New: ext4: dax: overflowing extents beyond inode size when partially writing

https://bugzilla.kernel.org/show_bug.cgi?id=219136

Bug ID: 219136
Summary: ext4: dax: overflowing extents beyond inode size when
partially writing
Product: File System
Version: 2.5
Hardware: All
OS: Linux
Status: NEW
Severity: normal
Priority: P3
Component: ext4
Assignee: [email protected]
Reporter: [email protected]
Regression: No

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

fsck reports: Inode 13, i_size is 2097152, should be 4194304. Fix?

Reproducer:
1. Apply diff and compile kernel
2. ./test.sh
mke2fs 1.47.0 (5-Feb-2023)
Creating filesystem with 524288 4k blocks and 131072 inodes Filesystem UUID: e2c71b4e-3315-4463-8613-ea3f40bf1efb Superblock backups stored on blocks:

        32768, 98304, 163840, 229376, 294912

Allocating group tables: done
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done

./test.sh: line 18: 1559 Terminated dd if=/dev/urandom
of=$MNT/file bs=4M count=1
e2fsck 1.47.0 (5-Feb-2023)
Pass 1: Checking inodes, blocks, and sizes Inode 13, i_size is 2097152, should be 4194304. Fix? no

Pass 2: Checking directory structure Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information

/dev/pmem2: ********** WARNING: Filesystem still has errors **********

/dev/pmem2: 13/131072 files (0.0% non-contiguous), 27308/524288 blocks

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https://bugzilla.kernel.org/show_bug.cgi?id=219136

--- Comment #1 from Zhihao Cheng ([email protected]) --- Created attachment 306683
--> https://bugzilla.kernel.org/attachment.cgi?id=306683&action=edit
diff

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https://bugzilla.kernel.org/show_bug.cgi?id=219136

--- Comment #2 from Zhihao Cheng ([email protected]) --- Created attachment 306684
--> https://bugzilla.kernel.org/attachment.cgi?id=306684&action=edit
test.sh

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