btrfs: count super block write errors in device instead of tracking folio error state

Currently the error status of super block write is tracked in page/folio
status bit Error. For that we need to keep the reference for the whole
duration of write and wait.

Count the number of superblock writeback errors in the btrfs_device.
That means we don't need the folio to stay around until it's waited for,
and can avoid the extra call to folio_get/put.

Also remove a mention of PageError in a comment as it's the last mention
of the page Error state.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index cf555f5b47ce..66e6fc481ecd 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -92,6 +92,9 @@ enum btrfs_raid_types {
 #define BTRFS_DEV_STATE_FLUSH_SENT	(4)
 #define BTRFS_DEV_STATE_NO_READA	(5)
 
+/* Special value encoding failure to write primary super block. */
+#define BTRFS_SUPER_PRIMARY_WRITE_ERROR		(INT_MAX / 2)
+
 struct btrfs_fs_devices;
 
 struct btrfs_device {
@@ -142,6 +145,12 @@ struct btrfs_device {
 	/* type and info about this device */
 	u64 type;
 
+	/*
+	 * Counter of super block write errors, values larger than
+	 * BTRFS_SUPER_PRIMARY_WRITE_ERROR encode primary super block write failure.
+	 */
+	atomic_t sb_write_errors;
+
 	/* minimal io size for this device */
 	u32 sector_size;