Hi Bruce,
Sorry for late response as well.
Ok, here's a possible patch, let me know your thoughts
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index baef5ee43dbb..1347ecae9c84 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -777,7 +777,6 @@ void cache_clean_deferred(void *owner)
*/
static DEFINE_SPINLOCK(queue_lock);
-static DEFINE_MUTEX(queue_io_mutex);
struct cache_queue {
struct list_head list;
@@ -905,44 +904,26 @@ static ssize_t cache_do_downcall(char *kaddr,
const char __user *buf,
return ret;
}
-static ssize_t cache_slow_downcall(const char __user *buf,
- size_t count, struct cache_detail *cd)
-{
- static char write_buf[8192]; /* protected by queue_io_mutex */
- ssize_t ret = -EINVAL;
-
- if (count >= sizeof(write_buf))
- goto out;
- mutex_lock(&queue_io_mutex);
- ret = cache_do_downcall(write_buf, buf, count, cd);
- mutex_unlock(&queue_io_mutex);
-out:
- return ret;
-}
-
static ssize_t cache_downcall(struct address_space *mapping,
const char __user *buf,
size_t count, struct cache_detail *cd)
{
- struct page *page;
- char *kaddr;
+ char *write_buf;
ssize_t ret = -ENOMEM;
- if (count >= PAGE_SIZE)
- goto out_slow;
+ if (count >= 32768) { /* 32k is max userland buffer, lets
check anyway */
+ ret = -EINVAL;
+ goto out;
+ }
- page = find_or_create_page(mapping, 0, GFP_KERNEL);
- if (!page)
- goto out_slow;
+ write_buf = kvmalloc(count + 1, GFP_KERNEL);
+ if (!write_buf)
+ goto out;
- kaddr = kmap(page);
- ret = cache_do_downcall(kaddr, buf, count, cd);
- kunmap(page);
- unlock_page(page);
- put_page(page);
+ ret = cache_do_downcall(write_buf, buf, count, cd);
+ kvfree(write_buf);
+out:
return ret;
-out_slow:
- return cache_slow_downcall(buf, count, cd);
}
static ssize_t cache_write(struct file *filp, const char __user *buf,
On Fri, Nov 6, 2020 at 10:51 PM J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
>
> On Mon, Oct 26, 2020 at 04:05:30PM +0100, Roberto Bergantinos Corpas wrote:
> > RPC channel buffer size for slow case (user buffer bigger than
> > one page) can be converted into dymanic and also allows us to
> > prescind from queue_io_mutex
>
> Sorry for the slow response.
>
> Let's just remove cache_slow_downcall and the find_or_create_page()
> thing and just do a kvmalloc() from the start. I don't understand why
> we need to be more complicated.
>
> --b.
>
> >
> > Signed-off-by: Roberto Bergantinos Corpas <rbergant@xxxxxxxxxx>
> > ---
> > net/sunrpc/cache.c | 13 ++++++++-----
> > 1 file changed, 8 insertions(+), 5 deletions(-)
> >
> > diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
> > index baef5ee43dbb..325393f75e17 100644
> > --- a/net/sunrpc/cache.c
> > +++ b/net/sunrpc/cache.c
> > @@ -777,7 +777,6 @@ void cache_clean_deferred(void *owner)
> > */
> >
> > static DEFINE_SPINLOCK(queue_lock);
> > -static DEFINE_MUTEX(queue_io_mutex);
> >
> > struct cache_queue {
> > struct list_head list;
> > @@ -908,14 +907,18 @@ static ssize_t cache_do_downcall(char *kaddr, const char __user *buf,
> > static ssize_t cache_slow_downcall(const char __user *buf,
> > size_t count, struct cache_detail *cd)
> > {
> > - static char write_buf[8192]; /* protected by queue_io_mutex */
> > + char *write_buf;
> > ssize_t ret = -EINVAL;
> >
> > - if (count >= sizeof(write_buf))
> > + if (count >= 32768) /* 32k is max userland buffer, lets check anyway */
> > goto out;
> > - mutex_lock(&queue_io_mutex);
> > +
> > + write_buf = kvmalloc(count + 1, GFP_KERNEL);
> > + if (!write_buf)
> > + return -ENOMEM;
> > +
> > ret = cache_do_downcall(write_buf, buf, count, cd);
> > - mutex_unlock(&queue_io_mutex);
> > + kvfree(write_buf);
> > out:
> > return ret;
> > }
> > --
> > 2.21.0
>
