[PATCH] ceph: decoding error in ceph_update_snap_realm should return -EIO

[PATCH] ceph: decoding error in ceph_update_snap_realm should return -EIO

[Jeff Layton]

Currently ceph_update_snap_realm returns -EINVAL when it hits a decoding
error, which is the wrong error code. -EINVAL implies that the user gave
us a bogus argument to a syscall or something similar. -EIO is more
descriptive when we hit a decoding error.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/ceph/snap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index d07c1c6ac8fb..f8cac2abab3f 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -807,7 +807,7 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
 	return 0;
 
 bad:
-	err = -EINVAL;
+	err = -EIO;
 fail:
 	if (realm && !IS_ERR(realm))
 		ceph_put_snap_realm(mdsc, realm);
-- 
2.31.1

Re: [PATCH] ceph: decoding error in ceph_update_snap_realm should return -EIO

[Ilya Dryomov]

On Thu, Jun 3, 2021 at 3:39 PM Jeff Layton <jlayton@kernel.org> wrote:
>
> Currently ceph_update_snap_realm returns -EINVAL when it hits a decoding
> error, which is the wrong error code. -EINVAL implies that the user gave
> us a bogus argument to a syscall or something similar. -EIO is more
> descriptive when we hit a decoding error.
>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  fs/ceph/snap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
> index d07c1c6ac8fb..f8cac2abab3f 100644
> --- a/fs/ceph/snap.c
> +++ b/fs/ceph/snap.c
> @@ -807,7 +807,7 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
>         return 0;
>
>  bad:
> -       err = -EINVAL;
> +       err = -EIO;
>  fail:
>         if (realm && !IS_ERR(realm))
>                 ceph_put_snap_realm(mdsc, realm);

Hi Jeff,

Is this error code propagated anywhere important?

The vast majority of functions that have something to do with decoding
use EINVAL as a default (usually out-of-bounds) error.  I agree that it
is totally ambiguous, but EIO doesn't seem to be any better to me.  If
there is a desire to separate these errors, I think we need to pick
something much more distinctive.

Thanks,

                Ilya

Re: [PATCH] ceph: decoding error in ceph_update_snap_realm should return -EIO

[Jeff Layton]

On Thu, 2021-06-03 at 15:57 +0200, Ilya Dryomov wrote:
> On Thu, Jun 3, 2021 at 3:39 PM Jeff Layton <jlayton@kernel.org> wrote:
> > 
> > Currently ceph_update_snap_realm returns -EINVAL when it hits a decoding
> > error, which is the wrong error code. -EINVAL implies that the user gave
> > us a bogus argument to a syscall or something similar. -EIO is more
> > descriptive when we hit a decoding error.
> > 
> > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > ---
> >  fs/ceph/snap.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
> > index d07c1c6ac8fb..f8cac2abab3f 100644
> > --- a/fs/ceph/snap.c
> > +++ b/fs/ceph/snap.c
> > @@ -807,7 +807,7 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
> >         return 0;
> > 
> >  bad:
> > -       err = -EINVAL;
> > +       err = -EIO;
> >  fail:
> >         if (realm && !IS_ERR(realm))
> >                 ceph_put_snap_realm(mdsc, realm);
> 
> Hi Jeff,
> 
> Is this error code propagated anywhere important?
> 
> The vast majority of functions that have something to do with decoding
> use EINVAL as a default (usually out-of-bounds) error.  I agree that it
> is totally ambiguous, but EIO doesn't seem to be any better to me.  If
> there is a desire to separate these errors, I think we need to pick
> something much more distinctive.
> 

When I see EINVAL, I automatically wonder what bogus argument I passed
in somewhere, so I find that particularly deceptive here where the bug
is either from the MDS or we had some sort of low-level socket handling
problem.

