| Message ID | 1358755528-31421-3-git-send-email-asias@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Jan 21, 2013 at 04:05:27PM +0800, Asias He wrote: > We can get all the pages in one time instead of calling > gup N times. > > Signed-off-by: Asias He <asias@redhat.com> > --- > drivers/vhost/tcm_vhost.c | 33 ++++++++++++++++++++------------- > 1 file changed, 20 insertions(+), 13 deletions(-) > > diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c > index ca35c16..59be442 100644 > --- a/drivers/vhost/tcm_vhost.c > +++ b/drivers/vhost/tcm_vhost.c > @@ -430,37 +430,45 @@ static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd( > * Returns the number of scatterlist entries used or -errno on error. > */ > static int vhost_scsi_map_to_sgl(struct scatterlist *sgl, > - unsigned int sgl_count, void __user *ptr, size_t len, int write) > + unsigned int sgl_count, struct iovec *iov, int write) > { > struct scatterlist *sg = sgl; > unsigned int npages = 0; > + void __user *ptr = iov->iov_base; > + size_t len = iov->iov_len; > int ret; > + unsigned int pages_nr, offset, nbytes; > + struct page **pages; > + > + pages_nr = iov_num_pages(iov); > + pages = kmalloc(pages_nr * sizeof(struct page *), GFP_ATOMIC); > + if (!pages) > + return -ENOMEM; > + > + ret = get_user_pages_fast((unsigned long)ptr, pages_nr, write, pages); > + if (ret != pages_nr) > + goto err; 1. Why GFP_ATOMIC? get_user_pages_fast can sleep, so this path must not be atomic (if it is, should use __get_user_pages_fast). GFP_ATOMIC should be avoided. 2. Should drop reference to pages whose refcount has been increased, if ret > 0 && ret != pages_nr (see last phrase of get_user_pages_fast commentary). -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 01/22/2013 02:57 AM, Marcelo Tosatti wrote: > On Mon, Jan 21, 2013 at 04:05:27PM +0800, Asias He wrote: >> We can get all the pages in one time instead of calling >> gup N times. >> >> Signed-off-by: Asias He <asias@redhat.com> >> --- >> drivers/vhost/tcm_vhost.c | 33 ++++++++++++++++++++------------- >> 1 file changed, 20 insertions(+), 13 deletions(-) >> >> diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c >> index ca35c16..59be442 100644 >> --- a/drivers/vhost/tcm_vhost.c >> +++ b/drivers/vhost/tcm_vhost.c >> @@ -430,37 +430,45 @@ static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd( >> * Returns the number of scatterlist entries used or -errno on error. >> */ >> static int vhost_scsi_map_to_sgl(struct scatterlist *sgl, >> - unsigned int sgl_count, void __user *ptr, size_t len, int write) >> + unsigned int sgl_count, struct iovec *iov, int write) >> { >> struct scatterlist *sg = sgl; >> unsigned int npages = 0; >> + void __user *ptr = iov->iov_base; >> + size_t len = iov->iov_len; >> int ret; >> + unsigned int pages_nr, offset, nbytes; >> + struct page **pages; >> + >> + pages_nr = iov_num_pages(iov); >> + pages = kmalloc(pages_nr * sizeof(struct page *), GFP_ATOMIC); >> + if (!pages) >> + return -ENOMEM; >> + >> + ret = get_user_pages_fast((unsigned long)ptr, pages_nr, write, pages); >> + if (ret != pages_nr) >> + goto err; > > 1. Why GFP_ATOMIC? get_user_pages_fast can sleep, so this path must not > be atomic (if it is, should use __get_user_pages_fast). > > GFP_ATOMIC should be avoided. > > 2. Should drop reference to pages whose refcount has been increased, > if ret > 0 && ret != pages_nr (see last phrase of get_user_pages_fast > commentary). Thanks Marcelo. V2 is on the way.
diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c index ca35c16..59be442 100644 --- a/drivers/vhost/tcm_vhost.c +++ b/drivers/vhost/tcm_vhost.c @@ -430,37 +430,45 @@ static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd( * Returns the number of scatterlist entries used or -errno on error. */ static int vhost_scsi_map_to_sgl(struct scatterlist *sgl, - unsigned int sgl_count, void __user *ptr, size_t len, int write) + unsigned int sgl_count, struct iovec *iov, int write) { struct scatterlist *sg = sgl; unsigned int npages = 0; + void __user *ptr = iov->iov_base; + size_t len = iov->iov_len; int ret; + unsigned int pages_nr, offset, nbytes; + struct page **pages; + + pages_nr = iov_num_pages(iov); + pages = kmalloc(pages_nr * sizeof(struct page *), GFP_ATOMIC); + if (!pages) + return -ENOMEM; + + ret = get_user_pages_fast((unsigned long)ptr, pages_nr, write, pages); + if (ret != pages_nr) + goto err; while (len > 0) { - struct page *page; - unsigned int offset = (uintptr_t)ptr & ~PAGE_MASK; - unsigned int nbytes = min_t(unsigned int, - PAGE_SIZE - offset, len); + offset = (uintptr_t)ptr & ~PAGE_MASK; + nbytes = min_t(unsigned int, PAGE_SIZE - offset, len); if (npages == sgl_count) { ret = -ENOBUFS; goto err; } - ret = get_user_pages_fast((unsigned long)ptr, 1, write, &page); - BUG_ON(ret == 0); /* we should either get our page or fail */ - if (ret < 0) - goto err; - - sg_set_page(sg, page, nbytes, offset); + sg_set_page(sg, pages[npages], nbytes, offset); ptr += nbytes; len -= nbytes; sg++; npages++; } + kfree(pages); return npages; err: + kfree(pages); /* Put pages that we hold */ for (sg = sgl; sg != &sgl[npages]; sg++) put_page(sg_page(sg)); @@ -498,8 +506,7 @@ static int vhost_scsi_map_iov_to_sgl(struct tcm_vhost_cmd *tv_cmd, pr_debug("Mapping %u iovecs for %u pages\n", niov, sgl_count); for (i = 0; i < niov; i++) { - ret = vhost_scsi_map_to_sgl(sg, sgl_count, iov[i].iov_base, - iov[i].iov_len, write); + ret = vhost_scsi_map_to_sgl(sg, sgl_count, &iov[i], write); if (ret < 0) { for (i = 0; i < tv_cmd->tvc_sgl_count; i++) put_page(sg_page(&tv_cmd->tvc_sgl[i]));
We can get all the pages in one time instead of calling gup N times. Signed-off-by: Asias He <asias@redhat.com> --- drivers/vhost/tcm_vhost.c | 33 ++++++++++++++++++++------------- 1 file changed, 20 insertions(+), 13 deletions(-)