xfs
[Top] [All Lists]

Re: [PATCH 3/3] xfs: byte range granularity for XFS_IOC_ZERO_RANGE

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 3/3] xfs: byte range granularity for XFS_IOC_ZERO_RANGE
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Fri, 23 Nov 2012 03:34:03 -0500
Cc: xfs@xxxxxxxxxxx
In-reply-to: <1353641065-14983-4-git-send-email-david@xxxxxxxxxxxxx>
References: <1353641065-14983-1-git-send-email-david@xxxxxxxxxxxxx> <1353641065-14983-4-git-send-email-david@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Fri, Nov 23, 2012 at 02:24:25PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
> 
> XFS_IOC_ZERO_RANGE simply does not work properly for non page cache
> aligned ranges. Neither test 242 or 290 exercise this correctly, so
> the behaviour is completely busted even though the tests pass.
> 
> Fix it to support full byte range granularity as was originally
> intended for this ioctl.

Looks good, but a couple cosmetic comments below:

> +     rounding = max_t(uint, 1 << mp->m_sb.sb_blocklog, PAGE_CACHE_SIZE);

I'd call this granularity.

> +     /* round the range iof extents we are going to convert inwards */
> +     start = round_up(offset, rounding);
> +     end = round_down(offset + len, rounding);

start_boundary, end_boundary?

> +     if (start < end - 1) {
> +             /* punch out the page cache over the conversion range */
> +             truncate_pagecache_range(VFS_I(ip), start, end - 1);
> +             /* convert the blocks */
> +             error = xfs_alloc_file_space(ip, start, end - start - 1,
> +                                 XFS_BMAPI_PREALLOC | XFS_BMAPI_CONVERT,
> +                                 attr_flags);
> +             if (error)
> +                     goto out_unlock;
> +     } else {
> +             /* it's a sub-rounding range */
> +             ASSERT(offset + len <= start);
> +             error = xfs_iozero(ip, offset, len);
> +             goto out_unlock;
> +     }
> +
> +     /* now we've handled the interior of the range, handle the edges */
> +     if (start != offset)
> +             error = xfs_iozero(ip, offset, start - offset);
> +     if (!error && end != offset + len)
> +             error = xfs_iozero(ip, end, offset + len - end);

I'd move the edge iozero calls into the if branch, that gives a natural
code flow and avoids the goto unlock in the sub-page case.

<Prev in Thread] Current Thread [Next in Thread>