OTOH, you have a good point. The callers universally ignore the error
code from this function. Perhaps we ought to just log a pr_warn message
or something if the decoding fails here instead?
-- 
Jeff Layton <jlayton@kernel.org>

Re: [PATCH] ceph: decoding error in ceph_update_snap_realm should return -EIO

[Ilya Dryomov]

On Thu, Jun 3, 2021 at 4:02 PM Jeff Layton <jlayton@kernel.org> wrote:
>
> On Thu, 2021-06-03 at 15:57 +0200, Ilya Dryomov wrote:
> > On Thu, Jun 3, 2021 at 3:39 PM Jeff Layton <jlayton@kernel.org> wrote:
> > >
> > > Currently ceph_update_snap_realm returns -EINVAL when it hits a decoding
> > > error, which is the wrong error code. -EINVAL implies that the user gave
> > > us a bogus argument to a syscall or something similar. -EIO is more
> > > descriptive when we hit a decoding error.
> > >
> > > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > > ---
> > >  fs/ceph/snap.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
> > > index d07c1c6ac8fb..f8cac2abab3f 100644
> > > --- a/fs/ceph/snap.c
> > > +++ b/fs/ceph/snap.c
> > > @@ -807,7 +807,7 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
> > >         return 0;
> > >
> > >  bad:
> > > -       err = -EINVAL;
> > > +       err = -EIO;
> > >  fail:
> > >         if (realm && !IS_ERR(realm))
> > >                 ceph_put_snap_realm(mdsc, realm);
> >
> > Hi Jeff,
> >
> > Is this error code propagated anywhere important?
> >
> > The vast majority of functions that have something to do with decoding
> > use EINVAL as a default (usually out-of-bounds) error.  I agree that it
> > is totally ambiguous, but EIO doesn't seem to be any better to me.  If
> > there is a desire to separate these errors, I think we need to pick
> > something much more distinctive.
> >
>
> When I see EINVAL, I automatically wonder what bogus argument I passed
> in somewhere, so I find that particularly deceptive here where the bug
> is either from the MDS or we had some sort of low-level socket handling
> problem.
>
> OTOH, you have a good point. The callers universally ignore the error
> code from this function. Perhaps we ought to just log a pr_warn message
> or something if the decoding fails here instead?

There already is one:

 793 bad:
 794         err = -EINVAL;
 795 fail:
 796         if (realm && !IS_ERR(realm))
 797                 ceph_put_snap_realm(mdsc, realm);
 798         if (first_realm)
 799                 ceph_put_snap_realm(mdsc, first_realm);
 800         pr_err("update_snap_trace error %d\n", err);
 801         return err;

Or do you mean specifically the "bad" label?

Thanks,

                Ilya

Re: [PATCH] ceph: decoding error in ceph_update_snap_realm should return -EIO

[Jeff Layton]

On Thu, 2021-06-03 at 16:33 +0200, Ilya Dryomov wrote:
> On Thu, Jun 3, 2021 at 4:02 PM Jeff Layton <jlayton@kernel.org> wrote:
> > 
> > On Thu, 2021-06-03 at 15:57 +0200, Ilya Dryomov wrote:
> > > On Thu, Jun 3, 2021 at 3:39 PM Jeff Layton <jlayton@kernel.org> wrote:
> > > > 
> > > > Currently ceph_update_snap_realm returns -EINVAL when it hits a decoding
> > > > error, which is the wrong error code. -EINVAL implies that the user gave
> > > > us a bogus argument to a syscall or something similar. -EIO is more
> > > > descriptive when we hit a decoding error.
> > > > 
> > > > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > > > ---
> > > >  fs/ceph/snap.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
> > > > index d07c1c6ac8fb..f8cac2abab3f 100644
> > > > --- a/fs/ceph/snap.c
> > > > +++ b/fs/ceph/snap.c
> > > > @@ -807,7 +807,7 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
> > > >         return 0;
> > > > 
> > > >  bad:
> > > > -       err = -EINVAL;
> > > > +       err = -EIO;
> > > >  fail:
> > > >         if (realm && !IS_ERR(realm))
> > > >                 ceph_put_snap_realm(mdsc, realm);
> > > 
> > > Hi Jeff,
> > > 
> > > Is this error code propagated anywhere important?
> > > 
> > > The vast majority of functions that have something to do with decoding
> > > use EINVAL as a default (usually out-of-bounds) error.  I agree that it
> > > is totally ambiguous, but EIO doesn't seem to be any better to me.  If
> > > there is a desire to separate these errors, I think we need to pick
> > > something much more distinctive.
> > > 
> > 
> > When I see EINVAL, I automatically wonder what bogus argument I passed
> > in somewhere, so I find that particularly deceptive here where the bug
> > is either from the MDS or we had some sort of low-level socket handling
> > problem.
> > 
> > OTOH, you have a good point. The callers universally ignore the error
> > code from this function. Perhaps we ought to just log a pr_warn message
> > or something if the decoding fails here instead?
> 
> There already is one:
> 
>  793 bad:
>  794         err = -EINVAL;
>  795 fail:
>  796         if (realm && !IS_ERR(realm))
>  797                 ceph_put_snap_realm(mdsc, realm);
>  798         if (first_realm)
>  799                 ceph_put_snap_realm(mdsc, first_realm);
>  800         pr_err("update_snap_trace error %d\n", err);
>  801         return err;
> 
> Or do you mean specifically the "bad" label?
> 

Well, if we have a distinctive error code there, then we won't need a
separate pr_err message or anything. I still think that -EINVAL is not
descriptive of the issue though. I suppose if -EIO is too vague, we
could use something like -EILSEQ ?

