Re: [PATCH] ntfs: fix lost volume flag updates in set/clear helpers

[liubaolin <liubaolin12138@163.com>]

在 2026/9/1 10:45, Hongling Zeng 写道:
> ntfs_set_volume_flags() and ntfs_clear_volume_flags() both read
> vol->vol_flags outside any lock to compute the new value before handing
> it to ntfs_write_volume_flags(), which only takes ni->mrec_lock around
> the actual write. The read-modify-write is therefore not atomic, and two
> concurrent callers can lose an update: ntfs_sync_fs() may derive a
> "clean" value from vol->vol_flags while a writer concurrently records an
> error and sets VOLUME_IS_DIRTY; the locked write then silently
> overwrites the freshly-set dirty bit. The on-disk volume looks clean
> despite the recorded errors, so chkdsk will not run on the next mount
> and corrupted metadata can persist.
> 
> Fix by moving the read-modify-write inside the mrec_lock: pass the bits
> to set and to clear separately, and combine them with the current flag
> state under the lock inside ntfs_write_volume_flags(). The set/clear
> helpers pass only the bits to modify, not the complete flag state. The
> bit manipulation is done on CPU-endian values, and the result is
> converted back to little-endian before storing it. The wrappers keep
> their signatures so callers are unchanged.

Looks good to me.

Reviewed-by: Baolin Liu <liubaolin@kylinos.cn>