[PATCH 1/2] ext4: Fixes len calculation in mpage_journal_page_buffers

[PATCH 1/2] ext4: Fixes len calculation in mpage_journal_page_buffers

[Ritesh Harjani (IBM)]

Truncate operation can race with writeback, in which inode->i_size can get
truncated and therefore size - folio_pos() can be negative. This fixes the
len calculation. However this path doesn't get easily triggered even
with data journaling.

Cc:  <stable@kernel.org> # v6.5
Fixes: 80be8c5cc925 ("Fixes: ext4: Make mpage_journal_page_buffers use folio")
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 fs/ext4/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 537803250ca9..bab9223d94ac 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2334,7 +2334,7 @@ static int mpage_journal_page_buffers(handle_t *handle,
 
 	if (folio_pos(folio) + len > size &&
 	    !ext4_verity_in_progress(inode))
-		len = size - folio_pos(folio);
+		len = size & (len - 1);
 
 	return ext4_journal_folio_buffers(handle, folio, len);
 }
-- 
2.39.2

[PATCH 2/2] ext4: Remove PAGE_MASK dependency on mpage_submit_folio

[Ritesh Harjani (IBM)]

This patch simply removes the PAGE_MASK dependency since
mpage_submit_folio() is already converted to work with folio.

Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 fs/ext4/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index bab9223d94ac..e8b0773e5d2d 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1865,7 +1865,7 @@ static int mpage_submit_folio(struct mpage_da_data *mpd, struct folio *folio)
 	len = folio_size(folio);
 	if (folio_pos(folio) + len > size &&
 	    !ext4_verity_in_progress(mpd->inode))
-		len = size & ~PAGE_MASK;
+		len = size & (len - 1);
 	err = ext4_bio_write_folio(&mpd->io_submit, folio, len);
 	if (!err)
 		mpd->wbc->nr_to_write--;
-- 
2.39.2

Re: [PATCH 2/2] ext4: Remove PAGE_MASK dependency on mpage_submit_folio

[Jan Kara]

On Thu 29-02-24 11:40:14, Ritesh Harjani (IBM) wrote:
> This patch simply removes the PAGE_MASK dependency since
> mpage_submit_folio() is already converted to work with folio.
> 
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/ext4/inode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index bab9223d94ac..e8b0773e5d2d 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1865,7 +1865,7 @@ static int mpage_submit_folio(struct mpage_da_data *mpd, struct folio *folio)
>  	len = folio_size(folio);
>  	if (folio_pos(folio) + len > size &&
>  	    !ext4_verity_in_progress(mpd->inode))
> -		len = size & ~PAGE_MASK;
> +		len = size & (len - 1);
>  	err = ext4_bio_write_folio(&mpd->io_submit, folio, len);
>  	if (!err)
>  		mpd->wbc->nr_to_write--;
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH 1/2] ext4: Fixes len calculation in mpage_journal_page_buffers

[Jan Kara]

On Thu 29-02-24 11:40:13, Ritesh Harjani (IBM) wrote:
> Truncate operation can race with writeback, in which inode->i_size can get
> truncated and therefore size - folio_pos() can be negative. This fixes the
> len calculation. However this path doesn't get easily triggered even
> with data journaling.
> 
> Cc:  <stable@kernel.org> # v6.5
> Fixes: 80be8c5cc925 ("Fixes: ext4: Make mpage_journal_page_buffers use folio")
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/ext4/inode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 537803250ca9..bab9223d94ac 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -2334,7 +2334,7 @@ static int mpage_journal_page_buffers(handle_t *handle,
>  
>  	if (folio_pos(folio) + len > size &&
>  	    !ext4_verity_in_progress(inode))
> -		len = size - folio_pos(folio);
> +		len = size & (len - 1);
>  
>  	return ext4_journal_folio_buffers(handle, folio, len);
>  }
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH 1/2] ext4: Fixes len calculation in mpage_journal_page_buffers

[Theodore Ts'o]

On Thu, 29 Feb 2024 11:40:13 +0530, Ritesh Harjani (IBM) wrote:
> Truncate operation can race with writeback, in which inode->i_size can get
> truncated and therefore size - folio_pos() can be negative. This fixes the
> len calculation. However this path doesn't get easily triggered even
> with data journaling.
> 
> 

Applied, thanks!

[1/2] ext4: Fixes len calculation in mpage_journal_page_buffers
      commit: c2a09f3d782de952f09a3962d03b939e7fa7ffa4
[2/2] ext4: Remove PAGE_MASK dependency on mpage_submit_folio
      commit: 53c17fe55a06cbb405b94d96759611d725d2c47a

Best regards,
-- 
Theodore Ts'o <tytso@mit.edu>