linux-kernel - Re: [PATCH 03/21] fs/bdev: Add atomic write support info to statx

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 3 Oct 2023 08:23:26 +0100
From:   John Garry <john.g.garry@...cle.com>
To:     "Darrick J. Wong" <djwong@...nel.org>,
        Dave Chinner <david@...morbit.com>
Cc:     Bart Van Assche <bvanassche@....org>,
        Eric Biggers <ebiggers@...nel.org>, axboe@...nel.dk,
        kbusch@...nel.org, hch@....de, sagi@...mberg.me,
        jejb@...ux.ibm.com, martin.petersen@...cle.com,
        viro@...iv.linux.org.uk, brauner@...nel.org,
        chandan.babu@...cle.com, dchinner@...hat.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, tytso@....edu, jbongio@...gle.com,
        linux-api@...r.kernel.org,
        Prasad Singamsetty <prasad.singamsetty@...cle.com>
Subject: Re: [PATCH 03/21] fs/bdev: Add atomic write support info to statx

On 03/10/2023 03:57, Darrick J. Wong wrote:
>>>>> +#define STATX_ATTR_WRITE_ATOMIC        0x00400000 /* File
>>>>> supports atomic write operations */
>>>> How would this differ from stx_atomic_write_unit_min != 0?
>> Yeah, I suppose that we can just not set this for the case of
>> stx_atomic_write_unit_min == 0.
> Please use the STATX_ATTR_WRITE_ATOMIC flag to indicate that the
> filesystem, file and underlying device support atomic writes when
> the values are non-zero. The whole point of the attribute mask is
> that the caller can check the mask for supported functionality
> without having to read every field in the statx structure to
> determine if the functionality it wants is present.

Sure, but again that would be just checking atomic_write_unit_min_bytes 
or another atomic write block setting as that is the only way to tell 
from the block layer (if atomic writes are supported), so it will be 
something like:

if (request_mask & STATX_WRITE_ATOMIC && 
queue_atomic_write_unit_min_bytes(bdev->bd_queue)) {
     stat->atomic_write_unit_min =
       queue_atomic_write_unit_min_bytes(bdev->bd_queue);
     stat->atomic_write_unit_max =
       queue_atomic_write_unit_max_bytes(bdev->bd_queue);
     stat->attributes |= STATX_ATTR_WRITE_ATOMIC;
     stat->attributes_mask |= STATX_ATTR_WRITE_ATOMIC;
     stat->result_mask |= STATX_WRITE_ATOMIC;
}

Thanks,
John