| Message ID | 1ad002a1fbc2f8e48384673b0545a164afff7ce9.1646850707.git.qemu_oss@crudebyte.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | 9pfs: fix 'Twalk' protocol violation | expand |
On Mittwoch, 9. März 2022 18:57:39 CET Christian Schoenebeck wrote: > Current implementation of 'Twalk' request handling always sends an 'Rerror' > response if any error occured. The 9p2000 protocol spec sais though: > > " > If the first element cannot be walked for any reason, Rerror is returned. > Otherwise, the walk will return an Rwalk message containing nwqid qids > corresponding, in order, to the files that are visited by the nwqid > successful elementwise walks; nwqid is therefore either nwname or the > index of the first elementwise walk that failed. > " > > http://ericvh.github.io/9p-rfc/rfc9p2000.html#anchor33 > > For that reason we are no longer leaving from an error path in function > v9fs_walk(), unless really no path component could be walked successfully or > if the request has been interrupted. > > Local variable 'nvalid' counts and reflects the number of path components > successfully processed by background I/O thread, whereas local variable > 'name_idx' subsequently counts and reflects the number of path components > eventually accepted successfully by 9p server controller portion. > > New local variable 'any_err' is an aggregate variable reflecting whether any > error occurred at all, while already existing variable 'err' only reflects > the last error. > > Despite QIDs being delivered to client in a more relaxed way now, it is > important to note though that fid still must remain uneffacted if any error Typo: should be "unaffected". > occurred. > > Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com> > --- > hw/9pfs/9p.c | 29 +++++++++++++++++++++-------- > 1 file changed, 21 insertions(+), 8 deletions(-) > > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c > index 6cdc566866..8ccd180608 100644 > --- a/hw/9pfs/9p.c > +++ b/hw/9pfs/9p.c > @@ -1766,7 +1766,7 @@ static void coroutine_fn v9fs_walk(void *opaque) > { > int name_idx, nvalid; > g_autofree V9fsQID *qids = NULL; > - int i, err = 0; > + int i, err = 0, any_err = 0; > V9fsPath dpath, path; > P9ARRAY_REF(V9fsPath) pathes = NULL; > uint16_t nwnames; > @@ -1832,6 +1832,7 @@ static void coroutine_fn v9fs_walk(void *opaque) > * driver code altogether inside the following block. > */ > v9fs_co_run_in_worker({ > + nvalid = 0; > if (v9fs_request_cancelled(pdu)) { > err = -EINTR; > break; > @@ -1842,7 +1843,7 @@ static void coroutine_fn v9fs_walk(void *opaque) > break; > } > stbuf = fidst; > - for (nvalid = 0; nvalid < nwnames; nvalid++) { > + for (; nvalid < nwnames; nvalid++) { > if (v9fs_request_cancelled(pdu)) { > err = -EINTR; > break; > @@ -1874,12 +1875,13 @@ static void coroutine_fn v9fs_walk(void *opaque) > /* > * Handle all the rest of this Twalk request on main thread ... > */ > - if (err < 0) { > + if ((err < 0 && !nvalid) || err == -EINTR) { > goto out; > } > > + any_err |= err; > err = stat_to_qid(pdu, &fidst, &qid); > - if (err < 0) { > + if (err < 0 && !nvalid) { > goto out; > } > stbuf = fidst; > @@ -1888,20 +1890,30 @@ static void coroutine_fn v9fs_walk(void *opaque) > v9fs_path_copy(&dpath, &fidp->path); > v9fs_path_copy(&path, &fidp->path); > > - for (name_idx = 0; name_idx < nwnames; name_idx++) { > + for (name_idx = 0; name_idx < nvalid; name_idx++) { > if (!same_stat_id(&pdu->s->root_st, &stbuf) || > strcmp("..", wnames[name_idx].data)) > { > stbuf = stbufs[name_idx]; > err = stat_to_qid(pdu, &stbuf, &qid); > if (err < 0) { > - goto out; > + break; > } > v9fs_path_copy(&path, &pathes[name_idx]); > v9fs_path_copy(&dpath, &path); > } > memcpy(&qids[name_idx], &qid, sizeof(qid)); > } > + any_err |= err; > + if (any_err) { Not sure if there is ever the case err > 0, but as we are already comparing for "if (err < 0)" everywhere, we should probably also do the same comparison for the aggregate error variable here, right? if (any_err < 0) { ... > + if (!name_idx) { > + /* don't send any QIDs, send Rlerror instead */ > + goto out; > + } else { > + /* send QIDs (not Rlerror), but fid MUST remain unaffected */ > + goto send_qids; > + } > + } > if (fid == newfid) { > if (fidp->fid_type != P9_FID_NONE) { > err = -EINVAL; > @@ -1919,8 +1931,9 @@ static void coroutine_fn v9fs_walk(void *opaque) > newfidp->uid = fidp->uid; > v9fs_path_copy(&newfidp->path, &path); > } > - err = v9fs_walk_marshal(pdu, nwnames, qids); > - trace_v9fs_walk_return(pdu->tag, pdu->id, nwnames, qids); > +send_qids: > + err = v9fs_walk_marshal(pdu, name_idx, qids); > + trace_v9fs_walk_return(pdu->tag, pdu->id, name_idx, qids); > out: > put_fid(pdu, fidp); > if (newfidp) {
On Thu, 10 Mar 2022 10:13:33 +0100 Christian Schoenebeck <qemu_oss@crudebyte.com> wrote: > On Mittwoch, 9. März 2022 18:57:39 CET Christian Schoenebeck wrote: > > Current implementation of 'Twalk' request handling always sends an 'Rerror' > > response if any error occured. The 9p2000 protocol spec sais though: > > > > " > > If the first element cannot be walked for any reason, Rerror is returned. > > Otherwise, the walk will return an Rwalk message containing nwqid qids > > corresponding, in order, to the files that are visited by the nwqid > > successful elementwise walks; nwqid is therefore either nwname or the > > index of the first elementwise walk that failed. > > " > > > > http://ericvh.github.io/9p-rfc/rfc9p2000.html#anchor33 > > > > For that reason we are no longer leaving from an error path in function > > v9fs_walk(), unless really no path component could be walked successfully or > > if the request has been interrupted. > > > > Local variable 'nvalid' counts and reflects the number of path components > > successfully processed by background I/O thread, whereas local variable > > 'name_idx' subsequently counts and reflects the number of path components > > eventually accepted successfully by 9p server controller portion. > > > > New local variable 'any_err' is an aggregate variable reflecting whether any > > error occurred at all, while already existing variable 'err' only reflects > > the last error. > > > > Despite QIDs being delivered to client in a more relaxed way now, it is > > important to note though that fid still must remain uneffacted if any error > > Typo: should be "unaffected". > > > occurred. > > > > Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com> > > --- > > hw/9pfs/9p.c | 29 +++++++++++++++++++++-------- > > 1 file changed, 21 insertions(+), 8 deletions(-) > > > > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c > > index 6cdc566866..8ccd180608 100644 > > --- a/hw/9pfs/9p.c > > +++ b/hw/9pfs/9p.c > > @@ -1766,7 +1766,7 @@ static void coroutine_fn v9fs_walk(void *opaque) > > { > > int name_idx, nvalid; > > g_autofree V9fsQID *qids = NULL; > > - int i, err = 0; > > + int i, err = 0, any_err = 0; > > V9fsPath dpath, path; > > P9ARRAY_REF(V9fsPath) pathes = NULL; > > uint16_t nwnames; > > @@ -1832,6 +1832,7 @@ static void coroutine_fn v9fs_walk(void *opaque) > > * driver code altogether inside the following block. > > */ > > v9fs_co_run_in_worker({ > > + nvalid = 0; > > if (v9fs_request_cancelled(pdu)) { > > err = -EINTR; > > break; > > @@ -1842,7 +1843,7 @@ static void coroutine_fn v9fs_walk(void *opaque) > > break; > > } > > stbuf = fidst; > > - for (nvalid = 0; nvalid < nwnames; nvalid++) { > > + for (; nvalid < nwnames; nvalid++) { > > if (v9fs_request_cancelled(pdu)) { > > err = -EINTR; > > break; > > @@ -1874,12 +1875,13 @@ static void coroutine_fn v9fs_walk(void *opaque) > > /* > > * Handle all the rest of this Twalk request on main thread ... > > */ > > - if (err < 0) { > > + if ((err < 0 && !nvalid) || err == -EINTR) { > > goto out; > > } > > > > + any_err |= err; > > err = stat_to_qid(pdu, &fidst, &qid); > > - if (err < 0) { > > + if (err < 0 && !nvalid) { > > goto out; > > } > > stbuf = fidst; > > @@ -1888,20 +1890,30 @@ static void coroutine_fn v9fs_walk(void *opaque) > > v9fs_path_copy(&dpath, &fidp->path); > > v9fs_path_copy(&path, &fidp->path); > > > > - for (name_idx = 0; name_idx < nwnames; name_idx++) { > > + for (name_idx = 0; name_idx < nvalid; name_idx++) { > > if (!same_stat_id(&pdu->s->root_st, &stbuf) || > > strcmp("..", wnames[name_idx].data)) > > { > > stbuf = stbufs[name_idx]; > > err = stat_to_qid(pdu, &stbuf, &qid); > > if (err < 0) { > > - goto out; > > + break; > > } > > v9fs_path_copy(&path, &pathes[name_idx]); > > v9fs_path_copy(&dpath, &path); > > } > > memcpy(&qids[name_idx], &qid, sizeof(qid)); > > } > > + any_err |= err; > > + if (any_err) { > > > Not sure if there is ever the case err > 0, but as we are already comparing > for "if (err < 0)" everywhere, we should probably also do the same comparison > for the aggregate error variable here, right? > It seems that you could drop any_err and just check name_idx != nwnames ? > if (any_err < 0) { > ... > > > + if (!name_idx) { > > + /* don't send any QIDs, send Rlerror instead */ > > + goto out; > > + } else { > > + /* send QIDs (not Rlerror), but fid MUST remain unaffected */ > > + goto send_qids; > > + } > > + } > > if (fid == newfid) { > > if (fidp->fid_type != P9_FID_NONE) { > > err = -EINVAL; > > @@ -1919,8 +1931,9 @@ static void coroutine_fn v9fs_walk(void *opaque) > > newfidp->uid = fidp->uid; > > v9fs_path_copy(&newfidp->path, &path); > > } > > - err = v9fs_walk_marshal(pdu, nwnames, qids); > > - trace_v9fs_walk_return(pdu->tag, pdu->id, nwnames, qids); > > +send_qids: > > + err = v9fs_walk_marshal(pdu, name_idx, qids); > > + trace_v9fs_walk_return(pdu->tag, pdu->id, name_idx, qids); > > out: > > put_fid(pdu, fidp); > > if (newfidp) { > >
On Freitag, 11. März 2022 17:35:41 CET Greg Kurz wrote: > On Thu, 10 Mar 2022 10:13:33 +0100 > > Christian Schoenebeck <qemu_oss@crudebyte.com> wrote: > > On Mittwoch, 9. März 2022 18:57:39 CET Christian Schoenebeck wrote: > > > Current implementation of 'Twalk' request handling always sends an > > > 'Rerror' > > > > > > response if any error occured. The 9p2000 protocol spec sais though: > > > " > > > If the first element cannot be walked for any reason, Rerror is > > > returned. > > > Otherwise, the walk will return an Rwalk message containing nwqid qids > > > corresponding, in order, to the files that are visited by the nwqid > > > successful elementwise walks; nwqid is therefore either nwname or the > > > > > > index of the first elementwise walk that failed. > > > > > > " > > > > > > http://ericvh.github.io/9p-rfc/rfc9p2000.html#anchor33 > > > > > > For that reason we are no longer leaving from an error path in function > > > v9fs_walk(), unless really no path component could be walked > > > successfully or if the request has been interrupted. > > > > > > Local variable 'nvalid' counts and reflects the number of path > > > components > > > successfully processed by background I/O thread, whereas local variable > > > 'name_idx' subsequently counts and reflects the number of path > > > components > > > eventually accepted successfully by 9p server controller portion. > > > > > > New local variable 'any_err' is an aggregate variable reflecting whether > > > any error occurred at all, while already existing variable 'err' only > > > reflects the last error. > > > > > > Despite QIDs being delivered to client in a more relaxed way now, it is > > > important to note though that fid still must remain uneffacted if any > > > error > > > > Typo: should be "unaffected". > > > > > occurred. > > > > > > Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com> > > > --- > > > > > > hw/9pfs/9p.c | 29 +++++++++++++++++++++-------- > > > 1 file changed, 21 insertions(+), 8 deletions(-) > > > > > > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c > > > index 6cdc566866..8ccd180608 100644 > > > --- a/hw/9pfs/9p.c > > > +++ b/hw/9pfs/9p.c > > > @@ -1766,7 +1766,7 @@ static void coroutine_fn v9fs_walk(void *opaque) > > > > > > { > > > > > > int name_idx, nvalid; > > > g_autofree V9fsQID *qids = NULL; > > > > > > - int i, err = 0; > > > + int