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Message-Id: <20110803222548.7c1ee229.toshi.okajima@jp.fujitsu.com>
Date: Wed, 3 Aug 2011 22:25:48 +0900
From: Toshiyuki Okajima <toshi.okajima@...fujitsu.com>
To: Jan Kara <jack@...e.cz>
Cc: akpm@...ux-foundation.org, adilger.kernel@...ger.ca,
linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext3: fix message in ext3_remount for rw-remount case
Hi.
On Wed, 3 Aug 2011 11:57:54 +0200
Jan Kara <jack@...e.cz> wrote:
> Hello,
>
> On Wed 03-08-11 11:42:03, Toshiyuki Okajima wrote:
> > >(2011/08/01 18:57), Jan Kara wrote:
> > >>On Mon 01-08-11 18:45:58, Toshiyuki Okajima wrote:
> > >>>(2011/08/01 17:45), Jan Kara wrote:
> > >>>>On Mon 01-08-11 13:54:51, Toshiyuki Okajima wrote:
> > >>>>>If there are some inodes in orphan list while a filesystem is being
> > >>>>>read-only mounted, we should recommend that pepole umount and then
> > >>>>>mount it when they try to remount with read-write. But the current
> > >>>>>message/comment recommends that they umount and then remount it.
> > <SNIP>
> > >>>>the most... BTW, I guess you didn't really see this message in practice, did
> > >>>>you?
> > >>>No.
> > >>>I have seen this message in practice while quotacheck command was repeatedly
> > >>>executed per an hour.
> > >>Interesting. Are you able to reproduce this? Quotacheck does remount
> > >>read-only + remount read-write but you cannot really remount the filesystem
> > >>read-only when it has orphan inodes and so you should not see those when
> > >>you remount read-write again. Possibly there's race between remounting and
> > >>unlinking...
> > >Yes. I can reproduce it. However, it is not frequently reproduced
> > >by using the original procedure (qutacheck per an hour). So, I made a
> > >reproducer.
> > To tell the truth, I think the race creates the message:
> > -----------------------------------------------------------------------
> > EXT3-fs: <dev>: couldn't remount RDWR because of
> > unprocessed orphan inode list. Please umount/remount instead.
> > -----------------------------------------------------------------------
> > which hides a serious problem.
> I've inquired about this at linux-fsdevel (I think you were in CC unless
> I forgot). It's a race in VFS remount code as you properly analyzed below.
> People are working on fixing it but it's not trivial. Filesystem is really
> a wrong place to fix such problem. If there is a trivial fix for ext3 to
> workaround the issue, I can take it but I'm not willing to push anything
> complex - effort should better be spent working on a generic fix.
I also think read-only remount race in VFS layer should be fixed.
However, I think this race depends on ext3/ext4 filesystem
implementation. (Orphan inode list)
So, we should modify ext3/ext4(jbd/jbd2) to fix it.
>
> Honza
>
> > By using my reproducer, I found that it can show another message that
> > is not the above mentioned message:
> > -----------------------------------------------------------------------
> > EXT3-fs error (device <dev>) in start_transaction: Readonly filesystem
> > -----------------------------------------------------------------------
> > After I examined the code path which message could display, I found
> > it can display if the following steps are satisfied:
<SNIP>
> > I will try to fix this problem not to do with fs-error.
> > Please comment about the fix if I have created one.
