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 <[EMAIL PROTECTED]>
Signed-off-by: Christoph Hellwig <[EMAIL PROTECTED]>
Signed-off-by: Dave Hansen <[EMAIL PROTECTED]>
---

 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();
 }
_
--
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