From: John Garry <john.g.garry@oracle.com>
To: Dave Chinner <david@fromorbit.com>
Cc: axboe@kernel.dk, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me,
jejb@linux.ibm.com, martin.petersen@oracle.com,
djwong@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org,
dchinner@redhat.com, jack@suse.cz, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
linux-fsdevel@vger.kernel.org, tytso@mit.edu, jbongio@google.com,
linux-scsi@vger.kernel.org, ojaswin@linux.ibm.com,
linux-aio@kvack.org, linux-btrfs@vger.kernel.org,
io-uring@vger.kernel.org, nilay@linux.ibm.com,
ritesh.list@gmail.com
Subject: Re: [PATCH v4 05/11] block: Add core atomic write support
Date: Tue, 20 Feb 2024 10:01:38 +0000 [thread overview]
Message-ID: <f5ccbfac-e369-4371-bb7f-68bb40c47239@oracle.com> (raw)
In-Reply-To: <ZdPdHzNAVb5hqlkY@dread.disaster.area>
On 19/02/2024 22:58, Dave Chinner wrote:
> On Mon, Feb 19, 2024 at 01:01:03PM +0000, John Garry wrote:
>> Add atomic write support as follows:
>> diff --git a/block/blk-merge.c b/block/blk-merge.c
>> index 74e9e775f13d..12a75a252ca2 100644
>> --- a/block/blk-merge.c
>> +++ b/block/blk-merge.c
>> @@ -18,6 +18,42 @@
>> #include "blk-rq-qos.h"
>> #include "blk-throttle.h"
>>
>> +static bool rq_straddles_atomic_write_boundary(struct request *rq,
>> + unsigned int front,
>> + unsigned int back)
>> +{
>> + unsigned int boundary = queue_atomic_write_boundary_bytes(rq->q);
>> + unsigned int mask, imask;
>> + loff_t start, end;
>> +
>> + if (!boundary)
>> + return false;
>> +
>> + start = rq->__sector << SECTOR_SHIFT;
>> + end = start + rq->__data_len;
>> +
>> + start -= front;
>> + end += back;
>> +
>> + /* We're longer than the boundary, so must be crossing it */
>> + if (end - start > boundary)
>> + return true;
>> +
>> + mask = boundary - 1;
>> +
>> + /* start/end are boundary-aligned, so cannot be crossing */
>> + if (!(start & mask) || !(end & mask))
>> + return false;
>> +
>> + imask = ~mask;
>> +
>> + /* Top bits are different, so crossed a boundary */
>> + if ((start & imask) != (end & imask))
>> + return true;
>> +
>> + return false;
>> +}
> I have no way of verifying this function is doing what it is
> supposed to because it's function is undocumented. I have no idea
> what the front/back variables are supposed to represent, and so no
> clue if they are being applied properly.
I'll add proper function header documentation.
>
> That said, it's also applying unsigned 32 bit mask variables to
> signed 64 bit quantities and trying to do things like "high bit changed"
> checks on the 64 bit variable. This just smells like a future
> source of "large offsets don't work like we expected!" bugs.
I'll change variables to be unsigned and also all the same size.
>
>> diff --git a/block/blk-settings.c b/block/blk-settings.c
>> index 06ea91e51b8b..176f26374abc 100644
>> --- a/block/blk-settings.c
>> +++ b/block/blk-settings.c
>> @@ -59,6 +59,13 @@ void blk_set_default_limits(struct queue_limits *lim)
>> lim->zoned = false;
>> lim->zone_write_granularity = 0;
>> lim->dma_alignment = 511;
>> + lim->atomic_write_hw_max_sectors = 0;
>> + lim->atomic_write_max_sectors = 0;
>> + lim->atomic_write_hw_boundary_sectors = 0;
>> + lim->atomic_write_hw_unit_min_sectors = 0;
>> + lim->atomic_write_unit_min_sectors = 0;
>> + lim->atomic_write_hw_unit_max_sectors = 0;
>> + lim->atomic_write_unit_max_sectors = 0;
>> }
> Seems to me this function would do better to just
>
> memset(lim, 0, sizeof(*lim));
>
> and then set all the non-zero fields.
Christoph responded about limits here and in
blk_queue_atomic_write_max_bytes(), so please let me know if still some
concerns.
Thanks,
John
next prev parent reply other threads:[~2024-02-20 10:02 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-19 13:00 [PATCH v4 00/11] block atomic writes John Garry
2024-02-19 13:00 ` [PATCH v4 01/11] block: Pass blk_queue_get_max_sectors() a request pointer John Garry
2024-02-19 18:57 ` Keith Busch
2024-02-19 13:01 ` [PATCH v4 02/11] block: Call blkdev_dio_unaligned() from blkdev_direct_IO() John Garry
2024-02-19 18:57 ` Keith Busch
2024-02-20 8:31 ` John Garry
2024-02-20 6:54 ` Christoph Hellwig
2024-02-19 13:01 ` [PATCH v4 03/11] fs: Initial atomic write support John Garry
2024-02-19 19:16 ` David Sterba
2024-02-20 8:13 ` John Garry
2024-02-19 22:44 ` Dave Chinner
2024-02-20 9:52 ` John Garry
2024-02-24 18:16 ` Ritesh Harjani
2024-02-24 18:20 ` Ritesh Harjani
2024-02-26 8:58 ` John Garry
2024-02-26 9:13 ` Ritesh Harjani
2024-02-26 9:46 ` John Garry
2024-02-26 8:51 ` John Garry
2024-02-19 13:01 ` [PATCH v4 04/11] fs: Add initial atomic write support info to statx John Garry
2024-02-19 22:28 ` Dave Chinner
2024-02-20 9:40 ` John Garry
2024-02-20 8:20 ` Christoph Hellwig
2024-02-20 9:01 ` John Garry
2024-02-24 18:46 ` Ritesh Harjani
2024-02-26 9:07 ` John Garry
2024-02-19 13:01 ` [PATCH v4 05/11] block: Add core atomic write support John Garry
2024-02-19 22:58 ` Dave Chinner
2024-02-20 8:22 ` Christoph Hellwig
2024-02-20 10:01 ` John Garry [this message]
2024-02-25 12:09 ` Ritesh Harjani
2024-02-25 12:21 ` Ritesh Harjani
2024-02-26 9:23 ` John Garry
2024-02-19 13:01 ` [PATCH v4 06/11] block: Add atomic write support for statx John Garry
2024-02-20 8:29 ` Christoph Hellwig
2024-02-20 9:35 ` John Garry
2024-02-25 14:20 ` Ritesh Harjani
2024-02-26 9:36 ` John Garry
2024-02-19 13:01 ` [PATCH v4 07/11] block: Add fops atomic write support John Garry
2024-02-25 14:46 ` Ritesh Harjani
2024-02-26 9:46 ` John Garry
2024-02-19 13:01 ` [PATCH v4 08/11] scsi: sd: Atomic " John Garry
2024-02-19 13:01 ` [PATCH v4 09/11] scsi: scsi_debug: " John Garry
2024-02-20 7:12 ` Ojaswin Mujoo
2024-02-20 9:01 ` John Garry
2024-02-19 13:01 ` [PATCH v4 10/11] nvme: " John Garry
2024-02-19 19:21 ` Keith Busch
2024-02-20 6:55 ` Christoph Hellwig
2024-02-20 8:19 ` John Garry
2024-02-20 8:31 ` Christoph Hellwig
2024-02-20 8:50 ` John Garry
2024-02-19 13:01 ` [PATCH v4 11/11] nvme: Ensure atomic writes will be executed atomically John Garry
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