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Message-ID: <da12e81d-cf29-6dd3-b01e-2319aa9487d5@oracle.com>
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
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