[PATCH] ext4: handle errors on ext4_commit_super

[PATCH] ext4: handle errors on ext4_commit_super

[Jaegeuk Kim]

From: Jaegeuk Kim <jaegeuk@google.com>

When remounting ext4 from ro to rw, currently it allows its transition,
even if ext4_commit_super() returns EIO. Even worse thing is, after that,
fs/buffer complains buffer dirty bits like:

 Call trace:
 [<ffffff9750c259dc>] mark_buffer_dirty+0x184/0x1a4
 [<ffffff9750cb398c>] __ext4_handle_dirty_super+0x4c/0xfc
 [<ffffff9750c7a9fc>] ext4_file_open+0x154/0x1c0
 [<ffffff9750bea51c>] do_dentry_open+0x114/0x2d0
 [<ffffff9750bea75c>] vfs_open+0x5c/0x94
 [<ffffff9750bf879c>] path_openat+0x668/0xfe8
 [<ffffff9750bf8088>] do_filp_open+0x74/0x120
 [<ffffff9750beac98>] do_sys_open+0x148/0x254
 [<ffffff9750beade0>] SyS_openat+0x10/0x18
 [<ffffff9750a83ab0>] el0_svc_naked+0x24/0x28
 EXT4-fs (dm-1): previous I/O error to superblock detected
 Buffer I/O error on dev dm-1, logical block 0, lost sync page write
 EXT4-fs (dm-1): re-mounted. Opts: (null)
 Buffer I/O error on dev dm-1, logical block 80, lost async page write

Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: linux-ext4@vger.kernel.org
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>
---
 fs/ext4/super.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 39bf464c35f1..b268bfea879c 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2151,7 +2151,7 @@ static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
 	if (sbi->s_journal)
 		ext4_set_feature_journal_needs_recovery(sb);
 
-	ext4_commit_super(sb, 1);
+	res = ext4_commit_super(sb, 1);
 done:
 	if (test_opt(sb, DEBUG))
 		printk(KERN_INFO "[EXT4 FS bs=%lu, gc=%u, "
@@ -4739,11 +4739,10 @@ static int ext4_commit_super(struct super_block *sb, int sync)
 		unlock_buffer(sbh);
 		error = __sync_dirty_buffer(sbh,
 			REQ_SYNC | (test_opt(sb, BARRIER) ? REQ_FUA : 0));
-		if (error)
+		if (error && !buffer_write_io_error(sbh))
 			return error;
 
-		error = buffer_write_io_error(sbh);
-		if (error) {
+		if (buffer_write_io_error(sbh)) {
 			ext4_msg(sb, KERN_ERR, "I/O error while writing "
 			       "superblock");
 			clear_buffer_write_io_error(sbh);
@@ -5144,8 +5143,12 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 			if (sbi->s_journal)
 				ext4_clear_journal_err(sb, es);
 			sbi->s_mount_state = le16_to_cpu(es->s_state);
-			if (!ext4_setup_super(sb, es, 0))
-				sb->s_flags &= ~SB_RDONLY;
+
+			err = ext4_setup_super(sb, es, 0);
+			if (err)
+				goto restore_opts;
+
+			sb->s_flags &= ~SB_RDONLY;
 			if (ext4_has_feature_mmp(sb))
 				if (ext4_multi_mount_protect(sb,
 						le64_to_cpu(es->s_mmp_block))) {
@@ -5169,8 +5172,10 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 	}
 
 	ext4_setup_system_zone(sb);
-	if (sbi->s_journal == NULL && !(old_sb_flags & SB_RDONLY))
-		ext4_commit_super(sb, 1);
+	if (sbi->s_journal == NULL && !(old_sb_flags & SB_RDONLY)) {
+		err = ext4_commit_super(sb, 1);
+		goto restore_opts;
+	}
 
 #ifdef CONFIG_QUOTA
 	/* Release old quota file names */
-- 
2.15.0.531.g2ccb3012c9-goog

Re: [PATCH] ext4: handle errors on ext4_commit_super

[Jan Kara]

