Re: [PATCH] block: fix BLKSECDISCARD zero-length range causing page cache invalidation

[Christoph Hellwig]

On Sat, Jul 04, 2026 at 03:39:42PM +0800, Zizhi Wo wrote:
> From: Zizhi Wo <wozizhi@xxxxxxxxxx>
> 
> Commit 697ba0b6ec4a ("block: fix integer overflow in BLKSECDISCARD") fixed
> the start+len overflow via check_add_overflow() but did not handle the
> start=0, len=0 case. There, start + len = 0, so end = 0 passes all checks,
> and truncate_bdev_range()->truncate_inode_pages_range() is then called with
> lend=UINT64_MAX, whitch is the "truncate to the end of file" sentinel, so
> the entire page cache is invalidated.
> 
> Fix this by replacing the validation with blk_validate_byte_range(), which
> already rejects a zero-length range and is what BLKDISCARD uses. This also
> switches the alignment check from a hardcoded 512 to
> bdev_logical_block_size().

I though I had reviewed this before?  But either way it looks good:

Reviewed-by: Christoph Hellwig <hch@xxxxxx>