-- 
Jeff Layton <jlayton@kernel.org>

Re: [PATCH] ceph: decoding error in ceph_update_snap_realm should return -EIO

[Ilya Dryomov]

On Thu, Jun 3, 2021 at 4:42 PM Jeff Layton <jlayton@kernel.org> wrote:
>
> On Thu, 2021-06-03 at 16:33 +0200, Ilya Dryomov wrote:
> > On Thu, Jun 3, 2021 at 4:02 PM Jeff Layton <jlayton@kernel.org> wrote:
> > >
> > > On Thu, 2021-06-03 at 15:57 +0200, Ilya Dryomov wrote:
> > > > On Thu, Jun 3, 2021 at 3:39 PM Jeff Layton <jlayton@kernel.org> wrote:
> > > > >
> > > > > Currently ceph_update_snap_realm returns -EINVAL when it hits a decoding
> > > > > error, which is the wrong error code. -EINVAL implies that the user gave
> > > > > us a bogus argument to a syscall or something similar. -EIO is more
> > > > > descriptive when we hit a decoding error.
> > > > >
> > > > > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > > > > ---
> > > > >  fs/ceph/snap.c | 2 +-
> > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
> > > > > index d07c1c6ac8fb..f8cac2abab3f 100644
> > > > > --- a/fs/ceph/snap.c
> > > > > +++ b/fs/ceph/snap.c
> > > > > @@ -807,7 +807,7 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
> > > > >         return 0;
> > > > >
> > > > >  bad:
> > > > > -       err = -EINVAL;
> > > > > +       err = -EIO;
> > > > >  fail:
> > > > >         if (realm && !IS_ERR(realm))
> > > > >                 ceph_put_snap_realm(mdsc, realm);
> > > >
> > > > Hi Jeff,
> > > >
> > > > Is this error code propagated anywhere important?
> > > >
> > > > The vast majority of functions that have something to do with decoding
> > > > use EINVAL as a default (usually out-of-bounds) error.  I agree that it
> > > > is totally ambiguous, but EIO doesn't seem to be any better to me.  If
> > > > there is a desire to separate these errors, I think we need to pick
> > > > something much more distinctive.
> > > >
> > >
> > > When I see EINVAL, I automatically wonder what bogus argument I passed
> > > in somewhere, so I find that particularly deceptive here where the bug
> > > is either from the MDS or we had some sort of low-level socket handling
> > > problem.
> > >
> > > OTOH, you have a good point. The callers universally ignore the error
> > > code from this function. Perhaps we ought to just log a pr_warn message
> > > or something if the decoding fails here instead?
> >
> > There already is one:
> >
> >  793 bad:
> >  794         err = -EINVAL;
> >  795 fail:
> >  796         if (realm && !IS_ERR(realm))
> >  797                 ceph_put_snap_realm(mdsc, realm);
> >  798         if (first_realm)
> >  799                 ceph_put_snap_realm(mdsc, first_realm);
> >  800         pr_err("update_snap_trace error %d\n", err);
> >  801         return err;
> >
> > Or do you mean specifically the "bad" label?
> >
>
> Well, if we have a distinctive error code there, then we won't need a
> separate pr_err message or anything. I still think that -EINVAL is not
> descriptive of the issue though. I suppose if -EIO is too vague, we
> could use something like -EILSEQ ?

In a sense it is an invalid argument because the buffer passed to the
decoding function is too short.  This is what would lead to EINVAL here
and in many other decoding-related functions.

EINVAL is the standard error code for "buffer/message too short" in
many other APIs.  EILSEQ is certainly more distinctive, but I'm not
sure it is the "right" error code for this kind of error.