i, err = 0, any_err = 0; > > > > > > V9fsPath dpath, path; > > > P9ARRAY_REF(V9fsPath) pathes = NULL; > > > uint16_t nwnames; > > > > > > @@ -1832,6 +1832,7 @@ static void coroutine_fn v9fs_walk(void *opaque) > > > > > > * driver code altogether inside the following block. > > > */ > > > > > > v9fs_co_run_in_worker({ > > > > > > + nvalid = 0; > > > > > > if (v9fs_request_cancelled(pdu)) { > > > > > > err = -EINTR; > > > break; > > > > > > @@ -1842,7 +1843,7 @@ static void coroutine_fn v9fs_walk(void *opaque) > > > > > > break; > > > > > > } > > > stbuf = fidst; > > > > > > - for (nvalid = 0; nvalid < nwnames; nvalid++) { > > > + for (; nvalid < nwnames; nvalid++) { > > > > > > if (v9fs_request_cancelled(pdu)) { > > > > > > err = -EINTR; > > > break; > > > > > > @@ -1874,12 +1875,13 @@ static void coroutine_fn v9fs_walk(void *opaque) > > > > > > /* > > > > > > * Handle all the rest of this Twalk request on main thread ... > > > */ > > > > > > - if (err < 0) { > > > + if ((err < 0 && !nvalid) || err == -EINTR) { > > > > > > goto out; > > > > > > } > > > > > > + any_err |= err; > > > > > > err = stat_to_qid(pdu, &fidst, &qid); > > > > > > - if (err < 0) { > > > + if (err < 0 && !nvalid) { > > > > > > goto out; > > > > > > } > > > stbuf = fidst; > > > > > > @@ -1888,20 +1890,30 @@ static void coroutine_fn v9fs_walk(void *opaque) > > > > > > v9fs_path_copy(&dpath, &fidp->path); > > > v9fs_path_copy(&path, &fidp->path); > > > > > > - for (name_idx = 0; name_idx < nwnames; name_idx++) { > > > + for (name_idx = 0; name_idx < nvalid; name_idx++) { > > > > > > if (!same_stat_id(&pdu->s->root_st, &stbuf) || > > > > > > strcmp("..", wnames[name_idx].data)) > > > > > > { > > > > > > stbuf = stbufs[name_idx]; > > > err = stat_to_qid(pdu, &stbuf, &qid); > > > if (err < 0) { > > > > > > - goto out; > > > + break; > > > > > > } > > > v9fs_path_copy(&path, &pathes[name_idx]); > > > v9fs_path_copy(&dpath, &path); > > > > > > } > > > memcpy(&qids[name_idx], &qid, sizeof(qid)); > > > > > > } > > > > > > + any_err |= err; > > > + if (any_err) { > > > > Not sure if there is ever the case err > 0, but as we are already > > comparing > > for "if (err < 0)" everywhere, we should probably also do the same > > comparison for the aggregate error variable here, right? > > It seems that you could drop any_err and just check name_idx != nwnames ? Mmm, what about the special case 'Twalk nwnames=0' (i.e. fid cloning), that implementation would then skip errors, no? > > if (any_err < 0) { > > > > ... > > > > > > + if (!name_idx) { > > > + /* don't send any QIDs, send Rlerror instead */ > > > + goto out; > > > + } else { > > > + /* send QIDs (not Rlerror), but fid MUST remain unaffected > > > */ > > > + goto send_qids; > > > + } > > > + } > > > > > > if (fid == newfid) { > > > > > > if (fidp->fid_type != P9_FID_NONE) { > > > > > > err = -EINVAL; > > > > > > @@ -1919,8 +1931,9 @@ static void coroutine_fn v9fs_walk(void *opaque) > > > > > > newfidp->uid = fidp->uid; > > > v9fs_path_copy(&newfidp->path, &path); > > > > > > } > > > > > > - err = v9fs_walk_marshal(pdu, nwnames, qids); > > > - trace_v9fs_walk_return(pdu->tag, pdu->id, nwnames, qids); > > > +send_qids: > > > + err = v9fs_walk_marshal(pdu, name_idx, qids); > > > + trace_v9fs_walk_return(pdu->tag, pdu->id, name_idx, qids); > > > > > > out: > > > put_fid(pdu, fidp); > > > if (newfidp) {
On Fri, 11 Mar 2022 17:44:54 +0100 Christian Schoenebeck <qemu_oss@crudebyte.com> wrote: > On Freitag, 11. März 2022 17:35:41 CET Greg Kurz wrote: > > On Thu, 10 Mar 2022 10:13:33 +0100 > > > > Christian Schoenebeck <qemu_oss@crudebyte.com> wrote: > > > On Mittwoch, 9. März 2022 18:57:39 CET Christian Schoenebeck wrote: > > > > Current implementation of 'Twalk' request handling always sends an > > > > 'Rerror' > > > > > > > > response if any error occured. The 9p2000 protocol spec sais though: > > > > " > > > > If the first element cannot be walked for any reason, Rerror is > > > > returned. > > > > Otherwise, the walk will return