On 2/16/2026 7:28 PM, Yongpeng Yang wrote:
From: Yongpeng Yang <[email protected]>
After the device is mounted, f2fs updates on-disk metadata without
updating the block device page cache. As a result, f2fs-tools may read
stale metadata from the page cache.
For example:
mount /dev/vdb /mnt/f2fs
touch mx // ino = 4
sync
dump.f2fs -i 4 /dev/vdb
touch mx2 // ino = 5
sync
dump.f2fs -i 5 /dev/vdb // block addr is 0
Since `dump.f2fs -i 4 /dev/vdb` has already populated the metadata area
into the block device page cache, the cached pages remain resident in
memory. After creating mx2, the page cache is not updated accordingly.
Therefore, `dump.f2fs -i 5 /dev/vdb` reads stale metadata, and the
physical block address of inode 5 is incorrectly reported as 0.
This patch issues a BLKFLSBUF ioctl to the block device before reading
metadata. The kernel then invalidates the block device page cache,
ensuring that subsequent reads fetch uptodate metadata from disk.
Signed-off-by: Yongpeng Yang <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Thanks,
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