From: Christoph Hellwig <hch@infradead.org>
To: Chandan Babu R <chandanrlinux@gmail.com>
Cc: linux-xfs@vger.kernel.org, darrick.wong@oracle.com, david@fromorbit.com
Subject: Re: [PATCH V6 08/11] xfs: Check for extent overflow when remapping an extent
Date: Thu, 15 Oct 2020 09:39:45 +0100 [thread overview]
Message-ID: <20201015083945.GH5902@infradead.org> (raw)
In-Reply-To: <20201012092938.50946-9-chandanrlinux@gmail.com>
This patch demonstrates very well why I think having these magic
defines and the comments in a header makes no sense.
> +/*
> + * Remapping an extent involves unmapping the existing extent and mapping in the
> + * new extent.
> + *
> + * When unmapping, an extent containing the entire unmap range can be split into
> + * two extents,
> + * i.e. | Old extent | hole | Old extent |
> + * Hence extent count increases by 1.
> + *
> + * Mapping in the new extent into the destination file can increase the extent
> + * count by 1.
> + */
> +#define XFS_IEXT_REFLINK_REMAP_CNT(smap_real, dmap_written) \
> + (((smap_real) ? 1 : 0) + ((dmap_written) ? 1 : 0))
> +
> /*
> * Fork handling.
> */
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 4f0198f636ad..c9f9ff68b5bb 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -1099,6 +1099,11 @@ xfs_reflink_remap_extent(
> goto out_cancel;
> }
>
> + error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
> + XFS_IEXT_REFLINK_REMAP_CNT(smap_real, dmap_written));
> + if (error)
> + goto out_cancel;
> +
This is a completely mess.
If OTOH xfs_reflink_remap_extent had a local variable for the potential
max number of extents, which is incremented near the initialization
of smap_real and dmap_written, with a nice comment near to each
increment it would make complete sense to the reader.
next prev parent reply other threads:[~2020-10-15 8:39 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-12 9:29 [PATCH V6 00/11] Bail out if transaction can cause extent count to overflow Chandan Babu R
2020-10-12 9:29 ` [PATCH V6 01/11] xfs: Add helper for checking per-inode extent count overflow Chandan Babu R
2020-10-15 8:34 ` Christoph Hellwig
2020-10-12 9:29 ` [PATCH V6 02/11] xfs: Check for extent overflow when trivally adding a new extent Chandan Babu R
2020-10-15 8:34 ` Christoph Hellwig
2020-10-12 9:29 ` [PATCH V6 03/11] xfs: Check for extent overflow when punching a hole Chandan Babu R
2020-10-15 8:35 ` Christoph Hellwig
2020-10-12 9:29 ` [PATCH V6 04/11] xfs: Check for extent overflow when adding/removing xattrs Chandan Babu R
2020-10-15 8:36 ` Christoph Hellwig
2020-10-12 9:29 ` [PATCH V6 05/11] xfs: Check for extent overflow when adding/removing dir entries Chandan Babu R
2020-10-15 8:36 ` Christoph Hellwig
2020-10-12 9:29 ` [PATCH V6 06/11] xfs: Check for extent overflow when writing to unwritten extent Chandan Babu R
2020-10-15 8:36 ` Christoph Hellwig
2020-10-12 9:29 ` [PATCH V6 07/11] xfs: Check for extent overflow when moving extent from cow to data fork Chandan Babu R
2020-10-15 8:37 ` Christoph Hellwig
2020-10-12 9:29 ` [PATCH V6 08/11] xfs: Check for extent overflow when remapping an extent Chandan Babu R
2020-10-15 8:39 ` Christoph Hellwig [this message]
2020-10-15 10:01 ` Chandan Babu R
2020-10-15 18:45 ` Darrick J. Wong
2020-10-16 4:27 ` Chandan Babu R
2020-10-16 7:04 ` Christoph Hellwig
2020-10-16 11:28 ` Chandan Babu R
2020-10-16 15:29 ` Darrick J. Wong
2020-10-17 2:55 ` Chandan Babu R
2020-10-12 9:29 ` [PATCH V6 09/11] xfs: Check for extent overflow when swapping extents Chandan Babu R
2020-10-12 9:29 ` [PATCH V6 10/11] xfs: Introduce error injection to reduce maximum inode fork extent count Chandan Babu R
2020-10-15 8:40 ` Christoph Hellwig
2020-10-12 9:29 ` [PATCH V6 11/11] xfs: Introduce error injection to allocate only minlen size extents for files Chandan Babu R
2020-10-15 8:41 ` Christoph Hellwig
2020-10-15 10:02 ` Chandan Babu R
2020-10-15 18:41 ` Darrick J. Wong
2020-10-16 11:31 ` Chandan Babu R
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