<div dir="ltr"><div dir="ltr"> </div> <div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Apr 27, 2021 at 1:01 PM Dr. David Alan Gilbert <<a href="mailto:dgilbert@redhat.com">dgilbert@redhat.com</a>> wrote: </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">* Mahmoud Mandour (<a href="mailto:ma.mandourr@gmail.com" target="_blank">ma.mandourr@gmail.com</a>) wrote: > On Tue, Apr 27, 2021 at 12:25 PM Dr. David Alan Gilbert <<a href="mailto:dgilbert@redhat.com" target="_blank">dgilbert@redhat.com</a>> > wrote: > > > * Mahmoud Mandour (<a href="mailto:ma.mandourr@gmail.com" target="_blank">ma.mandourr@gmail.com</a>) wrote: > > > Replaced the calls to malloc()/calloc() and their respective > > > calls to free() of iovec structs with GLib's allocation and > > > deallocation functions. > > > > > > Also, in one instance, used g_new0() instead of a calloc() call plus > > > a null-checking assertion. > > > > > > iovec structs were created locally and freed as the function > > > ends. Hence, I used g_autofree and removed the respective calls to > > > free(). > > > > > > In one instance, a struct fuse_ioctl_iovec pointer is returned from a > > > function, namely, fuse_ioctl_iovec_copy. There, I used g_steal_pointer() > > > in conjunction with g_autofree, this gives the ownership of the pointer > > > to the calling function and still auto-frees the memory when the calling > > > function finishes (maintaining the symantics of previous code). > > > > > > Signed-off-by: Mahmoud Mandour <<a href="mailto:ma.mandourr@gmail.com" target="_blank">ma.mandourr@gmail.com</a>> > > > Reviewed-by: Stefan Hajnoczi <<a href="mailto:stefanha@redhat.com" target="_blank">stefanha@redhat.com</a>> > > > --- > > > tools/virtiofsd/fuse_lowlevel.c | 19 +++++++------------ > > > tools/virtiofsd/fuse_virtio.c | 6 +----- > > > 2 files changed, 8 insertions(+), 17 deletions(-) > > > > > > diff --git a/tools/virtiofsd/fuse_lowlevel.c > > b/tools/virtiofsd/fuse_lowlevel.c > > > index 812cef6ef6..f965299ad9 100644 > > > --- a/tools/virtiofsd/fuse_lowlevel.c > > > +++ b/tools/virtiofsd/fuse_lowlevel.c > > > @@ -217,9 +217,9 @@ static int send_reply(fuse_req_t req, int error, > > const void *arg, > > > int fuse_reply_iov(fuse_req_t req, const struct iovec *iov, int count) > > > { > > > int res; > > > - struct iovec *padded_iov; > > > + g_autofree struct iovec *padded_iov; > > > > > > - padded_iov = malloc((count + 1) * sizeof(struct iovec)); > > > + padded_iov = g_try_new(struct iovec, count + 1); > > > if (padded_iov == NULL) { > > > return fuse_reply_err(req, ENOMEM); > > > } > > > @@ -228,7 +228,6 @@ int fuse_reply_iov(fuse_req_t req, const struct > > iovec *iov, int count) > > > count++; > > > > > > res = send_reply_iov(req, 0, padded_iov, count); > > > - free(padded_iov); > > > > > > return res; > > > } > > > > OK. > > > > > @@ -565,10 +564,10 @@ int fuse_reply_bmap(fuse_req_t req, uint64_t idx) > > > static struct fuse_ioctl_iovec *fuse_ioctl_iovec_copy(const struct > > iovec *iov, > > > size_t count) > > > { > > > - struct fuse_ioctl_iovec *fiov; > > > + g_autofree struct fuse_ioctl_iovec *fiov; > > > size_t i; > > > > > > - fiov = malloc(sizeof(fiov[0]) * count); > > > + fiov = g_try_new(fuse_ioctl_iovec, count); > > > if (!fiov) { > > > return NULL; > > > } > > > @@ -578,7 +577,7 @@ static struct fuse_ioctl_iovec > > *fuse_ioctl_iovec_copy(const struct iovec *iov, > > > fiov[i].len = iov[i].iov_len; > > > } > > > > > > - return fiov; > > > + return g_steal_pointer(&fiov); > > > } > > > > This is OK, but doesn't gain anything - marking it as g_autofree'ing and > > always stealing is no benefit. > > > > > > > > int fuse_reply_ioctl_retry(fuse_req_t req, const struct iovec *in_iov, > > > @@ -629,9 +628,6 @@ int fuse_reply_ioctl_retry(fuse_req_t req, const > > struct iovec *in_iov, > > > > > > res = send_reply_iov(req, 0, iov, count); > > > out: > > > - free(in_fiov); > > > - free(out_fiov); > > > - > > > > I don't think you can do that - I think you're relying here on the > > g_autofree from fuse_ioclt_iovec_copy - but my understanding is that > > doesn't work; g_autofree is scoped, so it's designed to free at the end > > of fuse_ioctl_iovec_copy, fuse_reply_ioctl_retry doesn't know that the > > ion_fiov were allocated that way, so it won't get autocleaned up. > > > > > In GLib's documentation, it is clarified (w.r.t. g_autoptr but I think > similar logic applies to g_autofree) > that g_steal_pointer() "This can be very useful when combined with > g_autoptr() to prevent > the return value of a function from being automatically freed." > I think, but not 100% clear of course, that this means that the > g_autoptr-annotated memory > does not get freed at the end of the current scope, and its "scope" is > migrated to the calling > function(to be honest I don't know how would they implement that but maybe > this is the case). > Otherwise why bother with g_autoptr'ing memory that we don't want to free > automatically and > would like to return to the calling function? > > The first example in Memory Allocation: GLib Reference Manual (<a href="http://gnome.org" rel="noreferrer" target="_blank">gnome.org</a>) > <<a href="https://developer.gnome.org/glib/stable/glib-Memory-Allocation.html#g-steal-pointer" rel="noreferrer" target="_blank">https://developer.gnome.org/glib/stable/glib-Memory-Allocation.html#g-steal-pointer</a>> > does > annotate > the memory as g_autoptr and then returns it through g_steal_pointer. With > your logic, I think that > this example would be wrong(?) The example is correct but not quite the case you have; the g_steal_pointer stops the g_autoptr freeing it at the end of the current scope; but it doesn't cause it to be free'd later - the caller can't tell that the function that did the allocation had a g_autofree in it; once you get outside of the function, the pointer is just a normal pointer that needs free or g_free on. </blockquote><div>I think that this is logical, yes. I think that I understand now. Can you please instruct</div><div>me on what to do with the patch? Do you want me to resend the entire patch series</div><div>and amend this one?</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"> > Mr. Hajnoczi already reviewed this patch Re: [PATCH 2/8] virtiofds: > Changed allocations of iovec to GLib's functi > <<a href="https://lists.gnu.org/archive/html/qemu-devel/2021-03/msg08459.html" rel="noreferrer" target="_blank">https://lists.gnu.org/archive/html/qemu-devel/2021-03/msg08459.html</a>> > in a previous version and this v2 patch series is supposed to only contain > already-reviewed patches and > remove bad ones But he didn't spot this particular problem. Dave > > > > return res; > > > > > > enomem: > > > @@ -663,11 +659,11 @@ int fuse_reply_ioctl(fuse_req_t req, int result, > > const void *buf, size_t size) > > > int fuse_reply_ioctl_iov(fuse_req_t req, int result, const struct iovec > > *iov, > > > int count) > > > { > > > - struct iovec *padded_iov; > > > + g_autofree struct iovec *padded_iov; > > > struct fuse_ioctl_out arg; > > > int res; > > > > > > - padded_iov = malloc((count + 2) * sizeof(struct iovec)); > > > + padded_iov = g_try_new(struct iovec, count + 2); > > > if (padded_iov == NULL) { > > > return fuse_reply_err(req, ENOMEM); > > > } > > > @@ -680,7 +676,6 @@ int fuse_reply_ioctl_iov(fuse_req_t req, int result, > > const struct iovec *iov, > > > memcpy(&padded_iov[2], iov, count * sizeof(struct iovec)); > > > > > > res = send_reply_iov(req, 0, padded_iov, count + 2); > > > - free(padded_iov); > > > > > > return res; > > > } > > > > OK > > > > > diff --git a/tools/virtiofsd/fuse_virtio.c > > b/tools/virtiofsd/fuse_virtio.c > > > index 3e13997406..07e5d91a9f 100644 > > > --- a/tools/virtiofsd/fuse_virtio.c > > > +++ b/tools/virtiofsd/fuse_virtio.c > > > @@ -347,8 +347,7 @@ int virtio_send_data_iov(struct fuse_session *se, > > struct fuse_chan *ch, > > > * Build a copy of the the in_sg iov so we can skip bits in it, > > > * including changing the offsets > > > */ > > > - struct iovec *in_sg_cpy = calloc(sizeof(struct iovec), in_num); > > > - assert(in_sg_cpy); > > > + g_autofree struct iovec *in_sg_cpy = g_new0(struct iovec, in_num); > > > memcpy(in_sg_cpy, in_sg, sizeof(struct iovec) * in_num); > > > /* These get updated as we skip */ > > > struct iovec *in_sg_ptr = in_sg_cpy; > > > @@ -386,7 +385,6 @@ int virtio_send_data_iov(struct fuse_session *se, > > struct fuse_chan *ch, > > > ret = errno; > > > fuse_log(FUSE_LOG_DEBUG, "%s: preadv failed (%m) len=%zd\n", > > > __func__, len); > > > - free(in_sg_cpy); > > > goto err; > > > } > > > fuse_log(FUSE_LOG_DEBUG, "%s: preadv ret=%d len=%zd\n", > > __func__, > > > @@ -410,13 +408,11 @@ int virtio_send_data_iov(struct fuse_session *se, > > struct fuse_chan *ch, > > > if (ret != len) { > > > fuse_log(FUSE_LOG_DEBUG, "%s: ret!=len\n", __func__); > > > ret = EIO; > > > - free(in_sg_cpy); > > > goto err; > > > } > > > in_sg_left -= ret; > > > len -= ret; > > > } while (in_sg_left); > > > - free(in_sg_cpy); > > > > Yes, this is where the autofree really helps; getting rid of a few > > free's. > > > > Dave > > > > > /* Need to fix out->len on EOF */ > > > if (len) { > > > -- > > > 2.25.1 > > > > > -- > > Dr. David Alan Gilbert / <a href="mailto:dgilbert@redhat.com" target="_blank">dgilbert@redhat.com</a> / Manchester, UK > > > > > Thanks, > Mahmoud -- Dr. David Alan Gilbert / <a href="mailto:dgilbert@redhat.com" target="_blank">dgilbert@redhat.com</a> / Manchester, UK </blockquote><div> </div><div>Thanks,</div><div>Mahmoud </div></div></div>