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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Naohiro Aota <naohiro.aota@wdc.com>,
        David Sterba <dsterba@suse.com>
Subject: [PATCH 5.16 0885/1039] btrfs: add extent allocator hook to decide to allocate chunk or not
Date:   Mon, 24 Jan 2022 19:44:34 +0100
Message-Id: <20220124184155.038183447@linuxfoundation.org>
In-Reply-To: <20220124184125.121143506@linuxfoundation.org>
References: <20220124184125.121143506@linuxfoundation.org>
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From: Naohiro Aota <naohiro.aota@wdc.com>

commit 50475cd57706359d6cc652be88369dace7a4c2eb upstream.

Introduce a new hook for an extent allocator policy. With the new
hook, a policy can decide to allocate a new block group or not. If
not, it will return -ENOSPC, so btrfs_reserve_extent() will cut the
allocation size in half and retry the allocation if min_alloc_size is
large enough.

The hook has a place holder and will be replaced with the real
implementation in the next patch.

CC: stable@vger.kernel.org # 5.16
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/btrfs/extent-tree.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3947,6 +3947,19 @@ static void found_extent(struct find_fre
 	}
 }
 
+static bool can_allocate_chunk(struct btrfs_fs_info *fs_info,
+			       struct find_free_extent_ctl *ffe_ctl)
+{
+	switch (ffe_ctl->policy) {
+	case BTRFS_EXTENT_ALLOC_CLUSTERED:
+		return true;
+	case BTRFS_EXTENT_ALLOC_ZONED:
+		return true;
+	default:
+		BUG();
+	}
+}
+
 static int chunk_allocation_failed(struct find_free_extent_ctl *ffe_ctl)
 {
 	switch (ffe_ctl->policy) {
@@ -4034,6 +4047,10 @@ static int find_free_extent_update_loop(
 			struct btrfs_trans_handle *trans;
 			int exist = 0;
 
+			/*Check if allocation policy allows to create a new chunk */
+			if (!can_allocate_chunk(fs_info, ffe_ctl))
+				return -ENOSPC;
+
 			trans = current->journal_info;
 			if (trans)
 				exist = 1;