Re: [PATCH v9 08/14] xfs: refuse writes to files racing with realtime inode flag changes

[sashiko-bot@kernel.org]

> From: Christoph Hellwig <hch@lst.de>
> 
> Zoned writes need to reserve space before taking the iolock to avoid
> deadlocks with garbage collection.  But this means that the realtime inode
> flag which indicates if the file will be placed on the zoned realtime
> device or the main data device can be flipped after taking the reservation
> and before taking the write, or after deciding to go down the regular
> write path, both of which can't work.
> 
> Re-sample the realtime flag just before the actual write, and refuse the
> write if the flag changed.  Do not retry the write using the now correct
> path, as switching the flag under a write is not a normal use case, and
> trying to flip between the zoned and regular path is an inherent life
> lock as it could be switched around again the next time this check is
> performed.
> 
> Fixes: 058dd70c65ab ("xfs: implement buffered writes to zoned RT devices")
> Fixes: 2e2383405824 ("xfs: implement direct writes to zoned RT devices")
> Reported-by: Chris Mason <mason@kernel.org>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Chris Mason <mason@kernel.org>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261112214604.67875-1-mason@kernel.org?part=8