linux-kernel - Re: [RFC PATCH v4 07/11] fs: statx add write zeroes unmap attribute

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Message-ID: <c7d8d0c3-7efa-4ee6-b518-f8b09ec87b73@huaweicloud.com>
Date: Tue, 6 May 2025 12:28:54 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: "Darrick J. Wong" <djwong@...nel.org>, Christoph Hellwig <hch@....de>
Cc: linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
 linux-block@...r.kernel.org, dm-devel@...ts.linux.dev,
 linux-nvme@...ts.infradead.org, linux-scsi@...r.kernel.org,
 linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org, tytso@....edu,
 john.g.garry@...cle.com, bmarzins@...hat.com, chaitanyak@...dia.com,
 shinichiro.kawasaki@....com, brauner@...nel.org, yi.zhang@...wei.com,
 chengzhihao1@...wei.com, yukuai3@...wei.com, yangerkun@...wei.com
Subject: Re: [RFC PATCH v4 07/11] fs: statx add write zeroes unmap attribute

On 2025/5/5 22:29, Darrick J. Wong wrote:
> On Mon, May 05, 2025 at 03:22:08PM +0200, Christoph Hellwig wrote:
>> On Mon, Apr 21, 2025 at 10:15:05AM +0800, Zhang Yi wrote:
>>> From: Zhang Yi <yi.zhang@...wei.com>
>>>
>>> Add a new attribute flag to statx to determine whether a bdev or a file
>>> supports the unmap write zeroes command.
>>>
>>> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
>>> ---
>>>  block/bdev.c              | 4 ++++
>>>  fs/ext4/inode.c           | 9 ++++++---
>>>  include/uapi/linux/stat.h | 1 +
>>>  3 files changed, 11 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/block/bdev.c b/block/bdev.c
>>> index 4844d1e27b6f..29b0e5feb138 100644
>>> --- a/block/bdev.c
>>> +++ b/block/bdev.c
>>> @@ -1304,6 +1304,10 @@ void bdev_statx(struct path *path, struct kstat *stat,
>>>  			queue_atomic_write_unit_max_bytes(bd_queue));
>>>  	}
>>>  
>>> +	if (bdev_write_zeroes_unmap(bdev))
>>> +		stat->attributes |= STATX_ATTR_WRITE_ZEROES_UNMAP;
>>> +	stat->attributes_mask |= STATX_ATTR_WRITE_ZEROES_UNMAP;
>>
>> Hmm, shouldn't this always be set by stat?  But I might just be
>> really confused what attributes_mask is, and might in fact have
>> misapplied it in past patches of my own..
> 
> attributes_mask contains attribute flags known to the filesystem,
> whereas attributes contains flags actually set on the file.
> "known_attributes" would have been a better name, but that's water under
> the bridge. :P
> 
>> Also shouldn't the patches to report the flag go into the bdev/ext4
>> patches that actually implement the feature for the respective files
>> to keep bisectability?
> 
> /I/ think so...
> 

OK, since this statx reporting flag is not strongly tied to
FALLOC_FL_WRITE_ZEROES in vfs_fallocate(), I'll split this patch into
three separate patches.

Thanks,
Yi.