs/netfs/read_retry.c > +++ b/fs/netfs/read_retry.c > @@ -12,15 +12,8 @@ > static void netfs_reissue_read(struct netfs_io_request *rreq, > struct netfs_io_subrequest *subreq) > { > - struct iov_iter *io_iter = &subreq->io_iter; > - > - if (iov_iter_is_folioq(io_iter)) { > - subreq->curr_folioq = (struct folio_queue *)io_iter->folioq; > - subreq->curr_folioq_slot = io_iter->folioq_slot; > - subreq->curr_folio_order = subreq->curr_folioq->orders[subreq->curr_folioq_slot]; > - } > - > - atomic_inc(&rreq->nr_outstanding); > + __clear_bit(NETFS_SREQ_MADE_PROGRESS, &subreq->flags); > + __set_bit(NETFS_SREQ_RETRYING, &subreq->flags); > __set_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags); > netfs_get_subrequest(subreq, netfs_sreq_trace_get_resubmit); > subreq->rreq->netfs_ops->issue_read(subreq); > @@ -33,13 +26,12 @@ static void netfs_reissue_read(struct netfs_io_request *rreq, > static void netfs_retry_read_subrequests(struct netfs_io_request *rreq) > { > struct netfs_io_subrequest *subreq; > - struct netfs_io_stream *stream0 = &rreq->io_streams[0]; > - LIST_HEAD(sublist); > - LIST_HEAD(queue); > + struct netfs_io_stream *stream = &rreq->io_streams[0]; > + struct list_head *next; > > _enter("R=%x", rreq->debug_id); > > - if (list_empty(&rreq->subrequests)) > + if (list_empty(&stream->subrequests)) > return; > > if (rreq->netfs_ops->retry_request) > @@ -52,7 +44,7 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq) > !test_bit(NETFS_RREQ_COPY_TO_CACHE, &rreq->flags)) { > struct netfs_io_subrequest *subreq; > > - list_for_each_entry(subreq, &rreq->subrequests, rreq_link) { > + list_for_each_entry(subreq, &stream->subrequests, rreq_link) { > if (test_bit(NETFS_SREQ_FAILED, &subreq->flags)) > break; > if (__test_and_clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags)) { > @@ -73,48 +65,44 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq) > * populating with smaller subrequests. In the event that the subreq > * we just launched finishes before we insert the next subreq, it'll > * fill in rreq->prev_donated instead. > - > + * > * Note: Alternatively, we could split the tail subrequest right before > * we reissue it and fix up the donations under lock. > */ > - list_splice_init(&rreq->subrequests, &queue); > + next = stream->subrequests.next; > > do { > - struct netfs_io_subrequest *from; > + struct netfs_io_subrequest *subreq = NULL, *from, *to, *tmp; > struct iov_iter source; > unsigned long long start, len; > - size_t part, deferred_next_donated = 0; > + size_t part; > bool boundary = false; > > /* Go through the subreqs and find the next span of contiguous > * buffer that we then rejig (cifs, for example, needs the > * rsize renegotiating) and reissue. > */ > - from = list_first_entry(&queue, struct netfs_io_subrequest, rreq_link); > - list_move_tail(&from->rreq_link, &sublist); > + from = list_entry(next, struct netfs_io_subrequest, rreq_link); > + to = from; > start = from->start + from->transferred; > len = from->len - from->transferred; > > - _debug("from R=%08x[%x] s=%llx ctl=%zx/%zx/%zx", > + _debug("from R=%08x[%x] s=%llx ctl=%zx/%zx", > rreq->debug_id, from->debug_index, > - from->start, from->consumed, from->transferred, from->len); > + from->start, from->transferred, from->len); > > if (test_bit(NETFS_SREQ_FAILED, &from->flags) || > !test_bit(NETFS_SREQ_NEED_RETRY, &from->flags)) > goto abandon; > > - deferred_next_donated = from->next_donated; > - while ((subreq = list_first_entry_or_null( > - &queue, struct netfs_io_subrequest, rreq_link))) { > - if (subreq->start != start + len || > - subreq->transferred > 0 || > + list_for_each_continue(next, &stream->subrequests) { > + subreq = list_entry(next, struct netfs_io_subrequest, rreq_link); > + if (subreq->start + subreq->transferred != start + len || > + test_bit(NETFS_SREQ_BOUNDARY, &subreq->flags) || > !test_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags)) > break; > - list_move_tail(&subreq->rreq_link, &sublist); > - len += subreq->len; > - deferred_next_donated = subreq->next_donated; > - if (test_bit(NETFS_SREQ_BOUNDARY, &subreq->flags)) > - break; > + to = subreq; > + len += to->len; > } > > _debug(" - range: %llx-%llx %llx", start, start + len - 1, len); > @@ -127,36 +115,28 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq) > source.count = len; > > /* Work through the sublist. */ > - while ((subreq = list_first_entry_or_null( > - &sublist, struct netfs_io_subrequest, rreq_link))) { > - list_del(&subreq->rreq_link); > - > + subreq = from; > + list_for_each_entry_from(subreq, &stream->subrequests, rreq_link) { > + if (!len) > + break; > subreq->source = NETFS_DOWNLOAD_FROM_SERVER; > subreq->start = start - subreq->transferred; > subreq->len = len + subreq->transferred; > - stream0->sreq_max_len = subreq->len; > - > __clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags); > __set_bit(NETFS_SREQ_RETRYING, &subreq->flags); > - > - spin_lock(&rreq->lock); > - list_add_tail(&subreq->rreq_link, &rreq->subrequests); > - subreq->prev_donated += rreq->prev_donated; > - rreq->prev_donated = 0; > trace_netfs_sreq(subreq, netfs_sreq_trace_retry); > - spin_unlock(&rreq->lock); > - > - BUG_ON(!len); > > /* Renegotiate max_len (rsize) */ > + stream->sreq_max_len = subreq->len; > if (rreq->netfs_ops->prepare_read(subreq) < 0) { > trace_netfs_sreq(subreq, netfs_sreq_trace_reprep_failed); > __set_bit(NETFS_SREQ_FAILED, &subreq->flags); > + goto abandon; > } > > - part = umin(len, stream0->sreq_max_len); > - if (unlikely(rreq->io_streams[0].sreq_max_segs)) > - part = netfs_limit_iter(&source, 0, part, stream0->sreq_max_segs); > + part = umin(len, stream->sreq_max_len); > + if (unlikely(stream->sreq_max_segs)) > + part = netfs_limit_iter(&source, 0, part, stream->sreq_max_segs); > subreq->len = subreq->transferred + part; > subreq->io_iter = source; > iov_iter_truncate(&subreq->io_iter, part); > @@ -166,58 +146,106 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq) > if (!len) { > if (boundary) > __set_bit(NETFS_SREQ_BOUNDARY, &subreq->flags); > - subreq->next_donated = deferred_next_donated; > } else { > __clear_bit(NETFS_SREQ_BOUNDARY, &subreq->flags); > - subreq->next_donated = 0; > } > > + netfs_get_subrequest(subreq, netfs_sreq_trace_get_resubmit); > netfs_reissue_read(rreq, subreq); > - if (!len) > + if (subreq == to) > break; > - > - /* If we ran out of subrequests, allocate another. */ > - if (list_empty(&sublist)) { > - subreq = netfs_alloc_subrequest(rreq); > - if (!subreq) > - goto abandon; > - subreq->source = NETFS_DOWNLOAD_FROM_SERVER; > - subreq->start = start; > - > - /* We get two refs, but need just one. */ > - netfs_put_subrequest(subreq, false, netfs_sreq_trace_new); > - trace_netfs_sreq(subreq, netfs_sreq_trace_split); > - list_add_tail(&subreq->rreq_link, &sublist); > - } > } > > /* If we managed to use fewer subreqs, we can discard the > - * excess. > + * excess; if we used the same number, then we're done. > */ > - while ((subreq = list_first_entry_or_null( > - &sublist, struct netfs_io_subrequest, rreq_link))) { > - trace_netfs_sreq(subreq, netfs_sreq_trace_discard); > - list_del(&subreq->rreq_link); > - netfs_put_subrequest(subreq, false, netfs_sreq_trace_put_done); > + if (!len) { > + if (subreq == to) > + continue; > + list_for_each_entry_safe_from(subreq, tmp, > + &stream->subrequests, rreq_link) { > + trace_netfs_sreq(subreq, netfs_sreq_trace_discard); > + list_del(&subreq->rreq_link); > + netfs_put_subrequest(subreq, false, netfs_sreq_trace_put_done); > + if (subreq == to) > + break; > + } > + continue; > } > > - } while (!list_empty(&queue)); > + /* We ran out of subrequests, so we need to allocate some more > + * and insert them after. > + */ > + do { > + subreq = netfs_alloc_subrequest(rreq); > + if (!subreq) { > + subreq = to; > + goto abandon_after; > + } > + subreq->source = NETFS_DOWNLOAD_FROM_SERVER; > + subreq->start = start; > + subreq->len = len; > + subreq->debug_index = atomic_inc_return(&rreq->subreq_counter); > + subreq->stream_nr = stream->stream_nr; > + __set_bit(NETFS_SREQ_RETRYING, &subreq->flags); > + > + trace_netfs_sreq_ref(rreq->debug_id, subreq->debug_index, > + refcount_read(&subreq->ref), > + netfs_sreq_trace_new); > + netfs_get_subrequest(subreq, netfs_sreq_trace_get_resubmit); > + > + list_add(&subreq->rreq_link, &to->rreq_link); > + to = list_next_entry(to, rreq_link); > + trace_netfs_sreq(subreq, netfs_sreq_trace_retry); > + > + stream->sreq_max_len = umin(len, rreq->rsize); > + stream->sreq_max_segs = 0; > + if (unlikely(stream->sreq_max_segs)) > + part = netfs_limit_iter(&source, 0, part, stream->sreq_max_segs); > + > + netfs_stat(&netfs_n_rh_download); > + if (rreq->netfs_ops->prepare_read(subreq) < 0) { > + trace_netfs_sreq(subreq, netfs_sreq_trace_reprep_failed); > + __set_bit(NETFS_SREQ_FAILED, &subreq->flags); > + goto abandon; > + } > + > + part = umin(len, stream->sreq_max_len); > + subreq->len = subreq->transferred + part; > + subreq->io_iter = source; > + iov_iter_truncate(&subreq->io_iter, part); > + iov_iter_advance(&source, part); > + > + len -= part; > + start += part; > + if (!len && boundary) { > + __set_bit(NETFS_SREQ_BOUNDARY, &to->flags); > + boundary = false; > + } > + > + netfs_reissue_read(rreq, subreq); > + } while (len); > + > + } while (!list_is_head(next, &stream->subrequests)); > > return; > > - /* If we hit ENOMEM, fail all remaining subrequests */ > + /* If we hit an error, fail all remaining incomplete subrequests */ > +abandon_after: > + if (list_is_last(&subreq->rreq_link, &stream->subrequests)) > + return; This change as commit 1bd9011ee163 ("netfs: Change the read result collector to only use one work item") in next-20241114 causes a clang warning: fs/netfs/read_retry.c:235:20: error: variable 'subreq' is uninitialized when used here [-Werror,-Wuninitialized] 235 | if (list_is_last(&subreq->rreq_link, &stream->subrequests)) | ^~~~~~ fs/netfs/read_retry.c:28:36: note: initialize the variable 'subreq' to silence this warning 28 | struct netfs_io_subrequest *subreq; | ^ | = NULL May be a shadowing issue, as adding KCFLAGS=-Wshadow shows: fs/netfs/read_retry.c:75:31: error: declaration shadows a local variable [-Werror,-Wshadow] 75 | struct netfs_io_subrequest *subreq = NULL, *from, *to, *tmp; | ^ fs/netfs/read_retry.c:28:30: note: previous declaration is here 28 | struct netfs_io_subrequest *subreq; | ^ Cheers, Nathan > + subreq = list_next_entry(subreq, rreq_link); > abandon: > - list_splice_init(&sublist, &queue); > - list_for_each_entry(subreq, &queue, rreq_link) { > - if (!subreq->error) > - subreq->error = -ENOMEM; > - __clear_bit(NETFS_SREQ_FAILED, &subreq->flags); > + list_for_each_entry_from(subreq, &stream->subrequests, rreq_link) { > + if (!subreq->error && > + !test_bit(NETFS_SREQ_FAILED, &subreq->flags) && > + !test_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags)) > + continue; > + subreq->error = -ENOMEM; > + __set_bit(NETFS_SREQ_FAILED, &subreq->flags); > __clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags); > __clear_bit(NETFS_SREQ_RETRYING, &subreq->flags); > } > - spin_lock(&rreq->lock); > - list_splice_tail_init(&queue, &rreq->subrequests); > - spin_unlock(&rreq->lock); > } > > /* > @@ -225,14 +253,19 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq) > */ > void netfs_retry_reads(struct netfs_io_request *rreq) > { > - trace_netfs_rreq(rreq, netfs_rreq_trace_resubmit); > + struct netfs_io_subrequest *subreq; > + struct netfs_io_stream *stream = &rreq->io_streams[0]; > > - atomic_inc(&rreq->nr_outstanding); > + /* Wait for all outstanding I/O to quiesce before performing retries as > + * we may need to renegotiate the I/O sizes. > + */ > + list_for_each_entry(subreq, &stream->subrequests, rreq_link) { > + wait_on_bit(&subreq->flags, NETFS_SREQ_IN_PROGRESS, > + TASK_UNINTERRUPTIBLE); > + } > > + trace_netfs_rreq(rreq, netfs_rreq_trace_resubmit); > netfs_retry_read_subrequests(rreq); > - > - if (atomic_dec_and_test(&rreq->nr_outstanding)) > - netfs_rreq_terminated(rreq); > } > > /*