xfs: support in-memory btrees

Adapt the generic btree cursor code to be able to create a btree whose
buffers come from a (presumably in-memory) buftarg with a header block
that's specific to in-memory btrees.  We'll connect this to other parts
of online scrub in the next patches.

Note that in-memory btrees always have a block size matching the system
memory page size for efficiency reasons.  There are also a few things we
need to do to finalize a btree update; that's covered in the next patch.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

2 files changed, 8 insertions, 0 deletions

diff --git a/fs/xfs/scrub/scrub.c b/fs/xfs/scrub/scrub.c
index aeac9cae4ad4..6828e72824fb 100644
--- a/fs/xfs/scrub/scrub.c
+++ b/fs/xfs/scrub/scrub.c
@@ -15,6 +15,7 @@
 #include "xfs_quota.h"
 #include "xfs_qm.h"
 #include "xfs_scrub.h"
+#include "xfs_buf_mem.h"
 #include "scrub/scrub.h"
 #include "scrub/common.h"
 #include "scrub/trace.h"
@@ -190,6 +191,10 @@ xchk_teardown(
 		sc->flags &= ~XCHK_HAVE_FREEZE_PROT;
 		mnt_drop_write_file(sc->file);
 	}
+	if (sc->xmbtp) {
+		xmbuf_free(sc->xmbtp);
+		sc->xmbtp = NULL;
+	}
 	if (sc->xfile) {
 		xfile_destroy(sc->xfile);
 		sc->xfile = NULL;
diff --git a/fs/xfs/scrub/scrub.h b/fs/xfs/scrub/scrub.h
index f99a3c21d02e..1247284c17a0 100644
--- a/fs/xfs/scrub/scrub.h
+++ b/fs/xfs/scrub/scrub.h
@@ -99,6 +99,9 @@ struct xfs_scrub {
 	/* xfile used by the scrubbers; freed at teardown. */
 	struct xfile			*xfile;
 
+	/* buffer target for in-memory btrees; also freed at teardown. */
+	struct xfs_buftarg		*xmbtp;
+
 	/* Lock flags for @ip. */
 	uint				ilock_flags;