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Message-ID: <20070205173400.GB25790@lst.de>
Date: Mon, 5 Feb 2007 18:34:00 +0100
From: Christoph Hellwig <hch@....de>
To: akpm@...l.org, haveblue@...ibm.com
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH[RFC] don't force remount in sysrq-u (emergency remount r/o)
On Mon, Feb 05, 2007 at 06:32:47PM +0100, Christoph Hellwig wrote:
> Hi there,
>
> in two recent discussions (file_list_lock scalability and remount r/o
> on suspend) I stumbled over this emergency remount feature. It's not
> actually useful because it tries a potentially dangerous remount
> despite writers still beeing in progress, which we can't get rid.
>
> I've attached one patch in this mail that simply kills the
> functionality, and in a reply to this mail I'll send a second one
> that keeps the sysrq functionality, but removes the force argument
> from do_remount_sb that overrides the still busy check. This version
> is currently not useful, but makes a lot of sense once Dave Hansens
> per-mountpoint r/o patches get in, as we can check for a real write
> in progress instead of simply a file opened with write permission.
And here is the alternate patch that simply removes the forced remount
r/o hack:
Index: linux-2.6/fs/namespace.c
===================================================================
--- linux-2.6.orig/fs/namespace.c 2007-02-05 18:21:03.000000000 +0100
+++ linux-2.6/fs/namespace.c 2007-02-05 18:21:18.000000000 +0100
@@ -597,7 +597,7 @@
if (!(sb->s_flags & MS_RDONLY)) {
lock_kernel();
DQUOT_OFF(sb);
- retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
+ retval = do_remount_sb(sb, MS_RDONLY, NULL);
unlock_kernel();
}
up_write(&sb->s_umount);
@@ -964,7 +964,7 @@
return -EINVAL;
down_write(&sb->s_umount);
- err = do_remount_sb(sb, flags, data, 0);
+ err = do_remount_sb(sb, flags, data);
if (!err)
nd->mnt->mnt_flags = mnt_flags;
up_write(&sb->s_umount);
Index: linux-2.6/fs/super.c
===================================================================
--- linux-2.6.orig/fs/super.c 2007-02-05 18:21:03.000000000 +0100
+++ linux-2.6/fs/super.c 2007-02-05 18:21:48.000000000 +0100
@@ -557,26 +557,6 @@
}
/**
- * mark_files_ro
- * @sb: superblock in question
- *
- * All files are marked read/only. We don't care about pending
- * delete files so this should be used in 'force' mode only
- */
-
-static void mark_files_ro(struct super_block *sb)
-{
- struct file *f;
-
- 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;
- }
- file_list_unlock();
-}
-
-/**
* do_remount_sb - asks filesystem to change mount options.
* @sb: superblock in question
* @flags: numeric part of options
@@ -585,7 +565,7 @@
*
* Alters the mount options of a mounted file system.
*/
-int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
+int do_remount_sb(struct super_block *sb, int flags, void *data)
{
int retval;
@@ -601,9 +581,7 @@
/* If we are remounting RDONLY and current sb is read/write,
make sure there are no rw files opened */
if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
- if (force)
- mark_files_ro(sb);
- else if (!fs_may_remount_ro(sb))
+ if (!fs_may_remount_ro(sb))
return -EBUSY;
}
@@ -634,7 +612,7 @@
* What lock protects sb->s_flags??
*/
lock_kernel();
- do_remount_sb(sb, MS_RDONLY, NULL, 1);
+ do_remount_sb(sb, MS_RDONLY, NULL);
unlock_kernel();
}
drop_super(sb);
@@ -861,7 +839,7 @@
}
s->s_flags |= MS_ACTIVE;
}
- do_remount_sb(s, flags, data, 0);
+ do_remount_sb(s, flags, data);
return simple_set_mnt(mnt, s);
}
Index: linux-2.6/include/linux/fs.h
===================================================================
--- linux-2.6.orig/include/linux/fs.h 2007-02-05 18:21:03.000000000 +0100
+++ linux-2.6/include/linux/fs.h 2007-02-05 18:21:27.000000000 +0100
@@ -1600,8 +1600,7 @@
extern void __fsync_super(struct super_block *sb);
extern void emergency_sync(void);
extern void emergency_remount(void);
-extern int do_remount_sb(struct super_block *sb, int flags,
- void *data, int force);
+extern int do_remount_sb(struct super_block *sb, int flags, void *data);
#ifdef CONFIG_BLOCK
extern sector_t bmap(struct inode *, sector_t);
#endif
-
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