| Message ID | 20240710-nfsd-next-v1-1-21fca616ac53@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | nfsd: plug some filecache refcount leaks | expand |
Shouldn't we have fh_put(fhp) before 'retry'? On Wed, Jul 10, 2024 at 9:06 AM Jeff Layton <jlayton@kernel.org> wrote: > > At this point, we have a new nf that we couldn't properly insert into > the hashtable. Just free it before retrying, since it was never hashed. > > Fixes: c6593366c0bf ("nfsd: don't kill nfsd_files because of lease break error") > Signed-off-by: Jeff Layton <jlayton@kernel.org> > --- > fs/nfsd/filecache.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c > index f84913691b78..4fb5e8546831 100644 > --- a/fs/nfsd/filecache.c > +++ b/fs/nfsd/filecache.c > @@ -1038,8 +1038,10 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp, > if (likely(ret == 0)) > goto open_file; > > - if (ret == -EEXIST) > + if (ret == -EEXIST) { > + nfsd_file_free(nf); > goto retry; > + } > trace_nfsd_file_insert_err(rqstp, inode, may_flags, ret); > status = nfserr_jukebox; > goto construction_err; > > -- > 2.45.2 >
On Thu, 2024-07-11 at 13:05 -0400, Youzhong Yang wrote: > Shouldn't we have fh_put(fhp) before 'retry'? > A subtle question, actually... It probably wouldn't hurt to do that, but I don't think it's required. The main reason we call fh_put is to force a second call to nfsd_set_fh_dentry. IOW, we want to redo the lookup by filehandle and find the inode. In the EEXIST case, presumably we have found the inode but we raced with another task in setting an nfsd_file for it in the hash. That's different from the case where the thing was unhashed or we got an EOPENSTALE. So, I think we probably don't require refinding the inode in that case. More pointedly, I'm not sure this particular case is actually possible. The entries are hashed on the inode pointer value, and we're searching and inserting into the hash under the i_lock. Chuck, thoughts? > On Wed, Jul 10, 2024 at 9:06 AM Jeff Layton <jlayton@kernel.org> > wrote: > > > > At this point, we have a new nf that we couldn't properly insert > > into > > the hashtable. Just free it before retrying, since it was never > > hashed. > > > > Fixes: c6593366c0bf ("nfsd: don't kill nfsd_files because of lease > > break error") > > Signed-off-by: Jeff Layton <jlayton@kernel.org> > > --- > > fs/nfsd/filecache.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c > > index f84913691b78..4fb5e8546831 100644 > > --- a/fs/nfsd/filecache.c > > +++ b/fs/nfsd/filecache.c > > @@ -1038,8 +1038,10 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, > > struct svc_fh *fhp, > > if (likely(ret == 0)) > > goto open_file; > > > > - if (ret == -EEXIST) > > + if (ret == -EEXIST) { > > + nfsd_file_free(nf); > > goto retry; > > + } > > trace_nfsd_file_insert_err(rqstp, inode, may_flags, ret); > > status = nfserr_jukebox; > > goto construction_err; > > > > -- > > 2.45.2 > >
> On Jul 11, 2024, at 1:53 PM, Jeff Layton <jlayton@kernel.org> wrote: > > On Thu, 2024-07-11 at 13:05 -0400, Youzhong Yang wrote: >> Shouldn't we have fh_put(fhp) before 'retry'? >> > > A subtle question, actually... > > It probably wouldn't hurt to do that, but I don't think it's required. > > The main reason we call fh_put is to force a second call to > nfsd_set_fh_dentry. IOW, we want to redo the lookup by filehandle and > find the inode. > > In the EEXIST case, presumably we have found the inode but we raced > with another task in setting an nfsd_file for it in the hash. That's > different from the case where the thing was unhashed or we got an > EOPENSTALE. So, I think we probably don't require refinding the inode > in that case. > > More pointedly, I'm not sure this particular case is actually possible. > The entries are hashed on the inode pointer value, and we're searching > and inserting into the hash under the i_lock. > > Chuck, thoughts? Is the question whether we want to dput() the dentry that is attached to the fhp ? fh_verify's API contract says: 310 * Regardless of success or failure of fh_verify(), fh_put() should be 311 * called on @fhp when the caller is finished with the filehandle. It looks like none of nfsd_file_acquire's callers do an fh_put() in their error flows. But maybe I've misunderstood the issue. >> On Wed, Jul 