[v2] libceph: increase the max extents check for sparse read

From: Xiubo Li <xiubli@redhat.com>

There is no any limit for the extent array size and it's possible
that we will hit 4096 limit just after a lot of random writes to
a file and then read with a large size. In this case the messager
will fail by reseting the connection and keeps resending the inflight
IOs infinitely.

Just increase the limit to a larger number and then warn it to
let user know that allocating memory could fail with this.

URL: https://tracker.ceph.com/issues/62081
Signed-off-by: Xiubo Li <xiubli@redhat.com>
---

V2:
- Increase the MAX_EXTENTS instead of removing it.
- Do not return an errno when hit the limit.


 net/ceph/osd_client.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

On Mon, Nov 6, 2023 at 2:05 AM <xiubli@redhat.com> wrote:
>
> From: Xiubo Li <xiubli@redhat.com>
>
> There is no any limit for the extent array size and it's possible
> that we will hit 4096 limit just after a lot of random writes to
> a file and then read with a large size. In this case the messager
> will fail by reseting the connection and keeps resending the inflight
> IOs infinitely.
>
> Just increase the limit to a larger number and then warn it to
> let user know that allocating memory could fail with this.
>
> URL: https://tracker.ceph.com/issues/62081
> Signed-off-by: Xiubo Li <xiubli@redhat.com>
> ---
>
> V2:
> - Increase the MAX_EXTENTS instead of removing it.
> - Do not return an errno when hit the limit.
>
>
>  net/ceph/osd_client.c | 15 +++++++--------
>  1 file changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
> index c03d48bd3aff..050dc39065fb 100644
> --- a/net/ceph/osd_client.c
> +++ b/net/ceph/osd_client.c
> @@ -5850,7 +5850,7 @@ static inline void convert_extent_map(struct ceph_sparse_read *sr)
>  }
>  #endif
>
> -#define MAX_EXTENTS 4096
> +#define MAX_EXTENTS (16*1024*1024)

I don't think this is a sensible limit -- see my other reply.

Thanks,

                Ilya

On Mon, Nov 6, 2023 at 1:20 PM Xiubo Li <xiubli@redhat.com> wrote:
>
>
> On 11/6/23 19:46, Ilya Dryomov wrote:
> > On Mon, Nov 6, 2023 at 2:05 AM <xiubli@redhat.com> wrote:
> >> From: Xiubo Li <xiubli@redhat.com>
> >>
> >> There is no any limit for the extent array size and it's possible
> >> that we will hit 4096 limit just after a lot of random writes to
> >> a file and then read with a large size. In this case the messager
> >> will fail by reseting the connection and keeps resending the inflight
> >> IOs infinitely.
> >>
> >> Just increase the limit to a larger number and then warn it to
> >> let user know that allocating memory could fail with this.
> >>
> >> URL: https://tracker.ceph.com/issues/62081
> >> Signed-off-by: Xiubo Li <xiubli@redhat.com>
> >> ---
> >>
> >> V2:
> >> - Increase the MAX_EXTENTS instead of removing it.
> >> - Do not return an errno when hit the limit.
> >>
> >>
> >>   net/ceph/osd_client.c | 15 +++++++--------
> >>   1 file changed, 7 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
> >> index c03d48bd3aff..050dc39065fb 100644
> >> --- a/net/ceph/osd_client.c
> >> +++ b/net/ceph/osd_client.c
> >> @@ -5850,7 +5850,7 @@ static inline void convert_extent_map(struct ceph_sparse_read *sr)
> >>   }
> >>   #endif
> >>
> >> -#define MAX_EXTENTS 4096
> >> +#define MAX_EXTENTS (16*1024*1024)
> > I don't think this is a sensible limit -- see my other reply.
>
> Ilya,
>
> As I mentioned in that thread, the sparse read could be enabled in
> non-fscrypt case. If so the "64M (CEPH_MSG_MAX_DATA_LEN) / 4K = 16384"
> still won't be enough.

I have just replied in the other thread.  Let's continue this
discussion there ;)

Thanks,

                Ilya