Messages in this thread | | | From | "Fabio M. De Francesco" <> | Subject | Re: [PATCH v3 41/55] iscsi: Assume "sendpage" is okay in iscsi_tcp_segment_map() | Date | Mon, 24 Apr 2023 19:19:04 +0200 |
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On venerdì 31 marzo 2023 18:09:00 CEST David Howells wrote: > As iscsi is now using sendmsg() with MSG_SPLICE_PAGES rather than sendpage, > assume that sendpage_ok() will return true in iscsi_tcp_segment_map() and > leave it to TCP to copy the data if not. > > Signed-off-by: David Howells <dhowells@redhat.com> > cc: "Martin K. Petersen" <martin.petersen@oracle.com> > cc: "David S. Miller" <davem@davemloft.net> > cc: Eric Dumazet <edumazet@google.com> > cc: Jakub Kicinski <kuba@kernel.org> > cc: Paolo Abeni <pabeni@redhat.com> > cc: Jens Axboe <axboe@kernel.dk> > cc: Matthew Wilcox <willy@infradead.org> > cc: linux-scsi@vger.kernel.org > cc: target-devel@vger.kernel.org > cc: netdev@vger.kernel.org > --- > drivers/scsi/libiscsi_tcp.c | 13 +++---------- > 1 file changed, 3 insertions(+), 10 deletions(-) > > diff --git a/drivers/scsi/libiscsi_tcp.c b/drivers/scsi/libiscsi_tcp.c > index c182aa83f2c9..07ba0d864820 100644 > --- a/drivers/scsi/libiscsi_tcp.c > +++ b/drivers/scsi/libiscsi_tcp.c > @@ -128,18 +128,11 @@ static void iscsi_tcp_segment_map(struct iscsi_segment > *segment, int recv) * coalescing neighboring slab objects into a single frag > which > * triggers one of hardened usercopy checks. > */ > - if (!recv && sendpage_ok(sg_page(sg))) > + if (!recv) > return; > > - if (recv) { > - segment->atomic_mapped = true; > - segment->sg_mapped = kmap_atomic(sg_page(sg)); > - } else { > - segment->atomic_mapped = false; > - /* the xmit path can sleep with the page mapped so use kmap */ > - segment->sg_mapped = kmap(sg_page(sg)); > - } > - > + segment->atomic_mapped = true; > + segment->sg_mapped = kmap_atomic(sg_page(sg));
As you probably know, kmap_atomic() is deprecated.
I must admit that I'm not an expert of this code, however, it looks like the mapping has no need to rely on the side effects of kmap_atomic() (i.e., pagefault_disable() and preempt_disable() - but I'm not entirely sure about the possibility that preemption should be explicitly disabled along with the replacement with kmap_local_page()).
Last year I've been working on several conversions from kmap{,_atomic}() to kmap_local_page(), however I'm still not sure to understand what's happening here...
Am I missing any important details? Can you please explain why we still need that kmap_atomic() instead of kmap_local_page()?
Thanks in advance,
Fabio
> segment->data = segment->sg_mapped + sg->offset + segment- >sg_offset; > }
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