10, 2024 at 9:06 AM Jeff Layton <jlayton@kernel.org> >> wrote: >>> >>> At this point, we have a new nf that we couldn't properly insert >>> into >>> the hashtable. Just free it before retrying, since it was never >>> hashed. >>> >>> Fixes: c6593366c0bf ("nfsd: don't kill nfsd_files because of lease >>> break error") >>> Signed-off-by: Jeff Layton <jlayton@kernel.org> >>> --- >>> fs/nfsd/filecache.c | 4 +++- >>> 1 file changed, 3 insertions(+), 1 deletion(-) >>> >>> diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c >>> index f84913691b78..4fb5e8546831 100644 >>> --- a/fs/nfsd/filecache.c >>> +++ b/fs/nfsd/filecache.c >>> @@ -1038,8 +1038,10 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, >>> struct svc_fh *fhp, >>> if (likely(ret == 0)) >>> goto open_file; >>> >>> - if (ret == -EEXIST) >>> + if (ret == -EEXIST) { >>> + nfsd_file_free(nf); >>> goto retry; >>> + } >>> trace_nfsd_file_insert_err(rqstp, inode, may_flags, ret); >>> status = nfserr_jukebox; >>> goto construction_err; >>> >>> -- >>> 2.45.2 >>> > > -- > Jeff Layton <jlayton@kernel.org> -- Chuck Lever
On Thu, 2024-07-11 at 18:16 +0000, Chuck Lever III wrote: > > > > On Jul 11, 2024, at 1:53 PM, Jeff Layton <jlayton@kernel.org> > > wrote: > > > > On Thu, 2024-07-11 at 13:05 -0400, Youzhong Yang wrote: > > > Shouldn't we have fh_put(fhp) before 'retry'? > > > > > > > A subtle question, actually... > > > > It probably wouldn't hurt to do that, but I don't think it's > > required. > > > > The main reason we call fh_put is to force a second call to > > nfsd_set_fh_dentry. IOW, we want to redo the lookup by filehandle > > and > > find the inode. > > > > In the EEXIST case, presumably we have found the inode but we raced > > with another task in setting an nfsd_file for it in the hash. > > That's > > different from the case where the thing was unhashed or we got an > > EOPENSTALE. So, I think we probably don't require refinding the > > inode > > in that case. > > > > More pointedly, I'm not sure this particular case is actually > > possible. > > The entries are hashed on the inode pointer value, and we're > > searching > > and inserting into the hash under the i_lock. > > > > Chuck, thoughts? > > Is the question whether we want to dput() the dentry that > is attached to the fhp ? fh_verify's API contract says: > > 310 * Regardless of success or failure of fh_verify(), fh_put() > should be > 311 * called on @fhp when the caller is finished with the > filehandle. > > It looks like none of nfsd_file_acquire's callers do an > fh_put() in their error flows. > > But maybe I've misunderstood the issue. > Note that this API is weird and doesn't conform to typical get/put semantics. The fhp is instantiated before nfsd_file_do_acquire is called, and all of the callers that I can see do eventually call fh_put on it. fh_put is idempotent, so there should be no harm in calling it multiple times. My question here though was more about this EEXIST case. Should we even bother checking for that? I don't see how it's possible. > > > > On Wed, Jul 10, 2024 at 9:06 AM Jeff Layton <jlayton@kernel.org> > > > wrote: > > > > > > > > At this point, we have a new nf that we couldn't properly > > > > insert > > > > into > > > > the hashtable. Just free it before retrying, since it was never > > > > hashed. > > > > > > > > Fixes: c6593366c0bf ("nfsd: don't kill nfsd_files because of > > > > lease > > > > break error") > > > > Signed-off-by: Jeff Layton <jlayton@kernel.org> > > > > --- > > > > fs/nfsd/filecache.c | 4 +++- > > > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c > > > > index f84913691b78..4fb5e8546831 100644 > > > > --- a/fs/nfsd/filecache.c > > > > +++ b/fs/nfsd/filecache.c > > > > @@ -1038,8 +1038,10 @@ nfsd_file_do_acquire(struct svc_rqst > > > > *rqstp, > > > > struct svc_fh *fhp, > > > > if (likely(ret == 0)) > > > > goto open_file; > > > > > > > > - if (ret == -EEXIST) > > > > + if (ret == -EEXIST) { > > > > + nfsd_file_free(nf); > > > > goto retry; > > > > + } > > > > trace_nfsd_file_insert_err(rqstp, inode, may_flags, > > > > ret); > > > > status = nfserr_jukebox; > > > > goto construction_err; > > > > > > > > -- > > > > 2.45.2 > > > > > > > > -- > > Jeff Layton <jlayton@kernel.org> > > > -- > Chuck Lever > >
