Messages in this thread | | | Date | Wed, 27 Oct 2010 12:31:48 -0700 (PDT) | From | Davide Libenzi <> | Subject | Re: [Patch] Convert max_user_watches to long. |
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On Wed, 27 Oct 2010, Robin Holt wrote:
> On a 16TB machine, max_user_watches has an integer overflow. Convert it > to use a long and handle the associated fallout.
I can't say I like adding an otherwise unused variable just to please pretty-looking, but the compiler will take care of it.
Acked-by: Davide Libenzi <davidel@xmailserver.org>
> Signed-off-by: Robin Holt <holt@sgi.com> > To: Andrew Morton <akpm@linux-foundation.org> > Cc: "Eric W. Biederman" <ebiederm@xmission.com> > Cc: Davide Libenzi <davidel@xmailserver.org> > Cc: linux-kernel@vger.kernel.org > Cc: Pekka Enberg <penberg@cs.helsinki.fi> > > --- > > fs/eventpoll.c | 20 ++++++++++++-------- > include/linux/sched.h | 2 +- > 2 files changed, 13 insertions(+), 9 deletions(-) > > Index: pv1010933/fs/eventpoll.c > =================================================================== > --- pv1010933.orig/fs/eventpoll.c 2010-10-27 14:04:44.000000000 -0500 > +++ pv1010933/fs/eventpoll.c 2010-10-27 14:07:50.211457551 -0500 > @@ -220,7 +220,7 @@ struct ep_send_events_data { > * Configuration options available inside /proc/sys/fs/epoll/ > */ > /* Maximum number of epoll watched descriptors, per user */ > -static int max_user_watches __read_mostly; > +static long max_user_watches __read_mostly; > > /* > * This mutex is used to serialize ep_free() and eventpoll_release_file(). > @@ -243,16 +243,18 @@ static struct kmem_cache *pwq_cache __re > > #include <linux/sysctl.h> > > -static int zero; > +static long zero; > +static long long_max = LONG_MAX; > > ctl_table epoll_table[] = { > { > .procname = "max_user_watches", > .data = &max_user_watches, > - .maxlen = sizeof(int), > + .maxlen = sizeof(max_user_watches), > .mode = 0644, > - .proc_handler = proc_dointvec_minmax, > + .proc_handler = proc_doulongvec_minmax, > .extra1 = &zero, > + .extra2 = &long_max, > }, > { } > }; > @@ -564,7 +566,7 @@ static int ep_remove(struct eventpoll *e > /* At this point it is safe to free the eventpoll item */ > kmem_cache_free(epi_cache, epi); > > - atomic_dec(&ep->user->epoll_watches); > + atomic_long_dec(&ep->user->epoll_watches); > > return 0; > } > @@ -900,11 +902,12 @@ static int ep_insert(struct eventpoll *e > { > int error, revents, pwake = 0; > unsigned long flags; > + long user_watches; > struct epitem *epi; > struct ep_pqueue epq; > > - if (unlikely(atomic_read(&ep->user->epoll_watches) >= > - max_user_watches)) > + user_watches = atomic_long_read(&ep->user->epoll_watches); > + if (unlikely(user_watches >= max_user_watches)) > return -ENOSPC; > if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) > return -ENOMEM; > @@ -968,7 +971,7 @@ static int ep_insert(struct eventpoll *e > > spin_unlock_irqrestore(&ep->lock, flags); > > - atomic_inc(&ep->user->epoll_watches); > + atomic_long_inc(&ep->user->epoll_watches); > > /* We have to call this outside the lock */ > if (pwake) > @@ -1422,6 +1425,7 @@ static int __init eventpoll_init(void) > */ > max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / > EP_ITEM_COST; > + BUG_ON(max_user_watches < 0); > > /* Initialize the structure used to perform safe poll wait head wake ups */ > ep_nested_calls_init(&poll_safewake_ncalls); > Index: pv1010933/include/linux/sched.h > =================================================================== > --- pv1010933.orig/include/linux/sched.h 2010-10-27 14:04:44.000000000 -0500 > +++ pv1010933/include/linux/sched.h 2010-10-27 14:04:47.119415143 -0500 > @@ -666,7 +666,7 @@ struct user_struct { > atomic_t inotify_devs; /* How many inotify devs does this user have opened? */ > #endif > #ifdef CONFIG_EPOLL > - atomic_t epoll_watches; /* The number of file descriptors currently watched */ > + atomic_long_t epoll_watches; /* The number of file descriptors currently watched */ > #endif > #ifdef CONFIG_POSIX_MQUEUE > /* protected by mq_lock */ > >
- Davide
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