[PATCH] ext4: Avoid entering writeback paths during fastcommit replay

[PATCH] ext4: Avoid entering writeback paths during fastcommit replay

[Jan Kara]

Fastcommit replay effectively happens in nojournal mode. This results in
ext4_mark_iloc_dirty() setting I_METADATA_WRITEBACK flag and as a result
we end up entering filesystem writeback functions. However during
fastcommit replay s_writepages_rwsem isn't initialized yet and hence we
crash.

Fix the problem by avoiding setting I_METADATA_WRITEBACK during
fastcommit replay. Journal replay flushes the whole block device after
replay anyway so all metadata is properly persisted and replay is faster
this way as a bonus.

Fixes: c26339e1df33 ("ext4: Fix data integrity writeout issues in nojournal mode")
Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Reported-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/inode.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

Christian, please add this fixup to my sync fixing series. Thanks!

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 7a1f961cd11c..12ff84ab5741 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -6408,9 +6408,10 @@ int ext4_chunk_trans_blocks(struct inode *inode, int nrblocks)
 int ext4_mark_iloc_dirty(handle_t *handle,
 			 struct inode *inode, struct ext4_iloc *iloc)
 {
+	struct super_block *sb = inode->i_sb;
 	int err = 0;
 
-	err = ext4_emergency_state(inode->i_sb);
+	err = ext4_emergency_state(sb);
 	if (unlikely(err)) {
 		put_bh(iloc->bh);
 		return err;
@@ -6425,9 +6426,13 @@ int ext4_mark_iloc_dirty(handle_t *handle,
 	put_bh(iloc->bh);
 	/*
 	 * Mark that there's metadata writeout pending for the inode so that it
-	 * gets properly flushed on fsync(2) and similar.
+	 * gets properly flushed on fsync(2) and similar. We don't bother for
+	 * fastcommit replay as that flushes the whole bdev afterwards anyway.
+	 * It is faster this way and we avoid entering fs writeback paths which
+	 * aren't fully initialized yet.
 	 */
-	if (!EXT4_SB(inode->i_sb)->s_journal) {
+	if (!ext4_handle_valid(handle) &&
+	    !(EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY)) {
 		/*
 		 * Inode didn't need to go through dirtying, make sure it is
 		 * attached to wb so that writeback can handle it.
-- 
2.51.0

Re: [PATCH] ext4: Avoid entering writeback paths during fastcommit replay

[Ojaswin Mujoo]

On Tue, Aug 04, 2026 at 12:41:13PM +0200, Jan Kara wrote:
> Fastcommit replay effectively happens in nojournal mode. This results in
> ext4_mark_iloc_dirty() setting I_METADATA_WRITEBACK flag and as a result
> we end up entering filesystem writeback functions. However during
> fastcommit replay s_writepages_rwsem isn't initialized yet and hence we
> crash.
> 
> Fix the problem by avoiding setting I_METADATA_WRITEBACK during
> fastcommit replay. Journal replay flushes the whole block device after
> replay anyway so all metadata is properly persisted and replay is faster
> this way as a bonus.
> 
> Fixes: c26339e1df33 ("ext4: Fix data integrity writeout issues in nojournal mode")
> Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
> Reported-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---

Hey Jan, yes makese sense and it is fixing the issue for me. Feel free
to add:

Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>

Regards,
ojaswin


>  fs/ext4/inode.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> Christian, please add this fixup to my sync fixing series. Thanks!
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 7a1f961cd11c..12ff84ab5741 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -6408,9 +6408,10 @@ int ext4_chunk_trans_blocks(struct inode *inode, int nrblocks)
>  int ext4_mark_iloc_dirty(handle_t *handle,
>  			 struct inode *inode, struct ext4_iloc *iloc)
>  {
> +	struct super_block *sb = inode->i_sb;
>  	int err = 0;
>  
> -	err = ext4_emergency_state(inode->i_sb);
> +	err = ext4_emergency_state(sb);
>  	if (unlikely(err)) {
>  		put_bh(iloc->bh);
>  		return err;
> @@ -6425,9 +6426,13 @@ int ext4_mark_iloc_dirty(handle_t *handle,
>  	put_bh(iloc->bh);
>  	/*
>  	 * Mark that there's metadata writeout pending for the inode so that it
> -	 * gets properly flushed on fsync(2) and similar.
> +	 * gets properly flushed on fsync(2) and similar. We don't bother for
> +	 * fastcommit replay as that flushes the whole bdev afterwards anyway.
> +	 * It is faster this way and we avoid entering fs writeback paths which
> +	 * aren't fully initialized yet.
>  	 */
> -	if (!EXT4_SB(inode->i_sb)->s_journal) {
> +	if (!ext4_handle_valid(handle) &&
> +	    !(EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY)) {
>  		/*
>  		 * Inode didn't need to go through dirtying, make sure it is
>  		 * attached to wb so that writeback can handle it.
> -- 
> 2.51.0
> 