On Thu 29-03-18 18:44:29, Jaegeuk Kim wrote:
> From: Jaegeuk Kim <jaegeuk@google.com>
> 
> When remounting ext4 from ro to rw, currently it allows its transition,
> even if ext4_commit_super() returns EIO. Even worse thing is, after that,
> fs/buffer complains buffer dirty bits like:
> 
>  Call trace:
>  [<ffffff9750c259dc>] mark_buffer_dirty+0x184/0x1a4
>  [<ffffff9750cb398c>] __ext4_handle_dirty_super+0x4c/0xfc
>  [<ffffff9750c7a9fc>] ext4_file_open+0x154/0x1c0
>  [<ffffff9750bea51c>] do_dentry_open+0x114/0x2d0
>  [<ffffff9750bea75c>] vfs_open+0x5c/0x94
>  [<ffffff9750bf879c>] path_openat+0x668/0xfe8
>  [<ffffff9750bf8088>] do_filp_open+0x74/0x120
>  [<ffffff9750beac98>] do_sys_open+0x148/0x254
>  [<ffffff9750beade0>] SyS_openat+0x10/0x18
>  [<ffffff9750a83ab0>] el0_svc_naked+0x24/0x28
>  EXT4-fs (dm-1): previous I/O error to superblock detected
>  Buffer I/O error on dev dm-1, logical block 0, lost sync page write
>  EXT4-fs (dm-1): re-mounted. Opts: (null)
>  Buffer I/O error on dev dm-1, logical block 80, lost async page write
> 
> Cc: "Theodore Ts'o" <tytso@mit.edu>
> Cc: Andreas Dilger <adilger.kernel@dilger.ca>
> Cc: linux-ext4@vger.kernel.org
> Cc: Jaegeuk Kim <jaegeuk@kernel.org>
> Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>
> ---
>  fs/ext4/super.c | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)

Thanks for the patch. Some comments below.

> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 39bf464c35f1..b268bfea879c 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -2151,7 +2151,7 @@ static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
>  	if (sbi->s_journal)
>  		ext4_set_feature_journal_needs_recovery(sb);
>  
> -	ext4_commit_super(sb, 1);
> +	res = ext4_commit_super(sb, 1);
>  done:
>  	if (test_opt(sb, DEBUG))
>  		printk(KERN_INFO "[EXT4 FS bs=%lu, gc=%u, "

So return value of ext4_setup_super() looks a bit strange and it seems it
currently returns 0 or SB_RDONLY. So I think you first need to clean this
up before making ext4_setup_super() return error code (as your patch could
make ext4_fill_super() return SB_RDONLY under some circumstances).

> @@ -4739,11 +4739,10 @@ static int ext4_commit_super(struct super_block *sb, int sync)
>  		unlock_buffer(sbh);
>  		error = __sync_dirty_buffer(sbh,
>  			REQ_SYNC | (test_opt(sb, BARRIER) ? REQ_FUA : 0));
> -		if (error)
> +		if (error && !buffer_write_io_error(sbh))
>  			return error;
>  
> -		error = buffer_write_io_error(sbh);
> -		if (error) {
> +		if (buffer_write_io_error(sbh)) {
>  			ext4_msg(sb, KERN_ERR, "I/O error while writing "
>  			       "superblock");
>  			clear_buffer_write_io_error(sbh);

I'd rather rewrite this as:
		if (buffer_write_io_error(sbh)) {
			do stuff as now
		}
		if (error)
			return error;

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH] ext4: handle errors on ext4_commit_super

[Jaegeuk Kim]

Hi Jan,

Thank you for the review.

