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Tue, 20 Feb 2024 09:44:14 +1100
Date: Tue, 20 Feb 2024 09:44:14 +1100
From: Dave Chinner <david@fromorbit.com>
To: John Garry <john.g.garry@oracle.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,
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ritesh.list@gmail.com,
Prasad Singamsetty <prasad.singamsetty@oracle.com>
Subject: Re: [PATCH v4 03/11] fs: Initial atomic write support
Message-ID: <ZdPZvqLgwWSP1ppv@dread.disaster.area>
References: <20240219130109.341523-1-john.g.garry@oracle.com>
<20240219130109.341523-4-john.g.garry@oracle.com>
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In-Reply-To: <20240219130109.341523-4-john.g.garry@oracle.com>
On Mon, Feb 19, 2024 at 01:01:01PM +0000, John Garry wrote:
> @@ -3523,4 +3535,26 @@ extern int vfs_fadvise(struct file *file, loff_t offset, loff_t len,
> extern int generic_fadvise(struct file *file, loff_t offset, loff_t len,
> int advice);
>
> +static inline bool atomic_write_valid(loff_t pos, struct iov_iter *iter,
> + unsigned int unit_min, unsigned int unit_max)
> +{
> + size_t len = iov_iter_count(iter);
> +
> + if (!iter_is_ubuf(iter))
> + return false;
> +
> + if (len == unit_min || len == unit_max) {
> + /* ok if exactly min or max */
> + } else if (len < unit_min || len > unit_max) {
> + return false;
> + } else if (!is_power_of_2(len)) {
> + return false;
> + }
This doesn't need if else if else if and it doesn't need to check
for exact unit min/max matches. The exact matches require the
length to be a power of 2, so the checks are simply:
if (len < unit_min || len > unit_max)
return false;
if (!is_power_of_2(len))
return false;
> + if (pos & (len - 1))
> + return false;
This has typing issues - 64 bit value, 32 bit mask. probably should
use:
if (!IS_ALIGNED(pos, len))
return false;
-Dave.
--
Dave Chinner
david@fromorbit.com