Re: [PATCH] ext4: Avoid entering writeback paths during fastcommit replay

[Theodore Tso]

On Tue, Aug 04, 2026 at 12:41:13PM -0500, Jan Kara wrote:
> Fastcommit replay effectively happens in nojournal mode. This results in
> ext4_mark_iloc_dirty() setting I_METADATA_WRITEBACK flag and as a result
> we end up entering filesystem writeback functions. However during
> fastcommit replay s_writepages_rwsem isn't initialized yet and hence we
> crash.
> 
> Fix the problem by avoiding setting I_METADATA_WRITEBACK during
> fastcommit replay. Journal replay flushes the whole block device after
> replay anyway so all metadata is properly persisted and replay is faster

It looks like this patch is only applicable if the patch series "fs:
Fix missed inode write during fsync" is applied, and in fact appears
to fix a problem introduced in "[PATCH v5 17/20] ext4: Fix data
integrity writeout issues in nojournal mode"?

						- Ted

Re: [PATCH] ext4: Avoid entering writeback paths during fastcommit replay

[Jan Kara]

On Thu 06-08-26 10:48:47, Theodore Tso wrote:
> On Tue, Aug 04, 2026 at 12:41:13PM -0500, Jan Kara wrote:
> > Fastcommit replay effectively happens in nojournal mode. This results in
> > ext4_mark_iloc_dirty() setting I_METADATA_WRITEBACK flag and as a result
> > we end up entering filesystem writeback functions. However during
> > fastcommit replay s_writepages_rwsem isn't initialized yet and hence we
> > crash.
> > 
> > Fix the problem by avoiding setting I_METADATA_WRITEBACK during
> > fastcommit replay. Journal replay flushes the whole block device after
> > replay anyway so all metadata is properly persisted and replay is faster
> 
> It looks like this patch is only applicable if the patch series "fs:
> Fix missed inode write during fsync" is applied, and in fact appears
> to fix a problem introduced in "[PATCH v5 17/20] ext4: Fix data
> integrity writeout issues in nojournal mode"?

Right, yes, it's meant for Christian to pick this patch up to his tree.

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

Re: [PATCH] ext4: Avoid entering writeback paths during fastcommit replay

[Venkat Rao Bagalkote]

On 04/08/26 4:11 pm, Jan Kara wrote:
> Fastcommit replay effectively happens in nojournal mode. This results in
> ext4_mark_iloc_dirty() setting I_METADATA_WRITEBACK flag and as a result
> we end up entering filesystem writeback functions. However during
> fastcommit replay s_writepages_rwsem isn't initialized yet and hence we
> crash.
>
> Fix the problem by avoiding setting I_METADATA_WRITEBACK during
> fastcommit replay. Journal replay flushes the whole block device after
> replay anyway so all metadata is properly persisted and replay is faster
> this way as a bonus.
>
> Fixes: c26339e1df33 ("ext4: Fix data integrity writeout issues in nojournal mode")
> Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
> Reported-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---


Tested this patch and its fixes the reported issue. Hence,

Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>


Regards,

Venkat.


>   fs/ext4/inode.c | 11 ++++++++---
>   1 file changed, 8 insertions(+), 3 deletions(-)
>
> Christian, please add this fixup to my sync fixing series. Thanks!
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 7a1f961cd11c..12ff84ab5741 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -6408,9 +6408,10 @@ int ext4_chunk_trans_blocks(struct inode *inode, int nrblocks)
>   int ext4_mark_iloc_dirty(handle_t *handle,
>   			 struct inode *inode, struct ext4_iloc *iloc)
>   {
> +	struct super_block *sb = inode->i_sb;
>   	int err = 0;
>   
> -	err = ext4_emergency_state(inode->i_sb);
> +	err = ext4_emergency_state(sb);
>   	if (unlikely(err)) {
>   		put_bh(iloc->bh);
>   		return err;
> @@ -6425,9 +6426,13 @@ int ext4_mark_iloc_dirty(handle_t *handle,
>   	put_bh(iloc->bh);
>   	/*
>   	 * Mark that there's metadata writeout pending for the inode so that it
> -	 * gets properly flushed on fsync(2) and similar.
> +	 * gets properly flushed on fsync(2) and similar. We don't bother for
> +	 * fastcommit replay as that flushes the whole bdev afterwards anyway.
> +	 * It is faster this way and we avoid entering fs writeback paths which
> +	 * aren't fully initialized yet.
>   	 */
> -	if (!EXT4_SB(inode->i_sb)->s_journal) {
> +	if (!ext4_handle_valid(handle) &&
> +	    !(EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY)) {
>   		/*
>   		 * Inode didn't need to go through dirtying, make sure it is
>   		 * attached to wb so that writeback can handle it.

