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[PATCH 26/30] r/o bind mounts: check mnt instead of superblock directly

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From: Dave Hansen <haveblue@...>
To: <linux-kernel@...>
Cc: <hch@...>, <miklos@...>, <akpm@...>, Dave Hansen <haveblue@...>
Subject: [PATCH 26/30] r/o bind mounts: check mnt instead of superblock directly
Date: Friday, February 15, 2008 - 6:37 pm

If we depend on the inodes for writeability, we will not catch the r/o mounts
when implemented.

This patches uses __mnt_want_write().  It does not guarantee that the mount
will stay writeable after the check.  But, this is OK for one of the checks
because it is just for a printk().

The other two are probably unnecessary and duplicate existing checks in the
VFS.  This won't make them better checks than before, but it will make them
detect r/o mounts.

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 linux-2.6.git-dave/fs/nfs/dir.c  |    3 ++-
 linux-2.6.git-dave/fs/nfsd/vfs.c |    5 +++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff -puN fs/nfs/dir.c~r-o-bind-mounts-nfs-check-mnt-instead-of-superblock-directly fs/nfs/dir.c
--- linux-2.6.git/fs/nfs/dir.c~r-o-bind-mounts-nfs-check-mnt-instead-of-superblock-directly	2008-02-15 13:25:57.000000000 -0800
+++ linux-2.6.git-dave/fs/nfs/dir.c	2008-02-15 13:25:57.000000000 -0800
@@ -967,7 +967,8 @@ static int is_atomic_open(struct inode *
 	if (nd->flags & LOOKUP_DIRECTORY)
 		return 0;
 	/* Are we trying to write to a read only partition? */
-	if (IS_RDONLY(dir) && (nd->intent.open.flags & (O_CREAT|O_TRUNC|FMODE_WRITE)))
+	if (__mnt_is_readonly(nd->mnt) &&
+	    (nd->intent.open.flags & (O_CREAT|O_TRUNC|FMODE_WRITE)))
 		return 0;
 	return 1;
 }
diff -puN fs/nfsd/vfs.c~r-o-bind-mounts-nfs-check-mnt-instead-of-superblock-directly fs/nfsd/vfs.c
--- linux-2.6.git/fs/nfsd/vfs.c~r-o-bind-mounts-nfs-check-mnt-instead-of-superblock-directly	2008-02-15 13:25:57.000000000 -0800
+++ linux-2.6.git-dave/fs/nfsd/vfs.c	2008-02-15 13:25:57.000000000 -0800
@@ -1874,7 +1874,7 @@ nfsd_permission(struct svc_rqst *rqstp, 
 		inode->i_mode,
 		IS_IMMUTABLE(inode)?	" immut" : "",
 		IS_APPEND(inode)?	" append" : "",
-		IS_RDONLY(inode)?	" ro" : "");
+		__mnt_is_readonly(exp->ex_mnt)?	" ro" : "");
 	dprintk("      owner %d/%d user %d/%d\n",
 		inode->i_uid, inode->i_gid, current->fsuid, current->fsgid);
 #endif
@@ -1885,7 +1885,8 @@ nfsd_permission(struct svc_rqst *rqstp, 
 	 */
 	if (!(acc & MAY_LOCAL_ACCESS))
 		if (acc & (MAY_WRITE | MAY_SATTR | MAY_TRUNC)) {
-			if (exp_rdonly(rqstp, exp) || IS_RDONLY(inode))
+			if (exp_rdonly(rqstp, exp) ||
+			    __mnt_is_readonly(exp->ex_mnt))
 				return nfserr_rofs;
 			if (/* (acc & MAY_WRITE) && */ IS_IMMUTABLE(inode))
 				return nfserr_perm;
_
--
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Messages in current thread:
[PATCH 00/30] Read-only bind mounts (-mm resend), Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH] r/o bind mounts: stub functions, Dave Hansen, (Fri Feb 15, 9:32 pm)
[PATCH 30/30] r/o bind mounts: debugging for missed calls, Dave Hansen, (Fri Feb 15, 6:38 pm)
[PATCH 29/30] r/o bind mounts: honor mount writer counts at ..., Dave Hansen, (Fri Feb 15, 6:38 pm)
[PATCH 28/30] r/o bind mounts: track numbers of writers to m..., Dave Hansen, (Fri Feb 15, 6:37 pm)
Re: [PATCH 28/30] r/o bind mounts: track numbers of writers ..., Miklos Szeredi, (Mon Feb 18, 12:10 pm)
Re: [PATCH 28/30] r/o bind mounts: track numbers of writers ..., Dave Hansen, (Wed Feb 20, 5:12 pm)
