linux-kernel - [PATCH 5.16 140/164] btrfs: defrag: remove an ambiguous condition for rejection

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Date:   Mon, 28 Feb 2022 18:25:02 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Filipe Manana <fdmanana@...e.com>,
        Qu Wenruo <wqu@...e.com>, David Sterba <dsterba@...e.com>
Subject: [PATCH 5.16 140/164] btrfs: defrag: remove an ambiguous condition for rejection

From: Qu Wenruo <wqu@...e.com>

commit 550f133f6959db927127111b50e483da3a7ce662 upstream.

>>From the very beginning of btrfs defrag, there is a check to reject
extents which meet both conditions:

- Physically adjacent

  We may want to defrag physically adjacent extents to reduce the number
  of extents or the size of subvolume tree.

- Larger than 128K

  This may be there for compressed extents, but unfortunately 128K is
  exactly the max capacity for compressed extents.
  And the check is > 128K, thus it never rejects compressed extents.

  Furthermore, the compressed extent capacity bug is fixed by previous
  patch, there is no reason for that check anymore.

The original check has a very small ranges to reject (the target extent
size is > 128K, and default extent threshold is 256K), and for
compressed extent it doesn't work at all.

So it's better just to remove the rejection, and allow us to defrag
physically adjacent extents.

CC: stable@...r.kernel.org # 5.16
Reviewed-by: Filipe Manana <fdmanana@...e.com>
Signed-off-by: Qu Wenruo <wqu@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/btrfs/ioctl.c |    4 ----
 1 file changed, 4 deletions(-)

--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1049,10 +1049,6 @@ static bool defrag_check_next_extent(str
 	 */
 	if (next->len >= get_extent_max_capacity(em))
 		goto out;
-	/* Physically adjacent and large enough */
-	if ((em->block_start + em->block_len == next->block_start) &&
-	    (em->block_len > SZ_128K && next->block_len > SZ_128K))
-		goto out;
 	ret = true;
 out:
 	free_extent_map(next);