Re: [PATCH] ext4: Avoid entering writeback paths during fastcommit replay

[Jan Kara]

Hello Christian!

With all the vacations going on this fixup to apply on top of vfs-7.3.sync
branch seems to have fallen through the cracks (I guess the note below the
changelog was too hidden, next time I'll try to indicate this is a fixup
inside the subject - maybe like [PATCH FIXUP vfs-7.3.sync]). Anyway, can
you please pick it up and push it to Linus later during the merge window?
Thanks!

								Honza

On Tue 04-08-26 12:41:13, Jan Kara wrote:
> Fastcommit replay effectively happens in nojournal mode. This results in
> ext4_mark_iloc_dirty() setting I_METADATA_WRITEBACK flag and as a result
> we end up entering filesystem writeback functions. However during
> fastcommit replay s_writepages_rwsem isn't initialized yet and hence we
> crash.
> 
> Fix the problem by avoiding setting I_METADATA_WRITEBACK during
> fastcommit replay. Journal replay flushes the whole block device after
> replay anyway so all metadata is properly persisted and replay is faster
> this way as a bonus.
> 
> Fixes: c26339e1df33 ("ext4: Fix data integrity writeout issues in nojournal mode")
> Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
> Reported-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  fs/ext4/inode.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> Christian, please add this fixup to my sync fixing series. Thanks!
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 7a1f961cd11c..12ff84ab5741 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -6408,9 +6408,10 @@ int ext4_chunk_trans_blocks(struct inode *inode, int nrblocks)
>  int ext4_mark_iloc_dirty(handle_t *handle,
>  			 struct inode *inode, struct ext4_iloc *iloc)
>  {
> +	struct super_block *sb = inode->i_sb;
>  	int err = 0;
>  
> -	err = ext4_emergency_state(inode->i_sb);
> +	err = ext4_emergency_state(sb);
>  	if (unlikely(err)) {
>  		put_bh(iloc->bh);
>  		return err;
> @@ -6425,9 +6426,13 @@ int ext4_mark_iloc_dirty(handle_t *handle,
>  	put_bh(iloc->bh);
>  	/*
>  	 * Mark that there's metadata writeout pending for the inode so that it
> -	 * gets properly flushed on fsync(2) and similar.
> +	 * gets properly flushed on fsync(2) and similar. We don't bother for
> +	 * fastcommit replay as that flushes the whole bdev afterwards anyway.
> +	 * It is faster this way and we avoid entering fs writeback paths which
> +	 * aren't fully initialized yet.
>  	 */
> -	if (!EXT4_SB(inode->i_sb)->s_journal) {
> +	if (!ext4_handle_valid(handle) &&
> +	    !(EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY)) {
>  		/*
>  		 * Inode didn't need to go through dirtying, make sure it is
>  		 * attached to wb so that writeback can handle it.
> -- 
> 2.51.0
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH] ext4: Avoid entering writeback paths during fastcommit replay

[Christian Brauner]

On Mon, Aug 17, 2026 at 03:55:31PM +0200, Jan Kara wrote:
> Hello Christian!
> 
> With all the vacations going on this fixup to apply on top of vfs-7.3.sync
> branch seems to have fallen through the cracks (I guess the note below the
> changelog was too hidden, next time I'll try to indicate this is a fixup
> inside the subject - maybe like [PATCH FIXUP vfs-7.3.sync]). Anyway, can
> you please pick it up and push it to Linus later during the merge window?
> Thanks!

Yes, sorrry I missed this! Picked it up now. Thanks for reminding me!

Christian

Re: [PATCH] ext4: Avoid entering writeback paths during fastcommit replay

[Christian Brauner]

On Tue, 04 Aug 2026 12:41:13 +0200, Jan Kara wrote:
> Fastcommit replay effectively happens in nojournal mode. This results in
> ext4_mark_iloc_dirty() setting I_METADATA_WRITEBACK flag and as a result
> we end up entering filesystem writeback functions. However during
> fastcommit replay s_writepages_rwsem isn't initialized yet and hence we
> crash.
> 
> Fix the problem by avoiding setting I_METADATA_WRITEBACK during
> fastcommit replay. Journal replay flushes the whole block device after
> replay anyway so all metadata is properly persisted and replay is faster
> this way as a bonus.
> 
> [...]

Applied to the vfs.fixes branch of the vfs/vfs.git tree.
Patches in the vfs.fixes branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.fixes

[1/1] ext4: Avoid entering writeback paths during fastcommit replay
      https://git.kernel.org/vfs/vfs/c/0ecd56573c1f