Thanks,

                Ilya

Re: [PATCH] ceph: decoding error in ceph_update_snap_realm should return -EIO

[Jeff Layton]

On Thu, 2021-06-03 at 17:19 +0200, Ilya Dryomov wrote:
> On Thu, Jun 3, 2021 at 4:42 PM Jeff Layton <jlayton@kernel.org> wrote:
> > 
> > On Thu, 2021-06-03 at 16:33 +0200, Ilya Dryomov wrote:
> > > On Thu, Jun 3, 2021 at 4:02 PM Jeff Layton <jlayton@kernel.org> wrote:
> > > > 
> > > > On Thu, 2021-06-03 at 15:57 +0200, Ilya Dryomov wrote:
> > > > > On Thu, Jun 3, 2021 at 3:39 PM Jeff Layton <jlayton@kernel.org> wrote:
> > > > > > 
> > > > > > Currently ceph_update_snap_realm returns -EINVAL when it hits a decoding
> > > > > > error, which is the wrong error code. -EINVAL implies that the user gave
> > > > > > us a bogus argument to a syscall or something similar. -EIO is more
> > > > > > descriptive when we hit a decoding error.
> > > > > > 
> > > > > > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > > > > > ---
> > > > > >  fs/ceph/snap.c | 2 +-
> > > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > > 
> > > > > > diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
> > > > > > index d07c1c6ac8fb..f8cac2abab3f 100644
> > > > > > --- a/fs/ceph/snap.c
> > > > > > +++ b/fs/ceph/snap.c
> > > > > > @@ -807,7 +807,7 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
> > > > > >         return 0;
> > > > > > 
> > > > > >  bad:
> > > > > > -       err = -EINVAL;
> > > > > > +       err = -EIO;
> > > > > >  fail:
> > > > > >         if (realm && !IS_ERR(realm))
> > > > > >                 ceph_put_snap_realm(mdsc, realm);
> > > > > 
> > > > > Hi Jeff,
> > > > > 
> > > > > Is this error code propagated anywhere important?
> > > > > 
> > > > > The vast majority of functions that have something to do with decoding
> > > > > use EINVAL as a default (usually out-of-bounds) error.  I agree that it
> > > > > is totally ambiguous, but EIO doesn't seem to be any better to me.  If
> > > > > there is a desire to separate these errors, I think we need to pick
> > > > > something much more distinctive.
> > > > > 
> > > > 
> > > > When I see EINVAL, I automatically wonder what bogus argument I passed
> > > > in somewhere, so I find that particularly deceptive here where the bug
> > > > is either from the MDS or we had some sort of low-level socket handling
> > > > problem.
> > > > 
> > > > OTOH, you have a good point. The callers universally ignore the error
> > > > code from this function. Perhaps we ought to just log a pr_warn message
> > > > or something if the decoding fails here instead?
> > > 
> > > There already is one:
> > > 
> > >  793 bad:
> > >  794         err = -EINVAL;
> > >  795 fail:
> > >  796         if (realm && !IS_ERR(realm))
> > >  797                 ceph_put_snap_realm(mdsc, realm);
> > >  798         if (first_realm)
> > >  799                 ceph_put_snap_realm(mdsc, first_realm);
> > >  800         pr_err("update_snap_trace error %d\n", err);
> > >  801         return err;
> > > 
> > > Or do you mean specifically the "bad" label?
> > > 
> > 
> > Well, if we have a distinctive error code there, then we won't need a
> > separate pr_err message or anything. I still think that -EINVAL is not
> > descriptive of the issue though. I suppose if -EIO is too vague, we
> > could use something like -EILSEQ ?
> 
> In a sense it is an invalid argument because the buffer passed to the
> decoding function is too short.  This is what would lead to EINVAL here
> and in many other decoding-related functions.
> 
> EINVAL is the standard error code for "buffer/message too short" in
> many other APIs.  EILSEQ is certainly more distinctive, but I'm not
> sure it is the "right" error code for this kind of error.
> 

The issue is that almost everywhere else, decoding routines use -EIO for
this. This function is a special snowflake. Why? I don't see any
justification for it.