[PATCH 27/30] r/o bind mounts: get callers of vfs_mknod/crea..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 26/30] r/o bind mounts: check mnt instead of superblo..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 22/30] r/o bind mounts: elevate write count for chmod..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 25/30] r/o bind mounts: make access() use new r/o hel..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 24/30] r/o bind mounts: elevate count for xfs timesta..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 23/30] r/o bind mounts: write counts for truncate(), Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 21/30] r/o bind mounts: get write access for vfs_rena..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 20/30] r/o bind mounts: elevate write count for open()s, Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 19/30] r/o bind mounts: elevate write count for ioctl..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 18/30] r/o bind mounts: write counts for link/symlink, Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 17/30] r/o bind mounts: write count for file_update_t..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 06/30] merge open_namei() and do_filp_open(), Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 16/30] r/o bind mounts: elevate write count for do_ut..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 15/30] r/o bind mounts: write counts for time functions, Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 14/30] r/o bind mounts: elevate write count for ncp_i..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 13/30] r/o bind mounts: elevate write count for xattr..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 12/30] r/o bind mounts: elevate mnt_writers for unlin..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 11/30] r/o bind mounts: elevate write count for calle..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 10/30] r/o bind mounts: elevate write count for vfs_r..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 08/30] r/o bind mounts: create helper to drop file wr..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 05/30] do namei_flags calculation inside open_namei(), Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 03/30] check for null vfsmount in dentry_open(), Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 07/30] r/o bind mounts: stub functions, Dave Hansen, (Fri Feb 15, 6:37 pm)
Re: [PATCH 07/30] r/o bind mounts: stub functions, Theodore Tso, (Fri Feb 15, 8:32 pm)
Re: [PATCH 07/30] r/o bind mounts: stub functions, Dave Hansen, (Fri Feb 15, 8:49 pm)
Re: [PATCH 07/30] r/o bind mounts: stub functions, Theodore Tso, (Fri Feb 15, 9:00 pm)
Re: [PATCH 07/30] r/o bind mounts: stub functions, Andrew Morton, (Fri Feb 15, 9:11 pm)
Re: [PATCH 07/30] r/o bind mounts: stub functions, Christoph Hellwig, (Sat Feb 16, 2:31 am)
Re: [PATCH 07/30] r/o bind mounts: stub functions, Dave Hansen, (Wed Feb 20, 6:25 pm)
Re: [PATCH 07/30] r/o bind mounts: stub functions, Christoph Hellwig, (Wed Feb 20, 6:58 pm)
Re: [PATCH 07/30] r/o bind mounts: stub functions, Andrew Morton, (Sat Feb 16, 2:46 am)
Re: [PATCH 07/30] r/o bind mounts: stub functions, Dave Hansen, (Mon Feb 18, 3:06 am)
[PATCH 09/30] r/o bind mounts: drop write during emergency r..., Dave Hansen, (Fri Feb 15, 6:37 pm)
Re: [PATCH 09/30] r/o bind mounts: drop write during emergen..., Miklos Szeredi, (Mon Feb 18, 12:29 pm)
Re: [PATCH 09/30] r/o bind mounts: drop write during emergen..., Al Viro, (Sat Feb 23, 9:38 am)
[PATCH 01/30] reiserfs: eliminate private use of struct file..., Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 04/30] fix up new filp allocators, Dave Hansen, (Fri Feb 15, 6:37 pm)
[PATCH 02/30] hppfs pass vfsmount to dentry_open(), Dave Hansen, (Fri Feb 15, 6:37 pm)