xfs: refactor realtime scrubbing context management

Create a pair of helpers to deal with setting up the necessary incore
context to check metadata records against the realtime metadata.  Right
now this is limited to locking the realtime bitmap and summary inodes,
but as we add rmap and reflink to the realtime device this will grow to
include btree cursors.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>

7 files changed, 55 insertions, 23 deletions

diff --git a/fs/xfs/scrub/bmap.c b/fs/xfs/scrub/bmap.c
index 735884e7d315..81beb8e7e504 100644
--- a/fs/xfs/scrub/bmap.c
+++ b/fs/xfs/scrub/bmap.c
@@ -310,8 +310,12 @@ xchk_bmap_rt_iextent_xref(
 	struct xchk_bmap_info	*info,
 	struct xfs_bmbt_irec	*irec)
 {
+	xchk_rt_init(info->sc, &info->sc->sr);
+
 	xchk_xref_is_used_rt_space(info->sc, irec->br_startblock,
 			irec->br_blockcount);
+
+	xchk_rt_unlock(info->sc, &info->sc->sr);
 }
 
 /* Cross-reference a single datadev extent record. */
diff --git a/fs/xfs/scrub/common.c b/fs/xfs/scrub/common.c
index 43888326bccc..6575d5392d0d 100644
--- a/fs/xfs/scrub/common.c
+++ b/fs/xfs/scrub/common.c
@@ -598,6 +598,39 @@ xchk_ag_init(
 	return 0;
 }
 
+/*
+ * For scrubbing a realtime file, grab all the in-core resources we'll need to
+ * check the realtime metadata, which means taking the ILOCK of the realtime
+ * metadata inodes.  Callers must not join these inodes to the transaction
+ * with non-zero lockflags or concurrency problems will result.
+ */
+void
+xchk_rt_init(
+	struct xfs_scrub	*sc,
+	struct xchk_rt		*sr)
+{
+	xfs_ilock(sc->mp->m_rbmip, XFS_ILOCK_EXCL | XFS_ILOCK_RTBITMAP);
+	xfs_ilock(sc->mp->m_rsumip, XFS_ILOCK_EXCL | XFS_ILOCK_RTSUM);
+	sr->locked = true;
+}
+
+/*
+ * Unlock the realtime metadata inodes.  This must be done /after/ committing
+ * (or cancelling) the scrub transaction.
+ */
+void
+xchk_rt_unlock(
+	struct xfs_scrub	*sc,
+	struct xchk_rt		*sr)
+{
+	if (!sr->locked)
+		return;
+
+	xfs_iunlock(sc->mp->m_rsumip, XFS_ILOCK_EXCL);
+	xfs_iunlock(sc->mp->m_rbmip, XFS_ILOCK_EXCL);
+	sr->locked = false;
+}
+
 /* Per-scrubber setup functions */
 
 void
diff --git a/fs/xfs/scrub/common.h b/fs/xfs/scrub/common.h
index 4daff036b9cb..263dbd9e5b46 100644
--- a/fs/xfs/scrub/common.h
+++ b/fs/xfs/scrub/common.h
@@ -142,6 +142,8 @@ xchk_ag_init_existing(
 	return error == -ENOENT ? -EFSCORRUPTED : error;
 }
 
+void xchk_rt_init(struct xfs_scrub *sc, struct xchk_rt *sr);
+void xchk_rt_unlock(struct xfs_scrub *sc, struct xchk_rt *sr);
 int xchk_ag_read_headers(struct xfs_scrub *sc, xfs_agnumber_t agno,
 		struct xchk_ag *sa);
 void xchk_ag_btcur_free(struct xchk_ag *sa);
diff --git a/fs/xfs/scrub/rtbitmap.c b/fs/xfs/scrub/rtbitmap.c
index 5ceff1d9c611..1ff6014f0d3b 100644
--- a/fs/xfs/scrub/rtbitmap.c
+++ b/fs/xfs/scrub/rtbitmap.c
@@ -32,7 +32,7 @@ xchk_setup_rtbitmap(
 	if (error)
 		return error;
 
-	xchk_ilock(sc, XFS_ILOCK_EXCL | XFS_ILOCK_RTBITMAP);
+	xchk_rt_init(sc, &sc->sr);
 	return 0;
 }
 
