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SubjectRe: 2.6.24-rc8-mm1: sparc64 warning at fs/file_table.c:49 __fput+0x1a8/0x1e0()
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On Tue, 2008-01-22 at 13:02 -0800, Andrew Morton wrote:
> > On Tue, 22 Jan 2008 21:30:23 +0100 Mariusz Kozlowski <m.kozlowski@tuxland.pl> wrote:
> > Hello,
> >
> > Issuing "sysrq-s sysrq-u" sequence causes these warnings on sparc64:
> >
> > ------------[ cut here ]------------
> > WARNING: at fs/file_table.c:49 __fput+0x1a8/0x1e0()
> > Modules linked in: sg sr_mod cdrom
> > Call Trace:
> > [00000000004c9ac8] __fput+0x1b0/0x1e0
> > [00000000004c6978] filp_close+0x60/0x80
> > [00000000004c6a18] sys_close+0x80/0xe0
> > [00000000004062d4] linux_sparc_syscall32+0x3c/0x40
> > [0000000000012f1c] 0x12f24
> > ---[ end trace 6dbe14ff8ec57744 ]---
> > ------------[ cut here ]------------
...
> That's
>
> WARN_ON(f->f_mnt_write_state == FILE_MNT_WRITE_TAKEN);


The emergency remount code forcibly removes FMODE_WRITE from
filps. The r/o bind mount code notices that this was done
without a proper mnt_drop_write() and properly gives a
warning.

This patch does a mnt_drop_write() and also notes in the
filp that this was done to suppress any warning that would
have otherwise been triggered.

I also wonder if inode->i_writecount is made inconsistent
by the emergency remount code. I guess it is, but the
damage is limited to a single inode instead of being
visible more globally like the mnt write count. Probably
not really worth fixing.

BTW, this wasn't just a sparc thing. I triggered it in about
3 seconds on a plain old x86 machine.

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
---
linux-2.6.git-dave/fs/super.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff -puN fs/super.c~robind-sysrq-fix fs/super.c
--- linux-2.6.git/fs/super.c~robind-sysrq-fix 2008-01-22 14:33:38.000000000 -0800
+++ linux-2.6.git-dave/fs/super.c 2008-01-22 14:51:13.000000000 -0800
@@ -37,6 +37,7 @@
#include <linux/idr.h>
#include <linux/kobject.h>
#include <linux/mutex.h>
+#include <linux/file.h>
#include <asm/uaccess.h>


@@ -566,10 +567,26 @@ static void mark_files_ro(struct super_b
{
struct file *f;

+retry:
file_list_lock();
list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
- if (S_ISREG(f->f_path.dentry->d_inode->i_mode) && file_count(f))
- f->f_mode &= ~FMODE_WRITE;
+ struct vfsmount mnt;
+ if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
+ continue;
+ if (!file_count(f))
+ continue;
+ if (!(f->f_mode & FMODE_WRITE))
+ continue;
+ f->f_mode &= ~FMODE_WRITE;
+ f->f_mnt_write_state |= FILE_MNT_WRITE_RELEASED;
+ mnt = f->f_path.mnt;
+ file_list_unlock();
+ /*
+ * This can sleep, so we can't hold
+ * the file_list_lock() spinlock.
+ */
+ mnt_drop_write(mnt);
+ goto retry;
}
file_list_unlock();
}
_

-- Dave



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