On 04/19, Jan Kara wrote:
> On Thu 29-03-18 18:44:29, Jaegeuk Kim wrote:
> > From: Jaegeuk Kim <jaegeuk@google.com>
> > 
> > When remounting ext4 from ro to rw, currently it allows its transition,
> > even if ext4_commit_super() returns EIO. Even worse thing is, after that,
> > fs/buffer complains buffer dirty bits like:
> > 
> >  Call trace:
> >  [<ffffff9750c259dc>] mark_buffer_dirty+0x184/0x1a4
> >  [<ffffff9750cb398c>] __ext4_handle_dirty_super+0x4c/0xfc
> >  [<ffffff9750c7a9fc>] ext4_file_open+0x154/0x1c0
> >  [<ffffff9750bea51c>] do_dentry_open+0x114/0x2d0
> >  [<ffffff9750bea75c>] vfs_open+0x5c/0x94
> >  [<ffffff9750bf879c>] path_openat+0x668/0xfe8
> >  [<ffffff9750bf8088>] do_filp_open+0x74/0x120
> >  [<ffffff9750beac98>] do_sys_open+0x148/0x254
> >  [<ffffff9750beade0>] SyS_openat+0x10/0x18
> >  [<ffffff9750a83ab0>] el0_svc_naked+0x24/0x28
> >  EXT4-fs (dm-1): previous I/O error to superblock detected
> >  Buffer I/O error on dev dm-1, logical block 0, lost sync page write
> >  EXT4-fs (dm-1): re-mounted. Opts: (null)
> >  Buffer I/O error on dev dm-1, logical block 80, lost async page write
> > 
> > Cc: "Theodore Ts'o" <tytso@mit.edu>
> > Cc: Andreas Dilger <adilger.kernel@dilger.ca>
> > Cc: linux-ext4@vger.kernel.org
> > Cc: Jaegeuk Kim <jaegeuk@kernel.org>
> > Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>
> > ---
> >  fs/ext4/super.c | 21 +++++++++++++--------
> >  1 file changed, 13 insertions(+), 8 deletions(-)
> 
> Thanks for the patch. Some comments below.
> 
> > 
> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > index 39bf464c35f1..b268bfea879c 100644
> > --- a/fs/ext4/super.c
> > +++ b/fs/ext4/super.c
> > @@ -2151,7 +2151,7 @@ static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
> >  	if (sbi->s_journal)
> >  		ext4_set_feature_journal_needs_recovery(sb);
> >  
> > -	ext4_commit_super(sb, 1);
> > +	res = ext4_commit_super(sb, 1);
> >  done:
> >  	if (test_opt(sb, DEBUG))
> >  		printk(KERN_INFO "[EXT4 FS bs=%lu, gc=%u, "
> 
> So return value of ext4_setup_super() looks a bit strange and it seems it
> currently returns 0 or SB_RDONLY. So I think you first need to clean this

Indeed. I'll update it in v2.

> up before making ext4_setup_super() return error code (as your patch could
> make ext4_fill_super() return SB_RDONLY under some circumstances).

Interestingly, it only affects ext4_remount() only. :P

> 
> > @@ -4739,11 +4739,10 @@ static int ext4_commit_super(struct super_block *sb, int sync)
> >  		unlock_buffer(sbh);
> >  		error = __sync_dirty_buffer(sbh,
> >  			REQ_SYNC | (test_opt(sb, BARRIER) ? REQ_FUA : 0));
> > -		if (error)
> > +		if (error && !buffer_write_io_error(sbh))
> >  			return error;
> >  
> > -		error = buffer_write_io_error(sbh);
> > -		if (error) {
> > +		if (buffer_write_io_error(sbh)) {
> >  			ext4_msg(sb, KERN_ERR, "I/O error while writing "
> >  			       "superblock");
> >  			clear_buffer_write_io_error(sbh);
> 
> I'd rather rewrite this as:
> 		if (buffer_write_io_error(sbh)) {
> 			do stuff as now
> 		}
> 		if (error)
> 			return error;

Got it.

Thanks,

> 
> 								Honza
> -- 
> Jan Kara <jack@suse.com>
> SUSE Labs, CR

Re: [PATCH v2] ext4: handle errors on ext4_commit_super

[Jaegeuk Kim]

When remounting ext4 from ro to rw, currently it allows its transition,
even if ext4_commit_super() returns EIO. Even worse thing is, after that,
fs/buffer complains buffer dirty bits like:

 Call trace:
 [<ffffff9750c259dc>] mark_buffer_dirty+0x184/0x1a4
 [<ffffff9750cb398c>] __ext4_handle_dirty_super+0x4c/0xfc
 [<ffffff9750c7a9fc>] ext4_file_open+0x154/0x1c0
 [<ffffff9750bea51c>] do_dentry_open+0x114/0x2d0
 [<ffffff9750bea75c>] vfs_open+0x5c/0x94
 [<ffffff9750bf879c>] path_openat+0x668/0xfe8
 [<ffffff9750bf8088>] do_filp_open+0x74/0x120
 [<ffffff9750beac98>] do_sys_open+0x148/0x254
 [<ffffff9750beade0>] SyS_openat+0x10/0x18
 [<ffffff9750a83ab0>] el0_svc_naked+0x24/0x28
 EXT4-fs (dm-1): previous I/O error to superblock detected
 Buffer I/O error on dev dm-1, logical block 0, lost sync page write
 EXT4-fs (dm-1): re-mounted. Opts: (null)
 Buffer I/O error on dev dm-1, logical block 80, lost async page write

Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: linux-ext4@vger.kernel.org
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>
---

Change log from v1:
 - modify return value of ext4_setup_super
 - change the error handling order in ext4_commit_super

 fs/ext4/super.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 185f7e61f4cf..af4d373aa3ed 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2116,12 +2116,12 @@ static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
 			    int read_only)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
-	int res = 0;
+	int err = 0;
 
 	if (le32_to_cpu(es->s_rev_level) > EXT4_MAX_SUPP_REV) {
 		ext4_msg(sb, KERN_ERR, "revision level too high, "
 			 "forcing read-only mode");
-		res = SB_RDONLY;
+		err = -EROFS;
 	}
 	if (read_only)
 		goto done;
@@ -2154,7 +2154,7 @@ static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
 	if (sbi->s_journal)
 		ext4_set_feature_journal_needs_recovery(sb);
 
-	ext4_commit_super(sb, 1);
+	err = ext4_commit_super(sb, 1);
 done:
 	if (test_opt(sb, DEBUG))
 		printk(KERN_INFO "[EXT4 FS bs=%lu, gc=%u, "
@@ -2166,7 +2166,7 @@ static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
 			sbi->s_mount_opt, sbi->s_mount_opt2);
 
 	cleancache_init_fs(sb);
-	return res;
+	return err;
 }
 
 int ext4_alloc_flex_bg_array(struct super_block *sb, ext4_group_t ngroup)
@@ -4760,11 +4760,7 @@ static int ext4_commit_super(struct super_block *sb, int sync)
 		unlock_buffer(sbh);
 		error = __sync_dirty_buffer(sbh,
 			REQ_SYNC | (test_opt(sb, BARRIER) ? REQ_FUA : 0));
-		if (error)
-			return error;
-
-		error = buffer_write_io_error(sbh);
-		if (error) {
+		if (buffer_write_io_error(sbh)) {
 			ext4_msg(sb, KERN_ERR, "I/O error while writing "
 			       "superblock");
 			clear_buffer_write_io_error(sbh);
@@ -5165,8 +5161,12 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 			if (sbi->s_journal)
 				ext4_clear_journal_err(sb, es);
 			sbi->s_mount_state = le16_to_cpu(es->s_state);
-			if (!ext4_setup_super(sb, es, 0))
-				sb->s_flags &= ~SB_RDONLY;
+
+			err = ext4_setup_super(sb, es, 0);
+			if (err)
+				goto restore_opts;
+
+			sb->s_flags &= ~SB_RDONLY;
 			if (ext4_has_feature_mmp(sb))
 				if (ext4_multi_mount_protect(sb,
 						le64_to_cpu(es->s_mmp_block))) {
@@ -5190,8 +5190,10 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 	}
 
 	ext4_setup_system_zone(sb);
-	if (sbi->s_journal == NULL && !(old_sb_flags & SB_RDONLY))
-		ext4_commit_super(sb, 1);
+	if (sbi->s_journal == NULL && !(old_sb_flags & SB_RDONLY)) {
+		err = ext4_commit_super(sb, 1);
+		goto restore_opts;
+	}
 
 #ifdef CONFIG_QUOTA
 	/* Release old quota file names */
-- 
2.17.0.484.g0c8726318c-goog

Re: [PATCH v2] ext4: handle errors on ext4_commit_super

[Jan Kara]