@@ -144,13 +144,10 @@ xchk_xref_is_used_rt_space(
 	do_div(startext, sc->mp->m_sb.sb_rextsize);
 	do_div(endext, sc->mp->m_sb.sb_rextsize);
 	extcount = endext - startext + 1;
-	xfs_ilock(sc->mp->m_rbmip, XFS_ILOCK_SHARED | XFS_ILOCK_RTBITMAP);
 	error = xfs_rtalloc_extent_is_free(sc->mp, sc->tp, startext, extcount,
 			&is_free);
 	if (!xchk_should_check_xref(sc, &error, NULL))
-		goto out_unlock;
+		return;
 	if (is_free)
 		xchk_ino_xref_set_corrupt(sc, sc->mp->m_rbmip->i_ino);
-out_unlock:
-	xfs_iunlock(sc->mp->m_rbmip, XFS_ILOCK_SHARED | XFS_ILOCK_RTBITMAP);
 }
diff --git a/fs/xfs/scrub/rtsummary.c b/fs/xfs/scrub/rtsummary.c
index b8fb3923f7f7..be5ec3e8bf12 100644
--- a/fs/xfs/scrub/rtsummary.c
+++ b/fs/xfs/scrub/rtsummary.c
@@ -71,14 +71,7 @@ xchk_setup_rtsummary(
 	if (error)
 		return error;
 
-	/*
-	 * Locking order requires us to take the rtbitmap first.  We must be
-	 * careful to unlock it ourselves when we are done with the rtbitmap
-	 * file since the scrub infrastructure won't do that for us.  Only
-	 * then we can lock the rtsummary inode.
-	 */
-	xfs_ilock(mp->m_rbmip, XFS_ILOCK_SHARED | XFS_ILOCK_RTBITMAP);
-	xchk_ilock(sc, XFS_ILOCK_EXCL | XFS_ILOCK_RTSUM);
+	xchk_rt_init(sc, &sc->sr);
 	return 0;
 }
 
@@ -216,7 +209,7 @@ xchk_rtsummary(
 	/* Invoke the fork scrubber. */
 	error = xchk_metadata_inode_forks(sc);
 	if (error || (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT))
-		goto out_rbm;
+		return error;
 
 	/* Construct the new summary file from the rtbitmap. */
 	error = xchk_rtsum_compute(sc);
@@ -226,17 +219,11 @@ xchk_rtsummary(
 		 * error since we're checking the summary file.
 		 */
 		xchk_ino_xref_set_corrupt(sc, mp->m_rbmip->i_ino);
-		error = 0;
-		goto out_rbm;
+		return 0;
 	}
 	if (error)
-		goto out_rbm;
+		return error;
 
 	/* Does the computed summary file match the actual rtsummary file? */
-	error = xchk_rtsum_compare(sc);
-
-out_rbm:
-	/* Unlock the rtbitmap since we're done with it. */
-	xfs_iunlock(mp->m_rbmip, XFS_ILOCK_SHARED | XFS_ILOCK_RTBITMAP);
-	return error;
+	return xchk_rtsum_compare(sc);
 }
diff --git a/fs/xfs/scrub/scrub.c b/fs/xfs/scrub/scrub.c
index 35f0c1888d47..d7756680aee8 100644
--- a/fs/xfs/scrub/scrub.c
+++ b/fs/xfs/scrub/scrub.c
@@ -165,6 +165,7 @@ xchk_teardown(
 			xfs_trans_cancel(sc->tp);
 		sc->tp = NULL;
 	}
+	xchk_rt_unlock(sc, &sc->sr);
 	if (sc->ip) {
 		if (sc->ilock_flags)
 			xchk_iunlock(sc, sc->ilock_flags);
diff --git a/fs/xfs/scrub/scrub.h b/fs/xfs/scrub/scrub.h
index b164dd094187..c88279780fe4 100644
--- a/fs/xfs/scrub/scrub.h
+++ b/fs/xfs/scrub/scrub.h
@@ -59,6 +59,11 @@ struct xchk_ag {
 	struct xfs_btree_cur	*refc_cur;
 };
 
+/* Btree cursors for the RT volume. */
+struct xchk_rt {
+	bool			locked;
+};
+
 struct xfs_scrub {
 	/* General scrub state. */
 	struct xfs_mount		*mp;
@@ -114,6 +119,9 @@ struct xfs_scrub {
 
 	/* State tracking for single-AG operations. */
 	struct xchk_ag			sa;
+
+	/* State tracking for realtime operations. */
+	struct xchk_rt			sr;
 };
 
 /* XCHK state flags grow up from zero, XREP state flags grown down from 2^31 */