I created a sample patch to fix above EXT3-fs error. But it is tricky,
I think. :-)
Signed-off-by: Toshiyuki Okajima <toshi.okajima@...fujitsu.com>
---
fs/ext3/inode.c | 27 ++++++++++++++++++++++-----
fs/ext3/super.c | 15 ++++++++++++++-
fs/jbd/transaction.c | 1 +
include/linux/ext3_fs.h | 3 +++
include/linux/jbd.h | 2 ++
5 files changed, 42 insertions(+), 6 deletions(-)
diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index 04da6ac..abfa500 100644
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -201,6 +201,7 @@ void ext3_evict_inode (struct inode *inode)
struct ext3_block_alloc_info *rsv;
handle_t *handle;
int want_delete = 0;
+ int err = 0;
trace_ext3_evict_inode(inode);
if (!inode->i_nlink && !is_bad_inode(inode)) {
@@ -246,6 +247,7 @@ void ext3_evict_inode (struct inode *inode)
handle = start_transaction(inode);
if (IS_ERR(handle)) {
+skip_trans:
/*
* If we're going to skip the normal cleanup, we still need to
* make sure that the in-core orphan linked list is properly
@@ -258,8 +260,13 @@ void ext3_evict_inode (struct inode *inode)
if (IS_SYNC(inode))
handle->h_sync = 1;
inode->i_size = 0;
- if (inode->i_blocks)
- ext3_truncate(inode);
+ if (inode->i_blocks) {
+ err = __ext3_truncate(inode);
+ if (err == -EROFS) {
+ ext3_journal_stop(handle);
+ goto skip_trans;
+ }
+ }
/*
* Kill off the orphan record created when the inode lost the last
* link. Note that ext3_orphan_del() has to be able to cope with the
@@ -2511,7 +2518,7 @@ int ext3_can_truncate(struct inode *inode)
* that's fine - as long as they are linked from the inode, the post-crash
* ext3_truncate() run will find them and release them.
*/
-void ext3_truncate(struct inode *inode)
+int __ext3_truncate(struct inode *inode)
{
handle_t *handle;
struct ext3_inode_info *ei = EXT3_I(inode);
@@ -2524,6 +2531,7 @@ void ext3_truncate(struct inode *inode)
int n;
long last_block;
unsigned blocksize = inode->i_sb->s_blocksize;
+ int err = 0;
trace_ext3_truncate_enter(inode);
@@ -2534,8 +2542,11 @@ void ext3_truncate(struct inode *inode)
ext3_set_inode_state(inode, EXT3_STATE_FLUSH_ON_CLOSE);
handle = start_transaction(inode);
- if (IS_ERR(handle))
+ if (IS_ERR(handle)) {
+ if (PTR_ERR(handle) == -EROFS)
+ err = -EROFS;
goto out_notrans;
+ }
last_block = (inode->i_size + blocksize-1)
>> EXT3_BLOCK_SIZE_BITS(inode->i_sb);
@@ -2654,7 +2665,7 @@ out_stop:
ext3_journal_stop(handle);
trace_ext3_truncate_exit(inode);
- return;
+ return 0;
out_notrans:
/*
* Delete the inode from orphan list so that it doesn't stay there
@@ -2663,6 +2674,12 @@ out_notrans:
if (inode->i_nlink)
ext3_orphan_del(NULL, inode);
trace_ext3_truncate_exit(inode);
+ return err;
+}
+
+void ext3_truncate(struct inode *inode)
+{
+ __ext3_truncate(inode);
}
static ext3_fsblk_t ext3_get_inode_block(struct super_block *sb,
diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index 7beb69a..22ffb04 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -270,6 +270,10 @@ void __ext3_std_error (struct super_block * sb, const char * function,
if (errno == -EROFS && journal_current_handle() == NULL &&
(sb->s_flags & MS_RDONLY))
return;
+ smp_rmb();
+ if ((sb->s_flags & MS_RDONLY) && errno == -EROFS &&
+ (EXT3_SB(sb)->s_mount_state & EXT3_ROMOUNT))
+ return;
errstr = ext3_decode_error(sb, errno, nbuf);
ext3_msg(sb, KERN_CRIT, "error in %s: %s", function, errstr);
@@ -2642,7 +2646,12 @@ static int ext3_remount (struct super_block * sb, int * flags, char * data)
* First of all, the unconditional stuff we have to do
* to disable replay of the journal when we next remount
*/
+ spin_lock(&sbi->s_journal->j_state_lock);
+ sbi->s_journal->j_flags |= JFS_ROMOUNT;
+ spin_unlock(&sbi->s_journal->j_state_lock);
+ sbi->s_mount_state |= EXT3_ROMOUNT;
sb->s_flags |= MS_RDONLY;
+ smp_wmb();
/*
* OK, test if we are remounting a valid rw partition
@@ -2651,7 +2660,8 @@ static int ext3_remount (struct super_block * sb, int * flags, char * data)
*/
if (!(es->s_state & cpu_to_le16(EXT3_VALID_FS)) &&
(sbi->s_mount_state & EXT3_VALID_FS))
- es->s_state = cpu_to_le16(sbi->s_mount_state);
+ es->s_state =
+ cpu_to_le16(sbi->s_mount_state & ~EXT3_ROMOUNT);
ext3_mark_recovery_complete(sb, es);
} else {
@@ -2686,6 +2696,9 @@ static int ext3_remount (struct super_block * sb, int * flags, char * data)
* been changed by e2fsck since we originally mounted
* the partition.)
