linux-kernel - Re: [PATCH] xfs: clean code for setting bma length in xfs_bmapi

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Date:   Sun, 13 Dec 2020 00:12:53 +0800
From:   Gao Xiang <hsiangkao@...hat.com>
To:     chenlei0x@...il.com
Cc:     darrick.wong@...cle.com, linux-xfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, Lei Chen <lennychen@...cent.com>
Subject: Re: [PATCH] xfs: clean code for setting bma length in xfs_bmapi_write

On Sat, Dec 12, 2020 at 08:48:17PM +0800, chenlei0x@...il.com wrote:
> From: Lei Chen <lennychen@...cent.com>
> 
> xfs_bmapi_write may need alloc blocks when it encounters a hole
> or delay extent. When setting bma.length, it does not need comparing
> MAXEXTLEN and the length that the caller wants, because
> xfs_bmapi_allocate will handle every thing properly for bma.length.
> 
> Signed-off-by: Lei Chen <lennychen@...cent.com>
> ---
>  fs/xfs/libxfs/xfs_bmap.c | 13 +------------
>  1 file changed, 1 insertion(+), 12 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index dcf56bc..e1b6ac6 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -4417,18 +4417,7 @@ struct xfs_iread_state {
>  			bma.wasdel = wasdelay;
>  			bma.offset = bno;
>  			bma.flags = flags;
> -
> -			/*
> -			 * There's a 32/64 bit type mismatch between the
> -			 * allocation length request (which can be 64 bits in
> -			 * length) and the bma length request, which is
> -			 * xfs_extlen_t and therefore 32 bits. Hence we have to
> -			 * check for 32-bit overflows and handle them here.
> -			 */
> -			if (len > (xfs_filblks_t)MAXEXTLEN)
> -				bma.length = MAXEXTLEN;
> -			else
> -				bma.length = len;
> +			bma.length = len;

After refering to the definition of struct xfs_bmalloca, so I think
bma.length is still a xfs_extlen_t ===> uint32_t, so I'm afraid the commit
a99ebf43f49f ("xfs: fix allocation length overflow in xfs_bmapi_write()")

and the reason for adding this is still valid for now?

Thanks,
Gao Xiang