On Thu 19-04-18 08:59:57, Jaegeuk Kim wrote:
> When remounting ext4 from ro to rw, currently it allows its transition,
> even if ext4_commit_super() returns EIO. Even worse thing is, after that,
> fs/buffer complains buffer dirty bits like:
> 
>  Call trace:
>  [<ffffff9750c259dc>] mark_buffer_dirty+0x184/0x1a4
>  [<ffffff9750cb398c>] __ext4_handle_dirty_super+0x4c/0xfc
>  [<ffffff9750c7a9fc>] ext4_file_open+0x154/0x1c0
>  [<ffffff9750bea51c>] do_dentry_open+0x114/0x2d0
>  [<ffffff9750bea75c>] vfs_open+0x5c/0x94
>  [<ffffff9750bf879c>] path_openat+0x668/0xfe8
>  [<ffffff9750bf8088>] do_filp_open+0x74/0x120
>  [<ffffff9750beac98>] do_sys_open+0x148/0x254
>  [<ffffff9750beade0>] SyS_openat+0x10/0x18
>  [<ffffff9750a83ab0>] el0_svc_naked+0x24/0x28
>  EXT4-fs (dm-1): previous I/O error to superblock detected
>  Buffer I/O error on dev dm-1, logical block 0, lost sync page write
>  EXT4-fs (dm-1): re-mounted. Opts: (null)
>  Buffer I/O error on dev dm-1, logical block 80, lost async page write
> 
> Cc: "Theodore Ts'o" <tytso@mit.edu>
> Cc: Andreas Dilger <adilger.kernel@dilger.ca>
> Cc: linux-ext4@vger.kernel.org
> Cc: Jaegeuk Kim <jaegeuk@kernel.org>
> Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>

Looks mostly good. Just:

> @@ -5190,8 +5190,10 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
>  	}
>  
>  	ext4_setup_system_zone(sb);
> -	if (sbi->s_journal == NULL && !(old_sb_flags & SB_RDONLY))
> -		ext4_commit_super(sb, 1);
> +	if (sbi->s_journal == NULL && !(old_sb_flags & SB_RDONLY)) {
> +		err = ext4_commit_super(sb, 1);
> +		goto restore_opts;
> +	}

Why is goto restore_opts unconditional here?

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH v3] ext4: handle errors on ext4_commit_super

[Jaegeuk Kim]

When remounting ext4 from ro to rw, currently it allows its transition,
even if ext4_commit_super() returns EIO. Even worse thing is, after that,
fs/buffer complains buffer dirty bits like:

 Call trace:
 [<ffffff9750c259dc>] mark_buffer_dirty+0x184/0x1a4
 [<ffffff9750cb398c>] __ext4_handle_dirty_super+0x4c/0xfc
 [<ffffff9750c7a9fc>] ext4_file_open+0x154/0x1c0
 [<ffffff9750bea51c>] do_dentry_open+0x114/0x2d0
 [<ffffff9750bea75c>] vfs_open+0x5c/0x94
 [<ffffff9750bf879c>] path_openat+0x668/0xfe8
 [<ffffff9750bf8088>] do_filp_open+0x74/0x120
 [<ffffff9750beac98>] do_sys_open+0x148/0x254
 [<ffffff9750beade0>] SyS_openat+0x10/0x18
 [<ffffff9750a83ab0>] el0_svc_naked+0x24/0x28
 EXT4-fs (dm-1): previous I/O error to superblock detected
 Buffer I/O error on dev dm-1, logical block 0, lost sync page write
 EXT4-fs (dm-1): re-mounted. Opts: (null)
 Buffer I/O error on dev dm-1, logical block 80, lost async page write

Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: linux-ext4@vger.kernel.org
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>
---

Change log from v2:
 - fix missing goto condition

 fs/ext4/super.c | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 185f7e61f4cf..32cf16c33cba 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2116,12 +2116,12 @@ static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
 			    int read_only)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
-	int res = 0;
+	int err = 0;
 
 	if (le32_to_cpu(es->s_rev_level) > EXT4_MAX_SUPP_REV) {
 		ext4_msg(sb, KERN_ERR, "revision level too high, "
 			 "forcing read-only mode");
-		res = SB_RDONLY;
+		err = -EROFS;
 	}
 	if (read_only)
 		goto done;
@@ -2154,7 +2154,7 @@ static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
 	if (sbi->s_journal)
 		ext4_set_feature_journal_needs_recovery(sb);
 