an Rwalk message containing nwqid qids > > > > corresponding, in order, to the files that are visited by the nwqid > > > > successful elementwise walks; nwqid is therefore either nwname or the > > > > > > > > index of the first elementwise walk that failed. > > > > > > > > " > > > > > > > > http://ericvh.github.io/9p-rfc/rfc9p2000.html#anchor33 > > > > > > > > For that reason we are no longer leaving from an error path in function > > > > v9fs_walk(), unless really no path component could be walked > > > > successfully or if the request has been interrupted. > > > > > > > > Local variable 'nvalid' counts and reflects the number of path > > > > components > > > > successfully processed by background I/O thread, whereas local variable > > > > 'name_idx' subsequently counts and reflects the number of path > > > > components > > > > eventually accepted successfully by 9p server controller portion. > > > > > > > > New local variable 'any_err' is an aggregate variable reflecting whether > > > > any error occurred at all, while already existing variable 'err' only > > > > reflects the last error. > > > > > > > > Despite QIDs being delivered to client in a more relaxed way now, it is > > > > important to note though that fid still must remain uneffacted if any > > > > error > > > > > > Typo: should be "unaffected". > > > > > > > occurred. > > > > > > > > Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com> > > > > --- > > > > > > > > hw/9pfs/9p.c | 29 +++++++++++++++++++++-------- > > > > 1 file changed, 21 insertions(+), 8 deletions(-) > > > > > > > > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c > > > > index 6cdc566866..8ccd180608 100644 > > > > --- a/hw/9pfs/9p.c > > > > +++ b/hw/9pfs/9p.c > > > > @@ -1766,7 +1766,7 @@ static void coroutine_fn v9fs_walk(void *opaque) > > > > > > > > { > > > > > > > > int name_idx, nvalid; > > > > g_autofree V9fsQID *qids = NULL; > > > > > > > > - int i, err = 0; > > > > + int i, err = 0, any_err = 0; > > > > > > > > V9fsPath dpath, path; > > > > P9ARRAY_REF(V9fsPath) pathes = NULL; > > > > uint16_t nwnames; > > > > > > > > @@ -1832,6 +1832,7 @@ static void coroutine_fn v9fs_walk(void *opaque) > > > > > > > > * driver code altogether inside the following block. > > > > */ > > > > > > > > v9fs_co_run_in_worker({ > > > > > > > > + nvalid = 0; > > > > > > > > if (v9fs_request_cancelled(pdu)) { > > > > > > > > err = -EINTR; > > > > break; > > > > > > > > @@ -1842,7 +1843,7 @@ static void coroutine_fn v9fs_walk(void *opaque) > > > > > > > > break; > > > > > > > > } > > > > stbuf = fidst; > > > > > > > > - for (nvalid = 0; nvalid < nwnames; nvalid++) { > > > > + for (; nvalid < nwnames; nvalid++) { > > > > > > > > if (v9fs_request_cancelled(pdu)) { > > > > > > > > err = -EINTR; > > > > break; > > > > > > > > @@ -1874,12 +1875,13 @@ static void coroutine_fn v9fs_walk(void *opaque) > > > > > > > > /* > > > > > > > > * Handle all the rest of this Twalk request on main thread ... > > > > */ > > > > > > > > - if (err < 0) { > > > > + if ((err < 0 && !nvalid) || err == -EINTR) { > > > > > > > > goto out; > > > > > > > > } > > > > > > > > + any_err |= err; > > > > > > > > err = stat_to_qid(pdu, &fidst, &qid); > > > > > > > > - if (err < 0) { > > > > + if (err < 0 && !nvalid) { > > > > > > > > goto out; > > > > > > > > } > > > > stbuf = fidst; > > > > > > > > @@ -1888,20 +1890,30 @@ static void coroutine_fn v9fs_walk(void *opaque) > > > > > > > > v9fs_path_copy(&dpath, &fidp->path); > > > > v9fs_path_copy(&path, &fidp->path); > > > > > > > > - for (name_idx = 0; name_idx < nwnames; name_idx++) { > > > > + for (name_idx = 0; name_idx < nvalid; name_idx++) { > > > > > > > > if (!same_stat_id(&pdu->s->root_st, &stbuf) || > > > > > > > > strcmp("..", wnames[name_idx].data)) > > > > > > > > { > > > > > > > > stbuf = stbufs[name_idx]; > > > > err = stat_to_qid(pdu, &stbuf, &qid); > > > > if (err < 0) { > > > > > > > > - goto out; > > > > + break; > > > > > > > > } > > > > v9fs_path_copy(&path, &pathes[name_idx]); > > > > v9fs_path_copy(&dpath, &path); > > > > > > > > } > > > > memcpy(&qids[name_idx], &qid, sizeof(qid)); > > > > > > > > } > > > > > > > > + any_err |= err; > > > > + if (any_err) { > > > > > > Not sure if there is ever the case err > 0, but as we are already > > > comparing > > > for "if (err < 0)" everywhere, we should probably also do the same > > > comparison for the aggregate error variable here, right? > > > > It seems that you could drop any_err and just check name_idx != nwnames ? > > Mmm, what about the special case 'Twalk nwnames=0' (i.e. fid cloning), that > implementation would then skip errors, no? > Ouch you're right... honestly, v9fs_walk() is really a mess and it is getting harder to fix. What about having a totally separate path for the cloning case (as a preparatory patch) ? > > > if (any_err < 0) { > > > > > > ... > > > > > > > > + if (!name_idx) { > > > > + /* don't send any QIDs, send Rlerror instead */ > > > > + goto out; > > > > + } else { > > > > + /* send QIDs (not Rlerror), but fid MUST remain unaffected > > > > */ > > > > + goto send_qids; > > > > + } > > > > + } > > > > > > > > if (fid == newfid) { > > > > > > > > if (fidp->fid_type != P9_FID_NONE) { > > > > > > > > err = -EINVAL; > > > > > > > > @@ -1919,8 +1931,9 @@ static void coroutine_fn v9fs_walk(void *opaque) > > > > > > > > newfidp->uid = fidp->uid; > > > > v9fs_path_copy(&newfidp->path, &path); > > > > > > > > } > > > > > > > > - err = v9fs_walk_marshal(pdu, nwnames, qids); > > > > - trace_v9fs_walk_return(pdu->tag, pdu->id, nwnames, qids); > > > > +send_qids: > > > > + err = v9fs_walk_marshal(pdu, name_idx, qids); > > > > + trace_v9fs_walk_return(pdu->tag, pdu->id, name_idx, qids); > > > > > > > > out: > > > > put_fid(pdu, fidp); > > > > if (newfidp) { > >
On Freitag, 11. März 2022 18:08:38 CET Greg Kurz wrote: > On Fri, 11 Mar 2022 17:44:54 +0100 > > Christian Schoenebeck <qemu_oss@crudebyte.com> wrote: > > On Freitag, 11. März 2022 17:35:41 CET Greg Kurz wrote: > > > On Thu, 10 Mar 2022 10:13:33 +0100 > > > > > > Christian Schoenebeck <qemu_oss@crudebyte.com> wrote: > > > > On Mittwoch, 9. März 2022 18:57:39 CET Christian Schoenebeck wrote: > > > > > Current implementation of 'Twalk' request handling always sends an > > > > > 'Rerror' > > > > > > > > > > response if any error occured. The 9p2000 protocol spec sais though: > > > > > " > > > > > If the first element cannot be walked for any reason, Rerror is > > > > > returned. > > > > > Otherwise, the walk will return an Rwalk message containing nwqid > > > > > qids > > > > > corresponding, in order, to the files that are visited by the > > > > > nwqid > > > > > successful elementwise walks; nwqid is therefore either nwname or > > > > > the > > > > > > > > > > index of the first elementwise walk that failed. > > > > > > > > > > " > > > > > > > > > > http://ericvh.github.io/9p-rfc/rfc9p2000.html#anchor33 > > > > > > > > > > For that reason we are no longer leaving from an error path in > > > > > function > > > > > v9fs_walk(), unless really no path component could be walked > > > > > successfully or if the request has been interrupted. > > > > > > > > > > Local variable 'nvalid' counts and reflects the number of path > > > > > components > > > > > successfully processed by background I/O thread, whereas local > > > > > variable > > > > > 'name_idx' subsequently counts and reflects the number of path > > > > > components > > > > > eventually accepted successfully by 9p server controller portion. > > > > > > > > > > New local variable 'any_err' is an aggregate variable reflecting > > > > > whether > > > > > any error occurred at all, while already existing variable 'err' > > > > > only > > > > > reflects the last error. > > > > > > > > > > Despite QIDs being delivered to client in a more relaxed way now, it > > > > > is > > > > > important to note though that fid still must remain uneffacted if > > > > > any > > > > > error > > > > > > > > Typo: should be "unaffected". > > > > > > > > > occurred. > > > > > > > > > > Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com> > > > > > --- > > > > > > > > > > hw/9pfs/9p.c | 29 +++++++++++++++++++++-------- > > > > > 1 file changed, 21 insertions(+), 8 deletions(-) > > > > > > > > > > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c > > > > > index 6cdc566866..8ccd180608 100644 > > > > > --- a/hw/9pfs/9p.c > > > > > +++ b/hw/9pfs/9p.c > > > > > @@ -1766,7 +1766,7 @@ static void coroutine_fn v9fs_walk(void > > > > > *opaque) > > > > > > > > > > { > > > > > > > > > > int name_idx, nvalid; > > > > > g_autofree V9fsQID *qids = NULL; > > > > > > > > > > - int i, err = 0; > > > > > + int i, err = 0, any_err = 0; > > > > > > > > > > V9fsPath dpath, path; > > > > > P9ARRAY_REF(V9fsPath) pathes = NULL; > > > > > uint16_t nwnames; > > > > > > > > > > @@ -1832,6 +1832,7 @@ static void coroutine_fn v9fs_walk(void > > > > > *opaque) > > > > > > > > > > * driver code altogether inside the following block. > > > > > */ > > > > > > > > > > v9fs_co_run_in_worker({ > > > > > > > > > > + nvalid = 0; > > > > > > > > > > if (v9fs_request_cancelled(pdu)) { > > > > > > > > > > err = -EINTR; > > > > > break; > > > > > > > > > > @@ -1842,7 +1843,7 @@ static void coroutine_fn v9fs_walk(void > > > > > *opaque) > > > > > > > > > > break; > > > > > > > > > > } > > > > > stbuf = fidst; > > > > > > > > > > - for (nvalid = 0; nvalid < nwnames; nvalid++) { > > > > > + for (; nvalid < nwnames; nvalid++) { > > > > > > > > > > if (v9fs_request_cancelled(pdu)) { > > > > > > > > > > err = -EINTR; > > > > > break; > > > > > > > > > > @@ -1874,12 +1875,13 @@ static void coroutine_fn v9fs_walk(void > > > > > *opaque) > > > > > > > > > > /* > > > > > > > > > > * Handle all the rest of this Twalk request on main thread ... > > > > > */ > > > > > > > > > > - if (err < 0) { > > > > > + if ((err < 0 && !nvalid) || err == -EINTR) { > > > > > > > > > > goto out; > > > > > > > > > > } > > > > > > > > > > + any_err |= err; > > > > > > > > > > err = stat_to_qid(pdu, &fidst, &qid); > > > > > > > > > > - if (err < 0) { > > > > > + if (err < 0 && !nvalid) { > > > > > > > > > > goto out; > > > > > > > > > > } > > > > > stbuf = fidst; > > > > > > > > > > @@ -1888,20 +1890,30 @@ static void coroutine_fn v9fs_walk(void > > > > > *opaque) > > > > > > > > > > v9fs_path_copy(&dpath, &fidp->path); > > > > > v9fs_path_copy(&path, &fidp->path); > > > > > > > > > > - for (name_idx = 0; name_idx < nwnames; name_idx++) { > > > > > + for (name_idx = 0; name_idx < nvalid; name_idx++) { > > > > > > > > > > if (!same_stat_id(&pdu->s->root_st, &stbuf) || > > > > > > > > > > strcmp("..", wnames[name_idx].data)) > > > > > > > > > > { > > > > > > > > > > stbuf = stbufs[name_idx]; > > > > > err = stat_to_qid(pdu, &stbuf, &qid); > > > > > if (err < 0) { > > > > > > > > > > - goto out; > > > > > + break; > > > > > > > > > > } > > > > > v9fs_path_copy(&path, &pathes[name_idx]); > > > > > v9fs_path_copy(&dpath, &path); > > > > > > > > > > } > > > > > memcpy(&qids[name_idx], &qid, sizeof(qid)); > > > > > > > > > > } > > > > > > > > > > + any_err |= err; > > > > > + if (any_err) { > > > > > > > > Not sure if there is ever the case err > 0, but as we are already > > > > comparing > > > > for "if (err < 0)" everywhere, we should probably also do the same > > > > comparison for the aggregate error variable here, right? > > > > > > It seems that you could drop any_err and just check name_idx != nwnames > > > ? > > > > Mmm, what about the special case 'Twalk nwnames=0' (i.e. fid cloning), > > that > > implementation would then skip errors, no? > > Ouch you're right... honestly, v9fs_walk() is really a mess and it > is getting harder to fix. What about having a totally separate > path for the cloning case (as a preparatory patch) ? You suggested that before, somehow I did not get to simpler code when trying that, rather the opposite. But you definitely have a better eye on identifying redundant pathes than me. There are some things that can still be wiped away, like the path vs. dpath variables, but I thought to do that a bit later. Best regards, Christian Schoenebeck
