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authorCarsten Otte <cotte@de.ibm.com>2009-02-11 13:04:37 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-02-11 14:25:36 -0800
commit0e4a9b59282914fe057ab17027f55123964bc2e2 (patch)
tree8bf359a1937e809d767f73f7ccdb948420ae72fc /fs
parentcfebe563bd0a3ff97e1bc167123120d59c7a84db (diff)
downloadlinux-0e4a9b59282914fe057ab17027f55123964bc2e2.tar.gz
ext2/xip: refuse to change xip flag during remount with busy inodes
For a reason that I was unable to understand in three months of debugging, mount ext2 -o remount stopped working properly when remounting from regular operation to xip, or the other way around. According to a git bisect search, the problem was introduced with the VM_MIXEDMAP/PTE_SPECIAL rework in the vm: commit 70688e4dd1647f0ceb502bbd5964fa344c5eb411 Author: Nick Piggin <npiggin@suse.de> Date: Mon Apr 28 02:13:02 2008 -0700 xip: support non-struct page backed memory In the failing scenario, the filesystem is mounted read only via root= kernel parameter on s390x. During remount (in rc.sysinit), the inodes of the bash binary and its libraries are busy and cannot be invalidated (the bash which is running rc.sysinit resides on subject filesystem). Afterwards, another bash process (running ifup-eth) recurses into a subshell, runs dup_mm (via fork). Some of the mappings in this bash process were created from inodes that could not be invalidated during remount. Both parent and child process crash some time later due to inconsistencies in their address spaces. The issue seems to be timing sensitive, various attempts to recreate it have failed. This patch refuses to change the xip flag during remount in case some inodes cannot be invalidated. This patch keeps users from running into that issue. [akpm@linux-foundation.org: cleanup] Signed-off-by: Carsten Otte <cotte@de.ibm.com> Cc: Nick Piggin <npiggin@suse.de> Cc: Jared Hulbert <jaredeh@gmail.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/ext2/super.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index da8bdeaa2e6..7c6e3606f0e 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -1185,9 +1185,12 @@ static int ext2_remount (struct super_block * sb, int * flags, char * data)
es = sbi->s_es;
if (((sbi->s_mount_opt & EXT2_MOUNT_XIP) !=
(old_mount_opt & EXT2_MOUNT_XIP)) &&
- invalidate_inodes(sb))
- ext2_warning(sb, __func__, "busy inodes while remounting "\
- "xip remain in cache (no functional problem)");
+ invalidate_inodes(sb)) {
+ ext2_warning(sb, __func__, "refusing change of xip flag "
+ "with busy inodes while remounting");
+ sbi->s_mount_opt &= ~EXT2_MOUNT_XIP;
+ sbi->s_mount_opt |= old_mount_opt & EXT2_MOUNT_XIP;
+ }
if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
return 0;
if (*flags & MS_RDONLY) {