-	ext4_commit_super(sb, 1);
+	err = ext4_commit_super(sb, 1);
 done:
 	if (test_opt(sb, DEBUG))
 		printk(KERN_INFO "[EXT4 FS bs=%lu, gc=%u, "
@@ -2166,7 +2166,7 @@ static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
 			sbi->s_mount_opt, sbi->s_mount_opt2);
 
 	cleancache_init_fs(sb);
-	return res;
+	return err;
 }
 
 int ext4_alloc_flex_bg_array(struct super_block *sb, ext4_group_t ngroup)
@@ -4760,11 +4760,7 @@ static int ext4_commit_super(struct super_block *sb, int sync)
 		unlock_buffer(sbh);
 		error = __sync_dirty_buffer(sbh,
 			REQ_SYNC | (test_opt(sb, BARRIER) ? REQ_FUA : 0));
-		if (error)
-			return error;
-
-		error = buffer_write_io_error(sbh);
-		if (error) {
+		if (buffer_write_io_error(sbh)) {
 			ext4_msg(sb, KERN_ERR, "I/O error while writing "
 			       "superblock");
 			clear_buffer_write_io_error(sbh);
@@ -5165,8 +5161,12 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 			if (sbi->s_journal)
 				ext4_clear_journal_err(sb, es);
 			sbi->s_mount_state = le16_to_cpu(es->s_state);
-			if (!ext4_setup_super(sb, es, 0))
-				sb->s_flags &= ~SB_RDONLY;
+
+			err = ext4_setup_super(sb, es, 0);
+			if (err)
+				goto restore_opts;
+
+			sb->s_flags &= ~SB_RDONLY;
 			if (ext4_has_feature_mmp(sb))
 				if (ext4_multi_mount_protect(sb,
 						le64_to_cpu(es->s_mmp_block))) {
@@ -5190,8 +5190,11 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 	}
 
 	ext4_setup_system_zone(sb);
-	if (sbi->s_journal == NULL && !(old_sb_flags & SB_RDONLY))
-		ext4_commit_super(sb, 1);
+	if (sbi->s_journal == NULL && !(old_sb_flags & SB_RDONLY)) {
+		err = ext4_commit_super(sb, 1);
+		if (err)
+			goto restore_opts;
+	}
 
 #ifdef CONFIG_QUOTA
 	/* Release old quota file names */
-- 
2.17.0.484.g0c8726318c-goog

Re: [PATCH v3] ext4: handle errors on ext4_commit_super

[Theodore Y. Ts'o]

On Mon, Apr 23, 2018 at 08:46:26AM -0600, Jaegeuk Kim wrote:
> When remounting ext4 from ro to rw, currently it allows its transition,
> even if ext4_commit_super() returns EIO. Even worse thing is, after that,
> fs/buffer complains buffer dirty bits like:
> 
>  Call trace:
>  [<ffffff9750c259dc>] mark_buffer_dirty+0x184/0x1a4
>  [<ffffff9750cb398c>] __ext4_handle_dirty_super+0x4c/0xfc
>  [<ffffff9750c7a9fc>] ext4_file_open+0x154/0x1c0
>  [<ffffff9750bea51c>] do_dentry_open+0x114/0x2d0
>  [<ffffff9750bea75c>] vfs_open+0x5c/0x94
>  [<ffffff9750bf879c>] path_openat+0x668/0xfe8
>  [<ffffff9750bf8088>] do_filp_open+0x74/0x120
>  [<ffffff9750beac98>] do_sys_open+0x148/0x254
>  [<ffffff9750beade0>] SyS_openat+0x10/0x18
>  [<ffffff9750a83ab0>] el0_svc_naked+0x24/0x28
>  EXT4-fs (dm-1): previous I/O error to superblock detected
>  Buffer I/O error on dev dm-1, logical block 0, lost sync page write
>  EXT4-fs (dm-1): re-mounted. Opts: (null)
>  Buffer I/O error on dev dm-1, logical block 80, lost async page write
> 
> Cc: "Theodore Ts'o" <tytso@mit.edu>
> Cc: Andreas Dilger <adilger.kernel@dilger.ca>
> Cc: linux-ext4@vger.kernel.org
> Cc: Jaegeuk Kim <jaegeuk@kernel.org>
> Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>

Applied with a fix up to ext4_fill_super() when it calls
ext4_setup_super() with the changed error return semantics.

		   	    - Ted

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index aac33c155363..1388e56bb3f5 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4254,8 +4254,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		goto failed_mount4;
 	}
 
-	if (ext4_setup_super(sb, es, sb_rdonly(sb)))
+	ret = ext4_setup_super(sb, es, sb_rdonly(sb));
+	if (ret == -EROFS) {
 		sb->s_flags |= SB_RDONLY;
+		ret = 0;
+	} else if (ret)
+		goto failed_mount4a;
 
 	/* determine the minimum size of new large inodes, if present */
 	if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE &&