From: Hugh Dickins <hugh@veritas.com>
To: Amar Lior <lior@cs.huji.ac.il>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Problem
Date: Tue, 31 Dec 2002 17:38:45 +0000 (GMT) [thread overview]
Message-ID: <Pine.LNX.4.44.0212311717400.1688-100000@localhost.localdomain> (raw)
In-Reply-To: <Pine.LNX.4.20_heb2.08.0212311818280.29471-100000@mos214.cs.huji.ac.il>
On Tue, 31 Dec 2002, Amar Lior wrote:
>
> I found a bug that cause the kernel to lockup.
In 2.4, yes. Coincidentally, Mikael Starvik reported this just a
couple of weeks ago, though it has been lurking there for a long time.
In 2.5 it was fixed (in ignorance of the problem) a little while ago,
and Marcelo already has fix below in his BK tree towards 2.4.20-pre3.
Anyway, thanks a lot for making sure we know about it. (The code was
_nearly_ right, the loop should have terminated when nr returned from
file_read_actor becomes 0: but there were _two_ declarations of nr,
and the nr tested to terminate the loop remained 1 throughout).
Hugh
diff -Nru a/mm/shmem.c b/mm/shmem.c
--- a/mm/shmem.c Thu Dec 26 22:32:38 2002
+++ b/mm/shmem.c Thu Dec 26 22:32:38 2002
@@ -919,14 +919,13 @@
struct inode *inode = filp->f_dentry->d_inode;
struct address_space *mapping = inode->i_mapping;
unsigned long index, offset;
- int nr = 1;
index = *ppos >> PAGE_CACHE_SHIFT;
offset = *ppos & ~PAGE_CACHE_MASK;
- while (nr && desc->count) {
+ for (;;) {
struct page *page;
- unsigned long end_index, nr;
+ unsigned long end_index, nr, ret;
end_index = inode->i_size >> PAGE_CACHE_SHIFT;
if (index > end_index)
@@ -956,12 +955,14 @@
* "pos" here (the actor routine has to update the user buffer
* pointers and the remaining count).
*/
- nr = file_read_actor(desc, page, offset, nr);
- offset += nr;
+ ret = file_read_actor(desc, page, offset, nr);
+ offset += ret;
index += offset >> PAGE_CACHE_SHIFT;
offset &= ~PAGE_CACHE_MASK;
page_cache_release(page);
+ if (ret != nr || !desc->count)
+ break;
}
*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
next prev parent reply other threads:[~2002-12-31 17:29 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-12-31 16:19 Problem Amar Lior
2002-12-31 17:38 ` Hugh Dickins [this message]
-- strict thread matches above, loose matches on Subject: below --
2007-04-27 1:35 PROBLEM Thomas Kayser
2006-02-03 12:02 PROBLEM Badri Pillai
2004-12-24 4:22 PROBLEM Scott Mollica
2004-12-27 3:28 ` PROBLEM Adrian Bunk
2003-12-19 18:10 PROBLEM Federico Freire
2003-12-19 18:25 ` PROBLEM Jean-Philippe Woot de Trixhe
2003-12-19 19:29 ` PROBLEM Jose Luis Domingo Lopez
2003-11-30 4:07 PROBLEM Mike Morrell
2003-11-30 6:05 ` PROBLEM Chris Ernst
2003-10-21 13:39 PROBLEM laurent.miaille
2003-03-13 21:40 Problem Smiler
2003-03-09 11:49 PROBLEM Kósa Ferenc
2003-03-09 12:55 ` PROBLEM John Bradford
2002-12-31 16:18 PROBLEM Amar Lior
2002-08-29 19:55 Problem Ryan White
2002-08-14 14:20 PROBLEM Bob Kruger
2001-09-11 23:16 Problem George Lloyd
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