linux-kernel - Re: [PATCH 2/6] ext4: Check for atomic writes support in write iter

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Message-ID: <87msism5rg.fsf@gmail.com>
Date: Fri, 25 Oct 2024 23:20:11 +0530
From: Ritesh Harjani (IBM) <ritesh.list@...il.com>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: John Garry <john.g.garry@...cle.com>, linux-ext4@...r.kernel.org, Theodore Ts'o <tytso@....edu>, Jan Kara <jack@...e.cz>, Christoph Hellwig <hch@...radead.org>, Ojaswin Mujoo <ojaswin@...ux.ibm.com>, Dave Chinner <david@...morbit.com>, linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 2/6] ext4: Check for atomic writes support in write iter

"Darrick J. Wong" <djwong@...nel.org> writes:

> On Fri, Oct 25, 2024 at 04:03:02PM +0530, Ritesh Harjani wrote:
>> John Garry <john.g.garry@...cle.com> writes:
>> 
>> > On 25/10/2024 04:45, Ritesh Harjani (IBM) wrote:
>> >> Let's validate using generic_atomic_write_valid() in
>> >> ext4_file_write_iter() if the write request has IOCB_ATOMIC set.
>> >> 
>> >> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
>> >> ---
>> >>   fs/ext4/file.c | 14 ++++++++++++++
>> >>   1 file changed, 14 insertions(+)
>> >> 
>> >> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
>> >> index f14aed14b9cf..b06c5d34bbd2 100644
>> >> --- a/fs/ext4/file.c
>> >> +++ b/fs/ext4/file.c
>> >> @@ -692,6 +692,20 @@ ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
>> >>   	if (IS_DAX(inode))
>> >>   		return ext4_dax_write_iter(iocb, from);
>> >>   #endif
>> >> +
>> >> +	if (iocb->ki_flags & IOCB_ATOMIC) {
>> >> +		size_t len = iov_iter_count(from);
>> >> +		int ret;
>> >> +
>> >> +		if (!IS_ALIGNED(len, EXT4_SB(inode->i_sb)->fs_awu_min) ||
>> >> +			len > EXT4_SB(inode->i_sb)->fs_awu_max)
>> >> +			return -EINVAL;
>> >
>> > this looks ok, but the IS_ALIGNED() check looks odd. I am not sure why 
>> > you don't just check that fs_awu_max >= len >= fs_awu_min
>> >
>> 
>> I guess this was just a stricter check. But we anyways have power_of_2
>> and other checks in generic_atomic_write_valid(). So it does not matter. 
>> 
>> I can change this in v2. 
>
> Also please fix the weird indenting in the if test:
>
> 		if (len < EXT4_SB(inode->i_sb)->fs_awu_min) ||
> 		    len > EXT4_SB(inode->i_sb)->fs_awu_max)
> 			return -EINVAL;
>
> --D

Got it!

-ritesh

>
>> Thanks!
>> 
>> >> +
>> >> +		ret = generic_atomic_write_valid(iocb, from);
>> >> +		if (ret)
>> >> +			return ret;
>> >> +	}
>> >> +
>> >>   	if (iocb->ki_flags & IOCB_DIRECT)
>> >>   		return ext4_dio_write_iter(iocb, from);
>> >>   	else
>> 
>> -ritesh
>>