-- 
Jeff Layton <jlayton@kernel.org>

Re: [PATCH] ceph: decoding error in ceph_update_snap_realm should return -EIO

[Ilya Dryomov]

On Thu, Jun 3, 2021 at 5:20 PM Jeff Layton <jlayton@kernel.org> wrote:
>
> On Thu, 2021-06-03 at 17:19 +0200, Ilya Dryomov wrote:
> > On Thu, Jun 3, 2021 at 4:42 PM Jeff Layton <jlayton@kernel.org> wrote:
> > >
> > > On Thu, 2021-06-03 at 16:33 +0200, Ilya Dryomov wrote:
> > > > On Thu, Jun 3, 2021 at 4:02 PM Jeff Layton <jlayton@kernel.org> wrote:
> > > > >
> > > > > On Thu, 2021-06-03 at 15:57 +0200, Ilya Dryomov wrote:
> > > > > > On Thu, Jun 3, 2021 at 3:39 PM Jeff Layton <jlayton@kernel.org> wrote:
> > > > > > >
> > > > > > > Currently ceph_update_snap_realm returns -EINVAL when it hits a decoding
> > > > > > > error, which is the wrong error code. -EINVAL implies that the user gave
> > > > > > > us a bogus argument to a syscall or something similar. -EIO is more
> > > > > > > descriptive when we hit a decoding error.
> > > > > > >
> > > > > > > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > > > > > > ---
> > > > > > >  fs/ceph/snap.c | 2 +-
> > > > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > > >
> > > > > > > diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
> > > > > > > index d07c1c6ac8fb..f8cac2abab3f 100644
> > > > > > > --- a/fs/ceph/snap.c
> > > > > > > +++ b/fs/ceph/snap.c
> > > > > > > @@ -807,7 +807,7 @@ int ceph_update_snap_trace(struct ceph_mds_client *mdsc,
> > > > > > >         return 0;
> > > > > > >
> > > > > > >  bad:
> > > > > > > -       err = -EINVAL;
> > > > > > > +       err = -EIO;
> > > > > > >  fail:
> > > > > > >         if (realm && !IS_ERR(realm))
> > > > > > >                 ceph_put_snap_realm(mdsc, realm);
> > > > > >
> > > > > > Hi Jeff,
> > > > > >
> > > > > > Is this error code propagated anywhere important?
> > > > > >
> > > > > > The vast majority of functions that have something to do with decoding
> > > > > > use EINVAL as a default (usually out-of-bounds) error.  I agree that it
> > > > > > is totally ambiguous, but EIO doesn't seem to be any better to me.  If
> > > > > > there is a desire to separate these errors, I think we need to pick
> > > > > > something much more distinctive.
> > > > > >
> > > > >
> > > > > When I see EINVAL, I automatically wonder what bogus argument I passed
> > > > > in somewhere, so I find that particularly deceptive here where the bug
> > > > > is either from the MDS or we had some sort of low-level socket handling
> > > > > problem.
> > > > >
> > > > > OTOH, you have a good point. The callers universally ignore the error
> > > > > code from this function. Perhaps we ought to just log a pr_warn message
> > > > > or something if the decoding fails here instead?
> > > >
> > > > There already is one:
> > > >
> > > >  793 bad:
> > > >  794         err = -EINVAL;
> > > >  795 fail:
> > > >  796         if (realm && !IS_ERR(realm))
> > > >  797                 ceph_put_snap_realm(mdsc, realm);
> > > >  798         if (first_realm)
> > > >  799                 ceph_put_snap_realm(mdsc, first_realm);
> > > >  800         pr_err("update_snap_trace error %d\n", err);
> > > >  801         return err;
> > > >
> > > > Or do you mean specifically the "bad" label?
> > > >
> > >
> > > Well, if we have a distinctive error code there, then we won't need a
> > > separate pr_err message or anything. I still think that -EINVAL is not
> > > descriptive of the issue though. I suppose if -EIO is too vague, we
> > > could use something like -EILSEQ ?
> >
> > In a sense it is an invalid argument because the buffer passed to the
> > decoding function is too short.  This is what would lead to EINVAL here
> > and in many other decoding-related functions.
> >
> > EINVAL is the standard error code for "buffer/message too short" in
> > many other APIs.  EILSEQ is certainly more distinctive, but I'm not
> > sure it is the "right" error code for this kind of error.
> >
>
> The issue is that almost everywhere else, decoding routines use -EIO for
> this. This function is a special snowflake. Why? I don't see any
> justification for it.

Ah, indeed I see that there is precedent for using EIO for this in
fs/ceph (although this particular EINVAL goes back to 2009).  I just
wanted to keep things consistent with libceph and rbd where it is
mostly EINVAL.

Sorry for the noise.

Thanks,

                Ilya