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c index 6cdc566866..8ccd180608 100644 --- a/hw/9pfs/9p.c +++ b/hw/9pfs/9p.c @@ -1766,7 +1766,7 @@ static void coroutine_fn v9fs_walk(void *opaque) { int name_idx, nvalid; g_autofree V9fsQID *qids = NULL; - int i, err = 0; + int i, err = 0, any_err = 0; V9fsPath dpath, path; P9ARRAY_REF(V9fsPath) pathes = NULL; uint16_t nwnames; @@ -1832,6 +1832,7 @@ static void coroutine_fn v9fs_walk(void *opaque) * driver code altogether inside the following block. */ v9fs_co_run_in_worker({ + nvalid = 0; if (v9fs_request_cancelled(pdu)) { err = -EINTR; break; @@ -1842,7 +1843,7 @@ static void coroutine_fn v9fs_walk(void *opaque) break; } stbuf = fidst; - for (nvalid = 0; nvalid < nwnames; nvalid++) { + for (; nvalid < nwnames; nvalid++) { if (v9fs_request_cancelled(pdu)) { err = -EINTR; break; @@ -1874,12 +1875,13 @@ static void coroutine_fn v9fs_walk(void *opaque) /* * Handle all the rest of this Twalk request on main thread ... */ - if (err < 0) { + if ((err < 0 && !nvalid) || err == -EINTR) { goto out; } + any_err |= err; err = stat_to_qid(pdu, &fidst, &qid); - if (err < 0) { + if (err < 0 && !nvalid) { goto out; } stbuf = fidst; @@ -1888,20 +1890,30 @@ static void coroutine_fn v9fs_walk(void *opaque) v9fs_path_copy(&dpath, &fidp->path); v9fs_path_copy(&path, &fidp->path); - for (name_idx = 0; name_idx < nwnames; name_idx++) { + for (name_idx = 0; name_idx < nvalid; name_idx++) { if (!same_stat_id(&pdu->s->root_st, &stbuf) || strcmp("..", wnames[name_idx].data)) { stbuf = stbufs[name_idx]; err = stat_to_qid(pdu, &stbuf, &qid); if (err < 0) { - goto out; + break; } v9fs_path_copy(&path, &pathes[name_idx]); v9fs_path_copy(&dpath, &path); } memcpy(&qids[name_idx], &qid, sizeof(qid)); } + any_err |= err; + if (any_err) { + if (!name_idx) { + /* don't send any QIDs, send Rlerror instead */ + goto out; + } else { + /* send QIDs (not Rlerror), but fid MUST remain unaffected */ + goto send_qids; + } + } if (fid == newfid) { if (fidp->fid_type != P9_FID_NONE) { err = -EINVAL; @@ -1919,8 +1931,9 @@ static void coroutine_fn v9fs_walk(void *opaque) newfidp->uid = fidp->uid; v9fs_path_copy(&newfidp->path, &path); } - err = v9fs_walk_marshal(pdu, nwnames, qids); - trace_v9fs_walk_return(pdu->tag, pdu->id, nwnames, qids); +send_qids: + err = v9fs_walk_marshal(pdu, name_idx, qids); + trace_v9fs_walk_return(pdu->tag, pdu->id, name_idx, qids); out: put_fid(pdu, fidp); if (newfidp) {
Current implementation of 'Twalk' request handling always sends an 'Rerror' response if any error occured. The 9p2000 protocol spec sais though: " If the first element cannot be walked for any reason, Rerror is returned. Otherwise, the walk will return an Rwalk message containing nwqid qids corresponding, in order, to the files that are visited by the nwqid successful elementwise walks; nwqid is therefore either nwname or the index of the first elementwise walk that failed. " http://ericvh.github.io/9p-rfc/rfc9p2000.html#anchor33 For that reason we are no longer leaving from an error path in function v9fs_walk(), unless really no path component could be walked successfully or if the request has been interrupted. Local variable 'nvalid' counts and reflects the number of path components successfully processed by background I/O thread, whereas local variable 'name_idx' subsequently counts and reflects the number of path components eventually accepted successfully by 9p server controller portion. New local variable 'any_err' is an aggregate variable reflecting whether any error occurred at all, while already existing variable 'err' only reflects the last error. Despite QIDs being delivered to client in a more relaxed way now, it is important to note though that fid still must remain uneffacted if any error occurred. Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com> --- hw/9pfs/9p.c | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-)