linux-kernel - Re: [PATCH] ext4: dax: Fix overflowing extents beyond inode size when partially writing

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Message-ID: <172476284024.635532.4541598386517901728.b4-ty@mit.edu>
Date: Tue, 27 Aug 2024 08:47:21 -0400
From: "Theodore Ts'o" <tytso@....edu>
To: adilger.kernel@...ger.ca, jack@...e.cz,
        Zhihao Cheng <chengzhihao@...weicloud.com>
Cc: "Theodore Ts'o" <tytso@....edu>, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org, chengzhihao1@...wei.com,
        yi.zhang@...wei.com
Subject: Re: [PATCH] ext4: dax: Fix overflowing extents beyond inode size when partially writing


On Fri, 09 Aug 2024 20:15:32 +0800, Zhihao Cheng wrote:
> The dax_iomap_rw() does two things in each iteration: map written blocks
> and copy user data to blocks. If the process is killed by user(See signal
> handling in dax_iomap_iter()), the copied data will be returned and added
> on inode size, which means that the length of written extents may exceed
> the inode size, then fsck will fail. An example is given as:
> 
> dd if=/dev/urandom of=file bs=4M count=1
>  dax_iomap_rw
>   iomap_iter // round 1
>    ext4_iomap_begin
>     ext4_iomap_alloc // allocate 0~2M extents(written flag)
>   dax_iomap_iter // copy 2M data
>   iomap_iter // round 2
>    iomap_iter_advance
>     iter->pos += iter->processed // iter->pos = 2M
>    ext4_iomap_begin
>     ext4_iomap_alloc // allocate 2~4M extents(written flag)
>   dax_iomap_iter
>    fatal_signal_pending
>   done = iter->pos - iocb->ki_pos // done = 2M
>  ext4_handle_inode_extension
>   ext4_update_inode_size // inode size = 2M
> 
> [...]

Applied, thanks!

[1/1] ext4: dax: Fix overflowing extents beyond inode size when partially writing
      commit: dda898d7ffe85931f9cca6d702a51f33717c501e

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