[PATCH 09/30] r/o bind mounts: drop write during emergency remount

Dave Hansen
2008-02-15T22:40:33Z

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() to keep everything
balanced.

Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
---

linux-2.6.git-dave/fs/super.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)

diff -puN fs/super.c~robind-sysrq-fix fs/super.c
--- linux-2.6.git/fs/super.c~robind-sysrq-fix 2008-02-15 13:25:46.000000000 -0800
+++ linux-2.6.git-dave/fs/super.c 2008-02-15 13:25:46.000000000 -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>

@@ -567,10 +568,25 @@ 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;
+ 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();
}
_