> On Jul 11, 2024, at 2:20 PM, Jeff Layton <jlayton@kernel.org> wrote: > > On Thu, 2024-07-11 at 18:16 +0000, Chuck Lever III wrote: >> >> >>> On Jul 11, 2024, at 1:53 PM, Jeff Layton <jlayton@kernel.org> >>> wrote: >>> >>> On Thu, 2024-07-11 at 13:05 -0400, Youzhong Yang wrote: >>>> Shouldn't we have fh_put(fhp) before 'retry'? >>>> >>> >>> A subtle question, actually... >>> >>> It probably wouldn't hurt to do that, but I don't think it's >>> required. >>> >>> The main reason we call fh_put is to force a second call to >>> nfsd_set_fh_dentry. IOW, we want to redo the lookup by filehandle >>> and >>> find the inode. >>> >>> In the EEXIST case, presumably we have found the inode but we raced >>> with another task in setting an nfsd_file for it in the hash. >>> That's >>> different from the case where the thing was unhashed or we got an >>> EOPENSTALE. So, I think we probably don't require refinding the >>> inode >>> in that case. >>> >>> More pointedly, I'm not sure this particular case is actually >>> possible. >>> The entries are hashed on the inode pointer value, and we're >>> searching >>> and inserting into the hash under the i_lock. >>> >>> Chuck, thoughts? >> >> Is the question whether we want to dput() the dentry that >> is attached to the fhp ? fh_verify's API contract says: >> >> 310 * Regardless of success or failure of fh_verify(), fh_put() >> should be >> 311 * called on @fhp when the caller is finished with the >> filehandle. >> >> It looks like none of nfsd_file_acquire's callers do an >> fh_put() in their error flows. >> >> But maybe I've misunderstood the issue. >> > > Note that this API is weird and doesn't conform to typical get/put > semantics. > > The fhp is instantiated before nfsd_file_do_acquire is called, and all > of the callers that I can see do eventually call fh_put on it. fh_put > is idempotent, so there should be no harm in calling it multiple times. > > My question here though was more about this EEXIST case. Should we even > bother checking for that? I don't see how it's possible. If memory serves, at one point nfsd_file_acquire() used rhtable_insert_yada(), which returns -EEXIST for certain table overflow cases. Possibly with the list version of rhtable, consumers can't get -EEXIST at all. >>>> On Wed, Jul 10, 2024 at 9:06 AM Jeff Layton <jlayton@kernel.org> >>>> wrote: >>>>> >>>>> At this point, we have a new nf that we couldn't properly >>>>> insert >>>>> into >>>>> the hashtable. Just free it before retrying, since it was never >>>>> hashed. >>>>> >>>>> Fixes: c6593366c0bf ("nfsd: don't kill nfsd_files because of >>>>> lease >>>>> break error") >>>>> Signed-off-by: Jeff Layton <jlayton@kernel.org> >>>>> --- >>>>> fs/nfsd/filecache.c | 4 +++- >>>>> 1 file changed, 3 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c >>>>> index f84913691b78..4fb5e8546831 100644 >>>>> --- a/fs/nfsd/filecache.c >>>>> +++ b/fs/nfsd/filecache.c >>>>> @@ -1038,8 +1038,10 @@ nfsd_file_do_acquire(struct svc_rqst >>>>> *rqstp, >>>>> struct svc_fh *fhp, >>>>> if (likely(ret == 0)) >>>>> goto open_file; >>>>> >>>>> - if (ret == -EEXIST) >>>>> + if (ret == -EEXIST) { >>>>> + nfsd_file_free(nf); >>>>> goto retry; >>>>> + } >>>>> trace_nfsd_file_insert_err(rqstp, inode, may_flags, >>>>> ret); >>>>> status = nfserr_jukebox; >>>>> goto construction_err; >>>>> >>>>> -- >>>>> 2.45.2 >>>>> >>> >>> -- >>> Jeff Layton <jlayton@kernel.org> >> >> >> -- >> Chuck Lever >> >> > > -- > Jeff Layton <jlayton@kernel.org> -- Chuck Lever
diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index f84913691b78..4fb5e8546831 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -1038,8 +1038,10 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp, if (likely(ret == 0)) goto open_file; - if (ret == -EEXIST) + if (ret == -EEXIST) { + nfsd_file_free(nf); goto retry; + } trace_nfsd_file_insert_err(rqstp, inode, may_flags, ret); status = nfserr_jukebox; goto construction_err;
At this point, we have a new nf that we couldn't properly insert into the hashtable. Just free it before retrying, since it was never hashed. Fixes: c6593366c0bf ("nfsd: don't kill nfsd_files because of lease break error") Signed-off-by: Jeff Layton <jlayton@kernel.org> --- fs/nfsd/filecache.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)