Re: [PATCH v2 06/14] fs: xfs: Do not free EOF blocks for forcealign

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  	 */
  	end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)XFS_ISIZE(ip));
-	if (XFS_IS_REALTIME_INODE(ip) && mp->m_sb.sb_rextsize > 1)
+
+	/* Do not free blocks when forcing extent sizes */

That comment seems wrong - this just rounds up where we start
trimming from to be aligned...

ok


+	if (xfs_get_extsz(ip) > 1)
+		end_fsb = roundup_64(end_fsb, xfs_get_extsz(ip));
+	else if (XFS_IS_REALTIME_INODE(ip) && mp->m_sb.sb_rextsize > 1)
  		end_fsb = xfs_rtb_roundup_rtx(mp, end_fsb);

I think this would be better written as:

	/*
	 * Forced extent alignment requires us to round up where we
	 * start trimming from so that result is correctly aligned.
	 */
	if (xfs_inode_forcealign(ip)) {
		if (ip->i_extsize > 1)
			end_fsb = roundup_64(end_fsb, ip->i_extsize);
		else if (XFS_IS_REALTIME_INODE(ip) && mp->m_sb.sb_rextsize > 1)
			end_fsb = xfs_rtb_roundup_rtx(mp, end_fsb);
	}

Because we only want end-fsb alignment when forced alignment is
required.

But why change current rtvol behaviour?


Which then makes me wonder: truncate needs this, too, doesn't it?
And the various fallocate() ops like hole punching and extent
shifting?


Yes, I would think so. I quickly checked rtvol for truncate and it does the round up. I would need to check the relevant code for truncate and fallocate for forcealign now.

I do also wonder if we could factor out this rounding up code for truncate, facallocate, and whatever else.

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 2c439df8c47f..bbb8886f1d32 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -65,6 +65,20 @@ xfs_get_extsz_hint(
  	return 0;
  }
+/*
+ * Helper function to extract extent size. It will return a power-of-2,
+ * as forcealign requires this.
+ */
+xfs_extlen_t
+xfs_get_extsz(
+	struct xfs_inode	*ip)
+{
+	if (xfs_inode_forcealign(ip) && ip->i_extsize)
+		return ip->i_extsize;
+
+	return 1;
+}

This can go away - if it is needed elsewhere, then I think it would
be better open coded because it better documents what the code is
doing...


I would rather get rid of xfs_get_extsz() for sure.

Thanks,
John





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