From: John Garry <john.g.garry@oracle.com>
To: Nilay Shroff <nilay@linux.ibm.com>
Cc: axboe@kernel.dk, brauner@kernel.org, bvanassche@acm.org,
dchinner@redhat.com, djwong@kernel.org, hch@lst.de, jack@suse.cz,
jbongio@google.com, jejb@linux.ibm.com, kbusch@kernel.org,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
linux-scsi@vger.kernel.org, linux-xfs@vger.kernel.org,
martin.petersen@oracle.com, ming.lei@redhat.com,
ojaswin@linux.ibm.com, sagi@grimberg.me, tytso@mit.edu,
viro@zeniv.linux.org.uk
Subject: Re: [PATCH v3 09/15] block: Add checks to merging of atomic writes
Date: Mon, 12 Feb 2024 11:20:48 +0000 [thread overview]
Message-ID: <484a449b-5c7e-4766-97d3-36b01c78687c@oracle.com> (raw)
In-Reply-To: <20240212105444.43262-1-nilay@linux.ibm.com>
>> +
>
>> + imask = ~mask;
>
>> +
>
>> + /* Top bits are different, so crossed a boundary */
>
>> + if ((start & imask) != (end & imask))
>
>> + return true;
>
>> +
>
>> + return false;
>
>> +}
>
>> +
>
I'm not sure what is going on with your mail client here.
>
>
> Shall we ensure here that we don't cross max limit of atomic write supported by
>
> device? It seems that if the boundary size is not advertized by the device
>
> (in fact, I have one NVMe drive which has boundary size zero i.e. nabo/nabspf/
>
> nawupf are all zero but awupf is non-zero) then we (unconditionally) allow
>
> merging. However it may be possible that post merging the total size of the
>
> request may exceed the atomic-write-unit-max-size supported by the device and
>
> if that happens then most probably we would be able to catch it very late in
>
> the driver code (if the device is NVMe).
>
>
>
> So is it a good idea to validate here whether we could potentially exceed
>
> the atomic-write-max-unit-size supported by device before we allow merging?
Note that we have atomic_write_max_bytes and atomic_write_max_unit_size,
and they are not always the same thing.
>
> In case we exceed the atomic-write-max-unit-size post merge then don't allow
>
> merging?
We check this elsewhere. I just expanded the normal check for max
request size to cover atomic writes.
Normally we check that a merged request would not exceed max_sectors
value, and this max_sectors value can be got from
blk_queue_get_max_sectors().
So if you check a function like ll_back_merge_fn(), we have a merging
size check:
if (blk_rq_sectors(req) + bio_sectors(bio) >
blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
req_set_nomerge(req->q, req);
return 0;
}
And here the blk_rq_get_max_sectors() -> blk_queue_get_max_sectors()
call now also supports atomic writes (see patch #7):
@@ -167,7 +167,16 @@ static inline unsigned get_max_io_size(struct bio *bio,
{
...
+ if (bio->bi_opf & REQ_ATOMIC)
+ max_sectors = lim->atomic_write_max_sectors;
+ else
+ max_sectors = lim->max_sectors;
Note that we do not allow merging of atomic and non-atomic writes.
Thanks,
John
next prev parent reply other threads:[~2024-02-12 11:21 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-24 11:38 [PATCH v3 00/15] block atomic writes John Garry
2024-01-24 11:38 ` [PATCH v3 01/15] block: Add atomic write operations to request_queue limits John Garry
2024-02-13 6:22 ` Christoph Hellwig
2024-01-24 11:38 ` [PATCH v3 02/15] block: Limit atomic writes according to bio and queue limits John Garry
2024-02-13 4:33 ` Ritesh Harjani
2024-02-13 8:05 ` John Garry
2024-01-24 11:38 ` [PATCH v3 03/15] fs/bdev: Add atomic write support info to statx John Garry
2024-01-24 11:38 ` [PATCH v3 04/15] fs: Add RWF_ATOMIC and IOCB_ATOMIC flags for atomic write support John Garry
2024-01-24 11:38 ` [PATCH v3 05/15] block: Add REQ_ATOMIC flag John Garry
2024-02-13 6:24 ` Christoph Hellwig
2024-01-24 11:38 ` [PATCH v3 06/15] block: Pass blk_queue_get_max_sectors() a request pointer John Garry
2024-02-13 6:23 ` Christoph Hellwig
2024-02-13 8:15 ` John Garry
2024-01-24 11:38 ` [PATCH v3 07/15] block: Limit atomic write IO size according to atomic_write_max_sectors John Garry
2024-02-13 6:26 ` Christoph Hellwig
2024-02-13 8:15 ` John Garry
2024-02-14 7:26 ` Christoph Hellwig
2024-02-14 9:24 ` John Garry
2024-01-24 11:38 ` [PATCH v3 08/15] block: Error an attempt to split an atomic write bio John Garry
2024-01-24 11:38 ` [PATCH v3 09/15] block: Add checks to merging of atomic writes John Garry
2024-02-12 10:54 ` Nilay Shroff
2024-02-12 11:20 ` John Garry [this message]
2024-02-12 12:01 ` [PATCH " Nilay Shroff
2024-02-12 12:09 ` John Garry
2024-02-13 6:52 ` Nilay Shroff
2024-01-24 11:38 ` [PATCH v3 10/15] block: Add fops atomic write support John Garry
2024-02-13 9:36 ` Nilay Shroff
2024-02-13 9:58 ` [PATCH " John Garry
2024-02-13 11:08 ` Nilay Shroff
2024-02-13 11:52 ` John Garry
2024-02-14 9:38 ` Nilay Shroff
2024-02-14 11:29 ` John Garry
2024-02-14 11:47 ` Nilay Shroff
2024-01-24 11:38 ` [PATCH v3 11/15] scsi: sd: Support reading atomic write properties from block limits VPD John Garry
2024-02-13 6:31 ` Christoph Hellwig
2024-02-13 8:16 ` John Garry
2024-01-24 11:38 ` [PATCH v3 12/15] scsi: sd: Add WRITE_ATOMIC_16 support John Garry
2024-01-24 11:38 ` [PATCH v3 13/15] scsi: scsi_debug: Atomic write support John Garry
2024-01-24 11:38 ` [PATCH v3 14/15] nvme: Support atomic writes John Garry
2024-02-13 6:42 ` Christoph Hellwig
2024-02-13 14:21 ` John Garry
2024-02-14 8:00 ` Christoph Hellwig
2024-02-14 9:21 ` John Garry
2024-02-14 12:27 ` Nilay Shroff
2024-02-14 13:02 ` John Garry
2024-02-14 16:45 ` Nilay Shroff
2024-01-24 11:38 ` [PATCH v3 15/15] nvme: Ensure atomic writes will be executed atomically John Garry
2024-01-25 0:52 ` Keith Busch
2024-01-25 11:28 ` John Garry
2024-01-29 6:20 ` Christoph Hellwig
2024-01-29 9:36 ` John Garry
2024-01-29 14:39 ` Christoph Hellwig
2024-01-26 3:50 ` Chaitanya Kulkarni
2024-02-13 6:42 ` Christoph Hellwig
2024-02-13 14:07 ` John Garry
2024-01-29 6:18 ` [PATCH v3 00/15] block atomic writes Christoph Hellwig
2024-01-29 9:17 ` John Garry
2024-02-06 18:44 ` John Garry
2024-02-10 12:12 ` David Laight
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