Messages in this thread | | | Date | Wed, 3 Dec 2008 00:35:17 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH v2] hugetlb: unsigned ret cannot be negative. |
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On Tue, 02 Dec 2008 23:51:06 +0100 Roel Kluin <roel.kluin@gmail.com> wrote:
> Andrew Morton wrote: > > On Sat, 29 Nov 2008 06:36:59 -0500 > > roel kluin <roel.kluin@gmail.com> wrote: > > > >> unsigned long ret cannot be negative, but ret can get -EFAULT. > >> > >> Signed-off-by: Roel Kluin <roel.kluin@gmail.com> > >> --- > >> hugetlbfs_read_actor() returns int, > >> see > >> vi fs/hugetlbfs/inode.c +187 > >> > >> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > >> index 61edc70..0af64e4 100644 > >> --- a/fs/hugetlbfs/inode.c > >> +++ b/fs/hugetlbfs/inode.c > >> @@ -252,6 +252,7 @@ static ssize_t hugetlbfs_read(struct file *filp, char __user *buf, > >> for (;;) { > >> struct page *page; > >> unsigned long nr, ret; > >> + int ra; > >> > >> /* nr is the maximum number of bytes to copy from this page */ > >> nr = huge_page_size(h); > >> @@ -279,15 +280,16 @@ static ssize_t hugetlbfs_read(struct file *filp, char __user *buf, > >> /* > >> * We have the page, copy it to user space buffer. > >> */ > >> - ret = hugetlbfs_read_actor(page, offset, buf, len, nr); > >> + ra = hugetlbfs_read_actor(page, offset, buf, len, nr); > >> } > >> - if (ret < 0) { > >> + if (ra < 0) { > > > `ra' can obviously be used uninitialised here. The compiler reports > > this, too. > > Yes, it was incomplete as well, sorry. This should be OK. > (checkpatch tested) > --------------->8----------------8<--------------------- > unsigned long ret cannot be negative, but ret can get -EFAULT. > > Signed-off-by: Roel Kluin <roel.kluin@gmail.com> > --- > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > index 61edc70..07fa7e3 100644 > --- a/fs/hugetlbfs/inode.c > +++ b/fs/hugetlbfs/inode.c > @@ -252,6 +252,7 @@ static ssize_t hugetlbfs_read(struct file *filp, char __user *buf, > for (;;) { > struct page *page; > unsigned long nr, ret; > + int ra; > > /* nr is the maximum number of bytes to copy from this page */ > nr = huge_page_size(h); > @@ -274,16 +275,19 @@ static ssize_t hugetlbfs_read(struct file *filp, char __user *buf, > */ > ret = len < nr ? len : nr; > if (clear_user(buf, ret)) > - ret = -EFAULT; > + ra = -EFAULT; > + else > + ra = 0; > } else { > /* > * We have the page, copy it to user space buffer. > */ > - ret = hugetlbfs_read_actor(page, offset, buf, len, nr); > + ra = hugetlbfs_read_actor(page, offset, buf, len, nr); > + ret = ra; > } > - if (ret < 0) { > + if (ra < 0) { > if (retval == 0) > - retval = ret; > + retval = ra; > if (page) > page_cache_release(page); > goto out;
Looks like it'll work, I think.
That function is pretty sad-looking now. It has `ra', `ret' and `retval', all rather confusingly. After being renamed to something useful, `ret' should have type size_t, hugetlbfs_read_actor() should return size_t and the whole logic around these three things needs a can of drano tipped down it.
Oh well.
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