| Message ID | 1376938.1613429183@warthog.procyon.org.uk |
|---|---|
| State | New |
| Headers | show |
| Series | Network fs helper library & fscache kiocb API [ver #3] | expand |
On Mon, Feb 15, 2021 at 10:46:23PM +0000, David Howells wrote: > The in_softirq() in netfs_rreq_terminated() works fine for the cache being > on a normal disk, as the completion handlers may get called in softirq > context, but for an NVMe drive, the completion handler may get called in > IRQ context. > > Fix to use in_interrupt() instead of in_softirq() throughout the read > helpers, particularly when deciding whether to punt code that might sleep > off to a worker thread. We must not use either check, as they all are unreliable especially for PREEMPT-RT.
On 2021-02-16 09:42:30 [+0100], Christoph Hellwig wrote: > On Mon, Feb 15, 2021 at 10:46:23PM +0000, David Howells wrote: > > The in_softirq() in netfs_rreq_terminated() works fine for the cache being > > on a normal disk, as the completion handlers may get called in softirq > > context, but for an NVMe drive, the completion handler may get called in > > IRQ context. > > > > Fix to use in_interrupt() instead of in_softirq() throughout the read > > helpers, particularly when deciding whether to punt code that might sleep > > off to a worker thread. > > We must not use either check, as they all are unreliable especially > for PREEMPT-RT. Yes, please. I try to cleanup the users one by one https://lore.kernel.org/r/20200914204209.256266093@linutronix.de/ https://lore.kernel.org/amd-gfx/20210209124439.408140-1-bigeasy@linutronix.de/ Sebastian
Christoph Hellwig <hch@lst.de> wrote: > On Mon, Feb 15, 2021 at 10:46:23PM +0000, David Howells wrote: > > The in_softirq() in netfs_rreq_terminated() works fine for the cache being > > on a normal disk, as the completion handlers may get called in softirq > > context, but for an NVMe drive, the completion handler may get called in > > IRQ context. > > > > Fix to use in_interrupt() instead of in_softirq() throughout the read > > helpers, particularly when deciding whether to punt code that might sleep > > off to a worker thread. > > We must not use either check, as they all are unreliable especially > for PREEMPT-RT. Is there a better way to do it? The intent is to process the assessment phase in the calling thread's context if possible rather than bumping over to a worker thread. For synchronous I/O, for example, that's done in the caller's thread. Maybe that's the answer - if it's known to be asynchronous, I have to punt, but otherwise don't have to. David
On Tue, Feb 16, 2021 at 09:29:31AM +0000, David Howells wrote: > Is there a better way to do it? The intent is to process the assessment phase > in the calling thread's context if possible rather than bumping over to a > worker thread. For synchronous I/O, for example, that's done in the caller's > thread. Maybe that's the answer - if it's known to be asynchronous, I have to > punt, but otherwise don't have to. Yes, i think you want an explicit flag instead.
On Thu, Feb 18, 2021 at 10:03 AM David Howells <dhowells@redhat.com> wrote: > > Christoph Hellwig <hch@lst.de> wrote: > > > On Tue, Feb 16, 2021 at 09:29:31AM +0000, David Howells wrote: > > > Is there a better way to do it? The intent is to process the assessment > > > phase in the calling thread's context if possible rather than bumping over > > > to a worker thread. For synchronous I/O, for example, that's done in the > > > caller's thread. Maybe that's the answer - if it's known to be > > > asynchronous, I have to punt, but otherwise don't have to. > > > > Yes, i think you want an explicit flag instead. > > How about the attached instead? > > David > --- > commit 29b3e9eed616db01f15c7998c062b4e501ea6582 > Author: David Howells <dhowells@redhat.com> > Date: Mon Feb 15 21:56:43 2021 +0000 > > netfs: Pass flag rather than use in_softirq() > > The in_softirq() in netfs_rreq_terminated() works fine for the cache being > on a normal disk, as the completion handlers may get called in softirq > context, but for an NVMe drive, the completion handler may get called in > IRQ context. > > Fix to pass a flag to netfs_subreq_terminated() to indicate whether we > think the function isn't being called from a context in which we can do > allocations, waits and I/O submissions (such as softirq or interrupt > context). If this flag is set, netfs lib has to punt to a worker thread to > handle anything like that. > > The symptom involves warnings like the following appearing and the kernel > hanging: > > WARNING: CPU: 0 PID: 0 at kernel/softirq.c:175 __local_bh_enable_ip+0x35/0x50 > ... > RIP: 0010:__local_bh_enable_ip+0x35/0x50 > ... > Call Trace: > <IRQ> > rxrpc_kernel_begin_call+0x7d/0x1b0 [rxrpc] > ? afs_rx_new_call+0x40/0x40 [kafs] > ? afs_alloc_call+0x28/0x120 [kafs] > afs_make_call+0x120/0x510 [kafs] > ? afs_rx_new_call+0x40/0x40 [kafs] > ? afs_alloc_flat_call+0xba/0x100 [kafs] > ? __kmalloc+0x167/0x2f0 > ? afs_alloc_flat_call+0x9b/0x100 [kafs] > afs_wait_for_operation+0x2d/0x200 [kafs] > afs_do_sync_operation+0x16/0x20 [kafs] > afs_req_issue_op+0x8c/0xb0 [kafs] > netfs_rreq_assess+0x125/0x7d0 [netfs] > ? cachefiles_end_operation+0x40/0x40 [cachefiles] > netfs_subreq_terminated+0x117/0x220 [netfs] > cachefiles_read_complete+0x21/0x60 [cachefiles] > iomap_dio_bio_end_io+0xdd/0x110 > blk_update_request+0x20a/0x380 > blk_mq_end_request+0x1c/0x120 > nvme_process_cq+0x159/0x1f0 [nvme] > nvme_irq+0x10/0x20 [nvme] > __handle_irq_event_percpu+0x37/0x150 > handle_irq_event+0x49/0xb0 > handle_edge_irq+0x7c/0x200 > asm_call_irq_on_stack+0xf/0x20 > </IRQ> > common_interrupt+0xad/0x120 > asm_common_interrupt+0x1e/0x40 > ... > > Reported-by: Marc Dionne <marc.dionne@auristor.com> > Signed-off-by: David Howells <dhowells@redhat.com> > cc: Matthew Wilcox <willy@infradead.org> > cc: linux-mm@kvack.org > cc: linux-cachefs@redhat.com > cc: linux-afs@lists.infradead.org > cc: linux-nfs@vger.kernel.org > cc: linux-cifs@vger.kernel.org > cc: ceph-devel@vger.kernel.org > cc: v9fs-developer@lists.sourceforge.net > cc: linux-fsdevel@vger.kernel.org > > diff --git a/fs/afs/file.c b/fs/afs/file.c > index 8f28d4f4cfd7..6dcdbbfb48e2 100644 > --- a/fs/afs/file.c > +++ b/fs/afs/file.c > @@ -223,7 +223,7 @@ static void afs_fetch_data_notify(struct afs_operation *op) > > if (subreq) { > __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags); > - netfs_subreq_terminated(subreq, error ?: req->actual_len); > + netfs_subreq_terminated(subreq, error ?: req->actual_len, false); > req->subreq = NULL; > } else if (req->done) { > req->done(req); > @@ -289,7 +289,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq) > > fsreq = afs_alloc_read(GFP_NOFS); > if (!fsreq) > - return netfs_subreq_terminated(subreq, -ENOMEM); > + return netfs_subreq_terminated(subreq, -ENOMEM, false); > > fsreq->subreq = subreq; > fsreq->pos = subreq->start + subreq->transferred; > @@ -304,7 +304,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq) > > ret = afs_fetch_data(fsreq->vnode, fsreq); > if (ret < 0) > - return netfs_subreq_terminated(subreq, ret); > + return netfs_subreq_terminated(subreq, ret, false); > } > > static int afs_symlink_readpage(struct page *page) > diff --git a/fs/cachefiles/rdwr2.c b/fs/cachefiles/rdwr2.c > index 4cea5a2a2d6e..40668bfe6688 100644 > --- a/fs/cachefiles/rdwr2.c > +++ b/fs/cachefiles/rdwr2.c > @@ -23,6 +23,7 @@ struct cachefiles_kiocb { > }; > netfs_io_terminated_t term_func; > void *term_func_priv; > + bool was_async; > }; > > static inline void cachefiles_put_kiocb(struct cachefiles_kiocb *ki) > @@ -43,10 +44,9 @@ static void cachefiles_read_complete(struct kiocb *iocb, long ret, long ret2) > _enter("%ld,%ld", ret, ret2); > > if (ki->term_func) { > - if (ret < 0) > - ki->term_func(ki->term_func_priv, ret); > - else > - ki->term_func(ki->term_func_priv, ki->skipped + ret); > + if (ret >= 0) > + ret += ki->skipped; > + ki->term_func(ki->term_func_priv, ret, ki->was_async); > } > > cachefiles_put_kiocb(ki); > @@ -114,6 +114,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres, > ki->skipped = skipped; > ki->term_func = term_func; > ki->term_func_priv = term_func_priv; > + ki->was_async = true; > > if (ki->term_func) > ki->iocb.ki_complete = cachefiles_read_complete; > @@ -141,6 +142,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres, > ret = -EINTR; > fallthrough; > default: > + ki->was_async = false; > cachefiles_read_complete(&ki->iocb, ret, 0); > if (ret > 0) > ret = 0; > @@ -156,7 +158,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres, > kfree(ki); > presubmission_error: > if (term_func) > - term_func(term_func_priv, ret < 0 ? ret : skipped); > + term_func(term_func_priv, ret < 0 ? ret : skipped, false); > return ret; > } > > @@ -175,7 +177,7 @@ static void cachefiles_write_complete(struct kiocb *iocb, long ret, long ret2) > __sb_end_write(inode->i_sb, SB_FREEZE_WRITE); > > if (ki->term_func) > - ki->term_func(ki->term_func_priv, ret); > + ki->term_func(ki->term_func_priv, ret, ki->was_async); > > cachefiles_put_kiocb(ki); > } > @@ -214,6 +216,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres, > ki->len = len; > ki->term_func = term_func; > ki->term_func_priv = term_func_priv; > + ki->was_async = true; > > if (ki->term_func) > ki->iocb.ki_complete = cachefiles_write_complete; > @@ -250,6 +253,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres, > ret = -EINTR; > /* Fall through */ > default: > + ki->was_async = false; > cachefiles_write_complete(&ki->iocb, ret, 0); > if (ret > 0) > ret = 0; > @@ -265,7 +269,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres, > kfree(ki); > presubmission_error: > if (term_func) > - term_func(term_func_priv, -ENOMEM); > + term_func(term_func_priv, -ENOMEM, false); > return -ENOMEM; > } > > diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c > index 0dd64d31eff6..dcfd805d168e 100644 > --- a/fs/ceph/addr.c > +++ b/fs/ceph/addr.c > @@ -221,7 +221,7 @@ static void finish_netfs_read(struct ceph_osd_request *req) > if (err >= 0 && err < subreq->len) > __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags); > > - netfs_subreq_terminated(subreq, err); > + netfs_subreq_terminated(subreq, err, true); > > num_pages = calc_pages_for(osd_data->alignment, osd_data->length); > ceph_put_page_vector(osd_data->pages, num_pages, false); > @@ -276,7 +276,7 @@ static void ceph_netfs_issue_op(struct netfs_read_subrequest *subreq) > out: > ceph_osdc_put_request(req); > if (err) > - netfs_subreq_terminated(subreq, err); > + netfs_subreq_terminated(subreq, err, false); > dout("%s: result %d\n", __func__, err); > } > > diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c > index 9191a3617d91..5f5de8278499 100644 > --- a/fs/netfs/read_helper.c > +++ b/fs/netfs/read_helper.c > @@ -29,12 +29,13 @@ module_param_named(debug, netfs_debug, uint, S_IWUSR | S_IRUGO); > MODULE_PARM_DESC(netfs_debug, "Netfs support debugging mask"); > > static void netfs_rreq_work(struct work_struct *); > -static void __netfs_put_subrequest(struct netfs_read_subrequest *); > +static void __netfs_put_subrequest(struct netfs_read_subrequest *, bool); > > -static void netfs_put_subrequest(struct netfs_read_subrequest *subreq) > +static void netfs_put_subrequest(struct netfs_read_subrequest *subreq, > + bool was_async) > { > if (refcount_dec_and_test(&subreq->usage)) > - __netfs_put_subrequest(subreq); > + __netfs_put_subrequest(subreq, was_async); > } > > static struct netfs_read_request *netfs_alloc_read_request( > @@ -67,7 +68,8 @@ static void netfs_get_read_request(struct netfs_read_request *rreq) > refcount_inc(&rreq->usage); > } > > -static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq) > +static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq, > + bool was_async) > { > struct netfs_read_subrequest *subreq; > > @@ -75,7 +77,7 @@ static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq) > subreq = list_first_entry(&rreq->subrequests, > struct netfs_read_subrequest, rreq_link); > list_del(&subreq->rreq_link); > - netfs_put_subrequest(subreq); > + netfs_put_subrequest(subreq, was_async); > } > } > > @@ -83,7 +85,7 @@ static void netfs_free_read_request(struct work_struct *work) > { > struct netfs_read_request *rreq = > container_of(work, struct netfs_read_request, work); > - netfs_rreq_clear_subreqs(rreq); > + netfs_rreq_clear_subreqs(rreq, false); > if (rreq->netfs_priv) > rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv); > trace_netfs_rreq(rreq, netfs_rreq_trace_free); > @@ -93,10 +95,10 @@ static void netfs_free_read_request(struct work_struct *work) > netfs_stat_d(&netfs_n_rh_rreq); > } > > -static void netfs_put_read_request(struct netfs_read_request *rreq) > +static void netfs_put_read_request(struct netfs_read_request *rreq, bool was_async) > { > if (refcount_dec_and_test(&rreq->usage)) { > - if (in_softirq()) { > + if (was_async) { > rreq->work.func = netfs_free_read_request; > if (!queue_work(system_unbound_wq, &rreq->work)) > BUG(); > @@ -131,12 +133,15 @@ static void netfs_get_read_subrequest(struct netfs_read_subrequest *subreq) > refcount_inc(&subreq->usage); > } > > -static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq) > +static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq, > + bool was_async) > { > + struct netfs_read_request *rreq = subreq->rreq; > + > trace_netfs_sreq(subreq, netfs_sreq_trace_free); > - netfs_put_read_request(subreq->rreq); > kfree(subreq); > netfs_stat_d(&netfs_n_rh_sreq); > + netfs_put_read_request(rreq, was_async); > } > > /* > @@ -152,11 +157,12 @@ static void netfs_clear_unread(struct netfs_read_subrequest *subreq) > iov_iter_zero(iov_iter_count(&iter), &iter); > } > > -static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error) > +static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error, > + bool was_async) > { > struct netfs_read_subrequest *subreq = priv; > > - netfs_subreq_terminated(subreq, transferred_or_error); > + netfs_subreq_terminated(subreq, transferred_or_error, was_async); > } > > /* > @@ -186,7 +192,7 @@ static void netfs_fill_with_zeroes(struct netfs_read_request *rreq, > { > netfs_stat(&netfs_n_rh_zero); > __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags); > - netfs_subreq_terminated(subreq, 0); > + netfs_subreq_terminated(subreq, 0, false); > } > > /* > @@ -215,11 +221,11 @@ static void netfs_read_from_server(struct netfs_read_request *rreq, > /* > * Release those waiting. > */ > -static void netfs_rreq_completed(struct netfs_read_request *rreq) > +static void netfs_rreq_completed(struct netfs_read_request *rreq, bool was_async) > { > trace_netfs_rreq(rreq, netfs_rreq_trace_done); > - netfs_rreq_clear_subreqs(rreq); > - netfs_put_read_request(rreq); > + netfs_rreq_clear_subreqs(rreq, was_async); > + netfs_put_read_request(rreq, was_async); > } > > /* > @@ -228,7 +234,8 @@ static void netfs_rreq_completed(struct netfs_read_request *rreq) > * > * May be called in softirq mode and we inherit a ref from the caller. > */ > -static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq) > +static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq, > + bool was_async) > { > struct netfs_read_subrequest *subreq; > struct pagevec pvec; > @@ -258,10 +265,11 @@ static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq) > } > > rcu_read_unlock(); > - netfs_rreq_completed(rreq); > + netfs_rreq_completed(rreq, was_async); > } > > -static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error) > +static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error, > + bool was_async) > { > struct netfs_read_subrequest *subreq = priv; > struct netfs_read_request *rreq = subreq->rreq; > @@ -278,9 +286,9 @@ static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error) > > /* If we decrement nr_wr_ops to 0, the ref belongs to us. */ > if (atomic_dec_and_test(&rreq->nr_wr_ops)) > - netfs_rreq_unmark_after_write(rreq); > + netfs_rreq_unmark_after_write(rreq, was_async); > > - netfs_put_subrequest(subreq); > + netfs_put_subrequest(subreq, was_async); > } > > /* > @@ -304,7 +312,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq) > list_for_each_entry_safe(subreq, p, &rreq->subrequests, rreq_link) { > if (!test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags)) { > list_del_init(&subreq->rreq_link); > - netfs_put_subrequest(subreq); > + netfs_put_subrequest(subreq, false); > } > } > > @@ -324,7 +332,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq) > subreq->len += next->len; > subreq->len = round_up(subreq->len, PAGE_SIZE); > list_del_init(&next->rreq_link); > - netfs_put_subrequest(next); > + netfs_put_subrequest(next, false); > } > > iov_iter_xarray(&iter, WRITE, &rreq->mapping->i_pages, > @@ -340,7 +348,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq) > > /* If we decrement nr_wr_ops to 0, the usage ref belongs to us. */ > if (atomic_dec_and_test(&rreq->nr_wr_ops)) > - netfs_rreq_unmark_after_write(rreq); > + netfs_rreq_unmark_after_write(rreq, false); > } > > static void netfs_rreq_write_to_cache_work(struct work_struct *work) > @@ -351,9 +359,10 @@ static void netfs_rreq_write_to_cache_work(struct work_struct *work) > netfs_rreq_do_write_to_cache(rreq); > } > > -static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq) > +static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq, > + bool was_async) > { > - if (in_softirq()) { > + if (was_async) { > rreq->work.func = netfs_rreq_write_to_cache_work; > if (!queue_work(system_unbound_wq, &rreq->work)) > BUG(); > @@ -479,7 +488,7 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq) > { > struct netfs_read_subrequest *subreq; > > - WARN_ON(in_softirq()); > + WARN_ON(in_interrupt()); > > trace_netfs_rreq(rreq, netfs_rreq_trace_resubmit); > > @@ -538,7 +547,7 @@ static void netfs_rreq_is_still_valid(struct netfs_read_request *rreq) > * Note that we could be in an ordinary kernel thread, on a workqueue or in > * softirq context at this point. We inherit a ref from the caller. > */ > -static void netfs_rreq_assess(struct netfs_read_request *rreq) > +static void netfs_rreq_assess(struct netfs_read_request *rreq, bool was_async) > { > trace_netfs_rreq(rreq, netfs_rreq_trace_assess); > > @@ -558,30 +567,31 @@ static void netfs_rreq_assess(struct netfs_read_request *rreq) > wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS); > > if (test_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags)) > - return netfs_rreq_write_to_cache(rreq); > + return netfs_rreq_write_to_cache(rreq, was_async); > > - netfs_rreq_completed(rreq); > + netfs_rreq_completed(rreq, was_async); > } > > static void netfs_rreq_work(struct work_struct *work) > { > struct netfs_read_request *rreq = > container_of(work, struct netfs_read_request, work); > - netfs_rreq_assess(rreq); > + netfs_rreq_assess(rreq, false); > } > > /* > * Handle the completion of all outstanding I/O operations on a read request. > * We inherit a ref from the caller. > */ > -static void netfs_rreq_terminated(struct netfs_read_request *rreq) > +static void netfs_rreq_terminated(struct netfs_read_request *rreq, > + bool was_async) > { > if (test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags) && > - in_softirq()) { > + was_async) { > if (!queue_work(system_unbound_wq, &rreq->work)) > BUG(); > } else { > - netfs_rreq_assess(rreq); > + netfs_rreq_assess(rreq, was_async); > } > } > > @@ -589,6 +599,7 @@ static void netfs_rreq_terminated(struct netfs_read_request *rreq) > * netfs_subreq_terminated - Note the termination of an I/O operation. > * @subreq: The I/O request that has terminated. > * @transferred_or_error: The amount of data transferred or an error code. > + * @was_async: The termination was asynchronous > * > * This tells the read helper that a contributory I/O operation has terminated, > * one way or another, and that it should integrate the results. > @@ -599,11 +610,12 @@ static void netfs_rreq_terminated(struct netfs_read_request *rreq) > * error code. The helper will look after reissuing I/O operations as > * appropriate and writing downloaded data to the cache. > * > - * This may be called from a softirq handler, so we want to avoid taking the > - * spinlock if we can. > + * If @was_async is true, the caller might be running in softirq or interrupt > + * context and we can't sleep. > */ > void netfs_subreq_terminated(struct netfs_read_subrequest *subreq, > - ssize_t transferred_or_error) > + ssize_t transferred_or_error, > + bool was_async) > { > struct netfs_read_request *rreq = subreq->rreq; > int u; > @@ -647,11 +659,11 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq, > /* If we decrement nr_rd_ops to 0, the ref belongs to us. */ > u = atomic_dec_return(&rreq->nr_rd_ops); > if (u == 0) > - netfs_rreq_terminated(rreq); > + netfs_rreq_terminated(rreq, was_async); > else if (u == 1) > wake_up_var(&rreq->nr_rd_ops); > > - netfs_put_subrequest(subreq); > + netfs_put_subrequest(subreq, was_async); > return; > > incomplete: > @@ -796,7 +808,7 @@ static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq, > > subreq_failed: > rreq->error = subreq->error; > - netfs_put_subrequest(subreq); > + netfs_put_subrequest(subreq, false); > return false; > } > > @@ -901,7 +913,7 @@ void netfs_readahead(struct readahead_control *ractl, > } while (rreq->submitted < rreq->len); > > if (rreq->submitted == 0) { > - netfs_put_read_request(rreq); > + netfs_put_read_request(rreq, false); > return; > } > > @@ -913,11 +925,11 @@ void netfs_readahead(struct readahead_control *ractl, > > /* If we decrement nr_rd_ops to 0, the ref belongs to us. */ > if (atomic_dec_and_test(&rreq->nr_rd_ops)) > - netfs_rreq_assess(rreq); > + netfs_rreq_assess(rreq, false); > return; > > cleanup_free: > - netfs_put_read_request(rreq); > + netfs_put_read_request(rreq, false); > return; > cleanup: > if (netfs_priv) > @@ -991,14 +1003,14 @@ int netfs_readpage(struct file *file, > */ > do { > wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1); > - netfs_rreq_assess(rreq); > + netfs_rreq_assess(rreq, false); > } while (test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags)); > > ret = rreq->error; > if (ret == 0 && rreq->submitted < rreq->len) > ret = -EIO; > out: > - netfs_put_read_request(rreq); > + netfs_put_read_request(rreq, false); > return ret; > } > EXPORT_SYMBOL(netfs_readpage); > @@ -1136,7 +1148,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping, > */ > for (;;) { > wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1); > - netfs_rreq_assess(rreq); > + netfs_rreq_assess(rreq, false); > if (!test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags)) > break; > cond_resched(); > @@ -1145,7 +1157,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping, > ret = rreq->error; > if (ret == 0 && rreq->submitted < rreq->len) > ret = -EIO; > - netfs_put_read_request(rreq); > + netfs_put_read_request(rreq, false); > if (ret < 0) > goto error; > > diff --git a/include/linux/netfs.h b/include/linux/netfs.h > index b2589b39feb8..c22b64db237d 100644 > --- a/include/linux/netfs.h > +++ b/include/linux/netfs.h > @@ -60,7 +60,8 @@ enum netfs_read_source { > NETFS_INVALID_READ, > } __mode(byte); > > -typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error); > +typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error, > + bool was_async); > > /* > * Resources required to do operations on a cache. > @@ -189,7 +190,7 @@ extern int netfs_write_begin(struct file *, struct address_space *, > const struct netfs_read_request_ops *, > void *); > > -extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t); > +extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t, bool); > extern void netfs_stats_show(struct seq_file *); > > #endif /* _LINUX_NETFS_H */ > > Looks good in testing. Tested-by: Marc Dionne <marc.dionne@auristor.com>
On Thu, Feb 18, 2021 at 10:03 AM David Howells <dhowells@redhat.com> wrote: > > Christoph Hellwig <hch@lst.de> wrote: > > > On Tue, Feb 16, 2021 at 09:29:31AM +0000, David Howells wrote: > > > Is there a better way to do it? The intent is to process the assessment > > > phase in the calling thread's context if possible rather than bumping over > > > to a worker thread. For synchronous I/O, for example, that's done in the > > > caller's thread. Maybe that's the answer - if it's known to be > > > asynchronous, I have to punt, but otherwise don't have to. > > > > Yes, i think you want an explicit flag instead. > > How about the attached instead? > > David > --- > commit 29b3e9eed616db01f15c7998c062b4e501ea6582 > Author: David Howells <dhowells@redhat.com> > Date: Mon Feb 15 21:56:43 2021 +0000 > > netfs: Pass flag rather than use in_softirq() > > The in_softirq() in netfs_rreq_terminated() works fine for the cache being > on a normal disk, as the completion handlers may get called in softirq > context, but for an NVMe drive, the completion handler may get called in > IRQ context. > > Fix to pass a flag to netfs_subreq_terminated() to indicate whether we > think the function isn't being called from a context in which we can do > allocations, waits and I/O submissions (such as softirq or interrupt > context). If this flag is set, netfs lib has to punt to a worker thread to > handle anything like that. > > The symptom involves warnings like the following appearing and the kernel > hanging: > > WARNING: CPU: 0 PID: 0 at kernel/softirq.c:175 __local_bh_enable_ip+0x35/0x50 > ... > RIP: 0010:__local_bh_enable_ip+0x35/0x50 > ... > Call Trace: > <IRQ> > rxrpc_kernel_begin_call+0x7d/0x1b0 [rxrpc] > ? afs_rx_new_call+0x40/0x40 [kafs] > ? afs_alloc_call+0x28/0x120 [kafs] > afs_make_call+0x120/0x510 [kafs] > ? afs_rx_new_call+0x40/0x40 [kafs] > ? afs_alloc_flat_call+0xba/0x100 [kafs] > ? __kmalloc+0x167/0x2f0 > ? afs_alloc_flat_call+0x9b/0x100 [kafs] > afs_wait_for_operation+0x2d/0x200 [kafs] > afs_do_sync_operation+0x16/0x20 [kafs] > afs_req_issue_op+0x8c/0xb0 [kafs] > netfs_rreq_assess+0x125/0x7d0 [netfs] > ? cachefiles_end_operation+0x40/0x40 [cachefiles] > netfs_subreq_terminated+0x117/0x220 [netfs] > cachefiles_read_complete+0x21/0x60 [cachefiles] > iomap_dio_bio_end_io+0xdd/0x110 > blk_update_request+0x20a/0x380 > blk_mq_end_request+0x1c/0x120 > nvme_process_cq+0x159/0x1f0 [nvme] > nvme_irq+0x10/0x20 [nvme] > __handle_irq_event_percpu+0x37/0x150 > handle_irq_event+0x49/0xb0 > handle_edge_irq+0x7c/0x200 > asm_call_irq_on_stack+0xf/0x20 > </IRQ> > common_interrupt+0xad/0x120 > asm_common_interrupt+0x1e/0x40 > ... > > Reported-by: Marc Dionne <marc.dionne@auristor.com> > Signed-off-by: David Howells <dhowells@redhat.com> > cc: Matthew Wilcox <willy@infradead.org> > cc: linux-mm@kvack.org > cc: linux-cachefs@redhat.com > cc: linux-afs@lists.infradead.org > cc: linux-nfs@vger.kernel.org > cc: linux-cifs@vger.kernel.org > cc: ceph-devel@vger.kernel.org > cc: v9fs-developer@lists.sourceforge.net > cc: linux-fsdevel@vger.kernel.org > > diff --git a/fs/afs/file.c b/fs/afs/file.c > index 8f28d4f4cfd7..6dcdbbfb48e2 100644 > --- a/fs/afs/file.c > +++ b/fs/afs/file.c > @@ -223,7 +223,7 @@ static void afs_fetch_data_notify(struct afs_operation *op) > > if (subreq) { > __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags); > - netfs_subreq_terminated(subreq, error ?: req->actual_len); > + netfs_subreq_terminated(subreq, error ?: req->actual_len, false); > req->subreq = NULL; > } else if (req->done) { > req->done(req); > @@ -289,7 +289,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq) > > fsreq = afs_alloc_read(GFP_NOFS); > if (!fsreq) > - return netfs_subreq_terminated(subreq, -ENOMEM); > + return netfs_subreq_terminated(subreq, -ENOMEM, false); > > fsreq->subreq = subreq; > fsreq->pos = subreq->start + subreq->transferred; > @@ -304,7 +304,7 @@ static void afs_req_issue_op(struct netfs_read_subrequest *subreq) > > ret = afs_fetch_data(fsreq->vnode, fsreq); > if (ret < 0) > - return netfs_subreq_terminated(subreq, ret); > + return netfs_subreq_terminated(subreq, ret, false); > } > > static int afs_symlink_readpage(struct page *page) > diff --git a/fs/cachefiles/rdwr2.c b/fs/cachefiles/rdwr2.c > index 4cea5a2a2d6e..40668bfe6688 100644 > --- a/fs/cachefiles/rdwr2.c > +++ b/fs/cachefiles/rdwr2.c > @@ -23,6 +23,7 @@ struct cachefiles_kiocb { > }; > netfs_io_terminated_t term_func; > void *term_func_priv; > + bool was_async; > }; > > static inline void cachefiles_put_kiocb(struct cachefiles_kiocb *ki) > @@ -43,10 +44,9 @@ static void cachefiles_read_complete(struct kiocb *iocb, long ret, long ret2) > _enter("%ld,%ld", ret, ret2); > > if (ki->term_func) { > - if (ret < 0) > - ki->term_func(ki->term_func_priv, ret); > - else > - ki->term_func(ki->term_func_priv, ki->skipped + ret); > + if (ret >= 0) > + ret += ki->skipped; > + ki->term_func(ki->term_func_priv, ret, ki->was_async); > } > > cachefiles_put_kiocb(ki); > @@ -114,6 +114,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres, > ki->skipped = skipped; > ki->term_func = term_func; > ki->term_func_priv = term_func_priv; > + ki->was_async = true; > > if (ki->term_func) > ki->iocb.ki_complete = cachefiles_read_complete; > @@ -141,6 +142,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres, > ret = -EINTR; > fallthrough; > default: > + ki->was_async = false; > cachefiles_read_complete(&ki->iocb, ret, 0); > if (ret > 0) > ret = 0; > @@ -156,7 +158,7 @@ static int cachefiles_read(struct netfs_cache_resources *cres, > kfree(ki); > presubmission_error: > if (term_func) > - term_func(term_func_priv, ret < 0 ? ret : skipped); > + term_func(term_func_priv, ret < 0 ? ret : skipped, false); > return ret; > } > > @@ -175,7 +177,7 @@ static void cachefiles_write_complete(struct kiocb *iocb, long ret, long ret2) > __sb_end_write(inode->i_sb, SB_FREEZE_WRITE); > > if (ki->term_func) > - ki->term_func(ki->term_func_priv, ret); > + ki->term_func(ki->term_func_priv, ret, ki->was_async); > > cachefiles_put_kiocb(ki); > } > @@ -214,6 +216,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres, > ki->len = len; > ki->term_func = term_func; > ki->term_func_priv = term_func_priv; > + ki->was_async = true; > > if (ki->term_func) > ki->iocb.ki_complete = cachefiles_write_complete; > @@ -250,6 +253,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres, > ret = -EINTR; > /* Fall through */ > default: > + ki->was_async = false; > cachefiles_write_complete(&ki->iocb, ret, 0); > if (ret > 0) > ret = 0; > @@ -265,7 +269,7 @@ static int cachefiles_write(struct netfs_cache_resources *cres, > kfree(ki); > presubmission_error: > if (term_func) > - term_func(term_func_priv, -ENOMEM); > + term_func(term_func_priv, -ENOMEM, false); > return -ENOMEM; > } > > diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c > index 0dd64d31eff6..dcfd805d168e 100644 > --- a/fs/ceph/addr.c > +++ b/fs/ceph/addr.c > @@ -221,7 +221,7 @@ static void finish_netfs_read(struct ceph_osd_request *req) > if (err >= 0 && err < subreq->len) > __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags); > > - netfs_subreq_terminated(subreq, err); > + netfs_subreq_terminated(subreq, err, true); > > num_pages = calc_pages_for(osd_data->alignment, osd_data->length); > ceph_put_page_vector(osd_data->pages, num_pages, false); > @@ -276,7 +276,7 @@ static void ceph_netfs_issue_op(struct netfs_read_subrequest *subreq) > out: > ceph_osdc_put_request(req); > if (err) > - netfs_subreq_terminated(subreq, err); > + netfs_subreq_terminated(subreq, err, false); > dout("%s: result %d\n", __func__, err); > } > > diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c > index 9191a3617d91..5f5de8278499 100644 > --- a/fs/netfs/read_helper.c > +++ b/fs/netfs/read_helper.c > @@ -29,12 +29,13 @@ module_param_named(debug, netfs_debug, uint, S_IWUSR | S_IRUGO); > MODULE_PARM_DESC(netfs_debug, "Netfs support debugging mask"); > > static void netfs_rreq_work(struct work_struct *); > -static void __netfs_put_subrequest(struct netfs_read_subrequest *); > +static void __netfs_put_subrequest(struct netfs_read_subrequest *, bool); > > -static void netfs_put_subrequest(struct netfs_read_subrequest *subreq) > +static void netfs_put_subrequest(struct netfs_read_subrequest *subreq, > + bool was_async) > { > if (refcount_dec_and_test(&subreq->usage)) > - __netfs_put_subrequest(subreq); > + __netfs_put_subrequest(subreq, was_async); > } > > static struct netfs_read_request *netfs_alloc_read_request( > @@ -67,7 +68,8 @@ static void netfs_get_read_request(struct netfs_read_request *rreq) > refcount_inc(&rreq->usage); > } > > -static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq) > +static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq, > + bool was_async) > { > struct netfs_read_subrequest *subreq; > > @@ -75,7 +77,7 @@ static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq) > subreq = list_first_entry(&rreq->subrequests, > struct netfs_read_subrequest, rreq_link); > list_del(&subreq->rreq_link); > - netfs_put_subrequest(subreq); > + netfs_put_subrequest(subreq, was_async); > } > } > > @@ -83,7 +85,7 @@ static void netfs_free_read_request(struct work_struct *work) > { > struct netfs_read_request *rreq = > container_of(work, struct netfs_read_request, work); > - netfs_rreq_clear_subreqs(rreq); > + netfs_rreq_clear_subreqs(rreq, false); > if (rreq->netfs_priv) > rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv); > trace_netfs_rreq(rreq, netfs_rreq_trace_free); > @@ -93,10 +95,10 @@ static void netfs_free_read_request(struct work_struct *work) > netfs_stat_d(&netfs_n_rh_rreq); > } > > -static void netfs_put_read_request(struct netfs_read_request *rreq) > +static void netfs_put_read_request(struct netfs_read_request *rreq, bool was_async) > { > if (refcount_dec_and_test(&rreq->usage)) { > - if (in_softirq()) { > + if (was_async) { > rreq->work.func = netfs_free_read_request; > if (!queue_work(system_unbound_wq, &rreq->work)) > BUG(); > @@ -131,12 +133,15 @@ static void netfs_get_read_subrequest(struct netfs_read_subrequest *subreq) > refcount_inc(&subreq->usage); > } > > -static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq) > +static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq, > + bool was_async) > { > + struct netfs_read_request *rreq = subreq->rreq; > + > trace_netfs_sreq(subreq, netfs_sreq_trace_free); > - netfs_put_read_request(subreq->rreq); > kfree(subreq); > netfs_stat_d(&netfs_n_rh_sreq); > + netfs_put_read_request(rreq, was_async); > } > > /* > @@ -152,11 +157,12 @@ static void netfs_clear_unread(struct netfs_read_subrequest *subreq) > iov_iter_zero(iov_iter_count(&iter), &iter); > } > > -static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error) > +static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error, > + bool was_async) > { > struct netfs_read_subrequest *subreq = priv; > > - netfs_subreq_terminated(subreq, transferred_or_error); > + netfs_subreq_terminated(subreq, transferred_or_error, was_async); > } > > /* > @@ -186,7 +192,7 @@ static void netfs_fill_with_zeroes(struct netfs_read_request *rreq, > { > netfs_stat(&netfs_n_rh_zero); > __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags); > - netfs_subreq_terminated(subreq, 0); > + netfs_subreq_terminated(subreq, 0, false); > } > > /* > @@ -215,11 +221,11 @@ static void netfs_read_from_server(struct netfs_read_request *rreq, > /* > * Release those waiting. > */ > -static void netfs_rreq_completed(struct netfs_read_request *rreq) > +static void netfs_rreq_completed(struct netfs_read_request *rreq, bool was_async) > { > trace_netfs_rreq(rreq, netfs_rreq_trace_done); > - netfs_rreq_clear_subreqs(rreq); > - netfs_put_read_request(rreq); > + netfs_rreq_clear_subreqs(rreq, was_async); > + netfs_put_read_request(rreq, was_async); > } > > /* > @@ -228,7 +234,8 @@ static void netfs_rreq_completed(struct netfs_read_request *rreq) > * > * May be called in softirq mode and we inherit a ref from the caller. > */ > -static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq) > +static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq, > + bool was_async) > { > struct netfs_read_subrequest *subreq; > struct pagevec pvec; > @@ -258,10 +265,11 @@ static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq) > } > > rcu_read_unlock(); > - netfs_rreq_completed(rreq); > + netfs_rreq_completed(rreq, was_async); > } > > -static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error) > +static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error, > + bool was_async) > { > struct netfs_read_subrequest *subreq = priv; > struct netfs_read_request *rreq = subreq->rreq; > @@ -278,9 +286,9 @@ static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error) > > /* If we decrement nr_wr_ops to 0, the ref belongs to us. */ > if (atomic_dec_and_test(&rreq->nr_wr_ops)) > - netfs_rreq_unmark_after_write(rreq); > + netfs_rreq_unmark_after_write(rreq, was_async); > > - netfs_put_subrequest(subreq); > + netfs_put_subrequest(subreq, was_async); > } > > /* > @@ -304,7 +312,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq) > list_for_each_entry_safe(subreq, p, &rreq->subrequests, rreq_link) { > if (!test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags)) { > list_del_init(&subreq->rreq_link); > - netfs_put_subrequest(subreq); > + netfs_put_subrequest(subreq, false); > } > } > > @@ -324,7 +332,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq) > subreq->len += next->len; > subreq->len = round_up(subreq->len, PAGE_SIZE); > list_del_init(&next->rreq_link); > - netfs_put_subrequest(next); > + netfs_put_subrequest(next, false); > } > > iov_iter_xarray(&iter, WRITE, &rreq->mapping->i_pages, > @@ -340,7 +348,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq) > > /* If we decrement nr_wr_ops to 0, the usage ref belongs to us. */ > if (atomic_dec_and_test(&rreq->nr_wr_ops)) > - netfs_rreq_unmark_after_write(rreq); > + netfs_rreq_unmark_after_write(rreq, false); > } > > static void netfs_rreq_write_to_cache_work(struct work_struct *work) > @@ -351,9 +359,10 @@ static void netfs_rreq_write_to_cache_work(struct work_struct *work) > netfs_rreq_do_write_to_cache(rreq); > } > > -static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq) > +static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq, > + bool was_async) > { > - if (in_softirq()) { > + if (was_async) { > rreq->work.func = netfs_rreq_write_to_cache_work; > if (!queue_work(system_unbound_wq, &rreq->work)) > BUG(); > @@ -479,7 +488,7 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq) > { > struct netfs_read_subrequest *subreq; > > - WARN_ON(in_softirq()); > + WARN_ON(in_interrupt()); > > trace_netfs_rreq(rreq, netfs_rreq_trace_resubmit); > > @@ -538,7 +547,7 @@ static void netfs_rreq_is_still_valid(struct netfs_read_request *rreq) > * Note that we could be in an ordinary kernel thread, on a workqueue or in > * softirq context at this point. We inherit a ref from the caller. > */ > -static void netfs_rreq_assess(struct netfs_read_request *rreq) > +static void netfs_rreq_assess(struct netfs_read_request *rreq, bool was_async) > { > trace_netfs_rreq(rreq, netfs_rreq_trace_assess); > > @@ -558,30 +567,31 @@ static void netfs_rreq_assess(struct netfs_read_request *rreq) > wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS); > > if (test_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags)) > - return netfs_rreq_write_to_cache(rreq); > + return netfs_rreq_write_to_cache(rreq, was_async); > > - netfs_rreq_completed(rreq); > + netfs_rreq_completed(rreq, was_async); > } > > static void netfs_rreq_work(struct work_struct *work) > { > struct netfs_read_request *rreq = > container_of(work, struct netfs_read_request, work); > - netfs_rreq_assess(rreq); > + netfs_rreq_assess(rreq, false); > } > > /* > * Handle the completion of all outstanding I/O operations on a read request. > * We inherit a ref from the caller. > */ > -static void netfs_rreq_terminated(struct netfs_read_request *rreq) > +static void netfs_rreq_terminated(struct netfs_read_request *rreq, > + bool was_async) > { > if (test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags) && > - in_softirq()) { > + was_async) { > if (!queue_work(system_unbound_wq, &rreq->work)) > BUG(); > } else { > - netfs_rreq_assess(rreq); > + netfs_rreq_assess(rreq, was_async); > } > } > > @@ -589,6 +599,7 @@ static void netfs_rreq_terminated(struct netfs_read_request *rreq) > * netfs_subreq_terminated - Note the termination of an I/O operation. > * @subreq: The I/O request that has terminated. > * @transferred_or_error: The amount of data transferred or an error code. > + * @was_async: The termination was asynchronous > * > * This tells the read helper that a contributory I/O operation has terminated, > * one way or another, and that it should integrate the results. > @@ -599,11 +610,12 @@ static void netfs_rreq_terminated(struct netfs_read_request *rreq) > * error code. The helper will look after reissuing I/O operations as > * appropriate and writing downloaded data to the cache. > * > - * This may be called from a softirq handler, so we want to avoid taking the > - * spinlock if we can. > + * If @was_async is true, the caller might be running in softirq or interrupt > + * context and we can't sleep. > */ > void netfs_subreq_terminated(struct netfs_read_subrequest *subreq, > - ssize_t transferred_or_error) > + ssize_t transferred_or_error, > + bool was_async) > { > struct netfs_read_request *rreq = subreq->rreq; > int u; > @@ -647,11 +659,11 @@ void netfs_subreq_terminated(struct netfs_read_subrequest *subreq, > /* If we decrement nr_rd_ops to 0, the ref belongs to us. */ > u = atomic_dec_return(&rreq->nr_rd_ops); > if (u == 0) > - netfs_rreq_terminated(rreq); > + netfs_rreq_terminated(rreq, was_async); > else if (u == 1) > wake_up_var(&rreq->nr_rd_ops); > > - netfs_put_subrequest(subreq); > + netfs_put_subrequest(subreq, was_async); > return; > > incomplete: > @@ -796,7 +808,7 @@ static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq, > > subreq_failed: > rreq->error = subreq->error; > - netfs_put_subrequest(subreq); > + netfs_put_subrequest(subreq, false); > return false; > } > > @@ -901,7 +913,7 @@ void netfs_readahead(struct readahead_control *ractl, > } while (rreq->submitted < rreq->len); > > if (rreq->submitted == 0) { > - netfs_put_read_request(rreq); > + netfs_put_read_request(rreq, false); > return; > } > > @@ -913,11 +925,11 @@ void netfs_readahead(struct readahead_control *ractl, > > /* If we decrement nr_rd_ops to 0, the ref belongs to us. */ > if (atomic_dec_and_test(&rreq->nr_rd_ops)) > - netfs_rreq_assess(rreq); > + netfs_rreq_assess(rreq, false); > return; > > cleanup_free: > - netfs_put_read_request(rreq); > + netfs_put_read_request(rreq, false); > return; > cleanup: > if (netfs_priv) > @@ -991,14 +1003,14 @@ int netfs_readpage(struct file *file, > */ > do { > wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1); > - netfs_rreq_assess(rreq); > + netfs_rreq_assess(rreq, false); > } while (test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags)); > > ret = rreq->error; > if (ret == 0 && rreq->submitted < rreq->len) > ret = -EIO; > out: > - netfs_put_read_request(rreq); > + netfs_put_read_request(rreq, false); > return ret; > } > EXPORT_SYMBOL(netfs_readpage); > @@ -1136,7 +1148,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping, > */ > for (;;) { > wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1); > - netfs_rreq_assess(rreq); > + netfs_rreq_assess(rreq, false); > if (!test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags)) > break; > cond_resched(); > @@ -1145,7 +1157,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping, > ret = rreq->error; > if (ret == 0 && rreq->submitted < rreq->len) > ret = -EIO; > - netfs_put_read_request(rreq); > + netfs_put_read_request(rreq, false); > if (ret < 0) > goto error; > > diff --git a/include/linux/netfs.h b/include/linux/netfs.h > index b2589b39feb8..c22b64db237d 100644 > --- a/include/linux/netfs.h > +++ b/include/linux/netfs.h > @@ -60,7 +60,8 @@ enum netfs_read_source { > NETFS_INVALID_READ, > } __mode(byte); > > -typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error); > +typedef void (*netfs_io_terminated_t)(void *priv, ssize_t transferred_or_error, > + bool was_async); > > /* > * Resources required to do operations on a cache. > @@ -189,7 +190,7 @@ extern int netfs_write_begin(struct file *, struct address_space *, > const struct netfs_read_request_ops *, > void *); > > -extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t); > +extern void netfs_subreq_terminated(struct netfs_read_subrequest *, ssize_t, bool); > extern void netfs_stats_show(struct seq_file *); > > #endif /* _LINUX_NETFS_H */ > > Looks good in testing. Tested-by: Marc Dionne <marc.dionne@auristor.com>
On 2021-02-18 14:02:36 [+0000], David Howells wrote: > How about the attached instead? Thank you for that flag. > David Sebastian
diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c index 9191a3617d91..db582008b4bd 100644 --- a/fs/netfs/read_helper.c +++ b/fs/netfs/read_helper.c @@ -96,7 +96,7 @@ static void netfs_free_read_request(struct work_struct *work) static void netfs_put_read_request(struct netfs_read_request *rreq) { if (refcount_dec_and_test(&rreq->usage)) { - if (in_softirq()) { + if (in_interrupt()) { rreq->work.func = netfs_free_read_request; if (!queue_work(system_unbound_wq, &rreq->work)) BUG(); @@ -353,7 +353,7 @@ static void netfs_rreq_write_to_cache_work(struct work_struct *work) static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq) { - if (in_softirq()) { + if (in_interrupt()) { rreq->work.func = netfs_rreq_write_to_cache_work; if (!queue_work(system_unbound_wq, &rreq->work)) BUG(); @@ -479,7 +479,7 @@ static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq) { struct netfs_read_subrequest *subreq; - WARN_ON(in_softirq()); + WARN_ON(in_interrupt()); trace_netfs_rreq(rreq, netfs_rreq_trace_resubmit); @@ -577,7 +577,7 @@ static void netfs_rreq_work(struct work_struct *work) static void netfs_rreq_terminated(struct netfs_read_request *rreq) { if (test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags) && - in_softirq()) { + in_interrupt()) { if (!queue_work(system_unbound_wq, &rreq->work)) BUG(); } else {
The in_softirq() in netfs_rreq_terminated() works fine for the cache being on a normal disk, as the completion handlers may get called in softirq context, but for an NVMe drive, the completion handler may get called in IRQ context. Fix to use in_interrupt() instead of in_softirq() throughout the read helpers, particularly when deciding whether to punt code that might sleep off to a worker thread. The symptom involves warnings like the following appearing and the kernel hanging: WARNING: CPU: 0 PID: 0 at kernel/softirq.c:175 __local_bh_enable_ip+0x35/0x50 ... RIP: 0010:__local_bh_enable_ip+0x35/0x50 ... Call Trace: <IRQ> rxrpc_kernel_begin_call+0x7d/0x1b0 [rxrpc] ? afs_rx_new_call+0x40/0x40 [kafs] ? afs_alloc_call+0x28/0x120 [kafs] afs_make_call+0x120/0x510 [kafs] ? afs_rx_new_call+0x40/0x40 [kafs] ? afs_alloc_flat_call+0xba/0x100 [kafs] ? __kmalloc+0x167/0x2f0 ? afs_alloc_flat_call+0x9b/0x100 [kafs] afs_wait_for_operation+0x2d/0x200 [kafs] afs_do_sync_operation+0x16/0x20 [kafs] afs_req_issue_op+0x8c/0xb0 [kafs] netfs_rreq_assess+0x125/0x7d0 [netfs] ? cachefiles_end_operation+0x40/0x40 [cachefiles] netfs_subreq_terminated+0x117/0x220 [netfs] cachefiles_read_complete+0x21/0x60 [cachefiles] iomap_dio_bio_end_io+0xdd/0x110 blk_update_request+0x20a/0x380 blk_mq_end_request+0x1c/0x120 nvme_process_cq+0x159/0x1f0 [nvme] nvme_irq+0x10/0x20 [nvme] __handle_irq_event_percpu+0x37/0x150 handle_irq_event+0x49/0xb0 handle_edge_irq+0x7c/0x200 asm_call_irq_on_stack+0xf/0x20 </IRQ> common_interrupt+0xad/0x120 asm_common_interrupt+0x1e/0x40 ... Reported-by: Marc Dionne <marc.dionne@auristor.com> Signed-off-by: David Howells <dhowells@redhat.com> cc: Matthew Wilcox <willy@infradead.org> cc: linux-mm@kvack.org cc: linux-cachefs@redhat.com cc: linux-afs@lists.infradead.org cc: linux-nfs@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-fsdevel@vger.kernel.org --- read_helper.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)