linux-kernel - [PATCH 5.15 08/20] btrfs: zoned: use regular writes for relocation

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Date:   Fri, 19 Nov 2021 18:39:26 +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, Naohiro Aota <naohiro.aota@....com>,
        Johannes Thumshirn <johannes.thumshirn@....com>,
        David Sterba <dsterba@...e.com>
Subject: [PATCH 5.15 08/20] btrfs: zoned: use regular writes for relocation

From: Johannes Thumshirn <johannes.thumshirn@....com>

commit e6d261e3b1f777b499ce8f535ed44dd1b69278b7 upstream

Now that we have a dedicated block group for relocation, we can use
REQ_OP_WRITE instead of  REQ_OP_ZONE_APPEND for writing out the data on
relocation.

Reviewed-by: Naohiro Aota <naohiro.aota@....com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@....com>
Reviewed-by: David Sterba <dsterba@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/btrfs/zoned.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -1304,6 +1304,17 @@ bool btrfs_use_zone_append(struct btrfs_
 	if (!is_data_inode(&inode->vfs_inode))
 		return false;
 
+	/*
+	 * Using REQ_OP_ZONE_APPNED for relocation can break assumptions on the
+	 * extent layout the relocation code has.
+	 * Furthermore we have set aside own block-group from which only the
+	 * relocation "process" can allocate and make sure only one process at a
+	 * time can add pages to an extent that gets relocated, so it's safe to
+	 * use regular REQ_OP_WRITE for this special case.
+	 */
+	if (btrfs_is_data_reloc_root(inode->root))
+		return false;
+
 	cache = btrfs_lookup_block_group(fs_info, start);
 	ASSERT(cache);
 	if (!cache)