*/
+ spin_lock(&sbi->s_journal->j_state_lock);
+ sbi->s_journal->j_flags &= ~JFS_ROMOUNT;
+ spin_unlock(&sbi->s_journal->j_state_lock);
ext3_clear_journal_err(sb, es);
sbi->s_mount_state = le16_to_cpu(es->s_state);
if ((err = ext3_group_extend(sb, es, n_blocks_count)))
diff --git a/fs/jbd/transaction.c b/fs/jbd/transaction.c
index 7e59c6e..26139a3 100644
--- a/fs/jbd/transaction.c
+++ b/fs/jbd/transaction.c
@@ -118,6 +118,7 @@ repeat:
spin_lock(&journal->j_state_lock);
repeat_locked:
if (is_journal_aborted(journal) ||
+ journal->j_flags & JFS_ROMOUNT ||
(journal->j_errno != 0 && !(journal->j_flags & JFS_ACK_ERR))) {
spin_unlock(&journal->j_state_lock);
ret = -EROFS;
diff --git a/include/linux/ext3_fs.h b/include/linux/ext3_fs.h
index 67a803a..f02ed52 100644
--- a/include/linux/ext3_fs.h
+++ b/include/linux/ext3_fs.h
@@ -369,6 +369,8 @@ struct ext3_inode {
#define EXT3_VALID_FS 0x0001 /* Unmounted cleanly */
#define EXT3_ERROR_FS 0x0002 /* Errors detected */
#define EXT3_ORPHAN_FS 0x0004 /* Orphans being recovered */
+#define EXT3_ROMOUNT 0x0008 /* FS is ro-mounted
+ * (Internal use only) */
/*
* Misc. filesystem flags
@@ -912,6 +914,7 @@ extern void ext3_dirty_inode(struct inode *, int);
extern int ext3_change_inode_journal_flag(struct inode *, int);
extern int ext3_get_inode_loc(struct inode *, struct ext3_iloc *);
extern int ext3_can_truncate(struct inode *inode);
+extern int __ext3_truncate(struct inode *inode);
extern void ext3_truncate(struct inode *inode);
extern void ext3_set_inode_flags(struct inode *);
extern void ext3_get_inode_flags(struct ext3_inode_info *);
diff --git a/include/linux/jbd.h b/include/linux/jbd.h
index e6a5e34..eae4b62 100644
--- a/include/linux/jbd.h
+++ b/include/linux/jbd.h
@@ -831,6 +831,8 @@ struct journal_s
#define JFS_ABORT_ON_SYNCDATA_ERR 0x040 /* Abort the journal on file
* data write error in ordered
* mode */
+#define JFS_ROMOUNT 0x080 /* Prevent new transaction creating
+ * while ro-mounting. */
/*
* Function declarations for the journaling transaction and buffer
--
1.5.5.6
--
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