[PATCH 22/58] xfs: remove an extent from the rmap btree

Darrick J. Wong
2015-10-07T04:57:38Z

>From : Dave Chinner <dchinner@redhat.com>

Now that we have records in the rmap btree, we need to remove them
when extents are freed. This needs to find the relevant record in
the btree and remove/trim/split it accordingly.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/libxfs/xfs_rmap.c | 154 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 153 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_rmap.c b/fs/xfs/libxfs/xfs_rmap.c
index bc25f9c..92e417d 100644
--- a/fs/xfs/libxfs/xfs_rmap.c
+++ b/fs/xfs/libxfs/xfs_rmap.c
@@ -118,6 +118,31 @@ xfs_rmap_get_rec(
return 0;
}

+/*
+ * Find the extent in the rmap btree and remove it.
+ *
+ * The record we find should always span a range greater than or equal to the
+ * the extent being freed. This makes the code simple as, in theory, we do not
+ * have to handle ranges that are split across multiple records as extents that
+ * result in bmap btree extent merges should also result in rmap btree extent
+ * merges. The owner field ensures we don't merge extents from different
+ * structures into the same record, hence this property should always hold true
+ * if we ensure that the rmap btree supports at least the same size maximum
+ * extent as the bmap btree (bmbt MAXEXTLEN is 2^21 blocks at present, rmap
+ * btree record can hold 2^32 blocks in a single extent).
+ *
+ * Special Case #1: when growing the filesystem, we "free" an extent when
+ * growing the last AG. This extent is new space and so it is not tracked as
+ * used space in the btree. The growfs code will pass in an owner of
+ * XFS_RMAP_OWN_NULL to indicate that it expected that there is no owner of this
+ * extent. We verify that - the extent lookup result in a record that does not
+ * overlap.
+ *
+ * Special Case #2: EFIs do not record the owner of the extent, so when
+ * recovering EFIs from the log we pass in XFS_RMAP_OWN_UNKNOWN to tell the rmap
+ * btree to ignore the owner (i.e. wildcard match) so we don't trigger
+ * corruption checks during log recovery.
+ */
int
xfs_rmap_free(
struct xfs_trans *tp,
@@ -128,19 +153,146 @@ xfs_rmap_free(
struct xfs_owner_info *oinfo)
{
struct xfs_mount *mp = tp->t_mountp;
+ struct xfs_btree_cur *cur;
+ struct xfs_rmap_irec ltrec;
int error = 0;
+ int i;

if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
return 0;

trace_xfs_rmap_free_extent(mp, agno, bno, len, oinfo);
- if (1)
+ cur = xfs_rmapbt_init_cursor(mp, tp, agbp, agno);
+
+ /*
+ * We should always have a left record because there's a static record
+ * for the AG headers at rm_startblock == 0 created by mkfs/growfs that
+ * will not ever be removed from the tree.
+ */
+ error = xfs_rmap_lookup_le(cur, bno, len, owner, &i);
+ if (error)
+ goto out_error;
+ XFS_WANT_CORRUPTED_GOTO(mp, i == 1, out_error);
+
+ error = xfs_rmap_get_rec(cur, &ltrec, &i);
+ if (error)
goto out_error;
+ XFS_WANT_CORRUPTED_GOTO(mp, i == 1, out_error);
+
+ /*
+ * For growfs, the incoming extent must be beyond the left record we
+ * just found as it is new space and won't be used by anyone. This is
+ * just a corruption check as we don't actually do anything with this
+ * extent.
+ */
+ if (owner == XFS_RMAP_OWN_NULL) {
+ XFS_WANT_CORRUPTED_GOTO(mp, bno > ltrec.rm_startblock +
+ ltrec.rm_blockcount, out_error);
+ goto out_done;
+ }
+
+/*
+ if (owner != ltrec.rm_owner ||
+ bno > ltrec.rm_startblock + ltrec.rm_blockcount)
+ */
+ //printk("rmfree ag %d bno 0x%x/0x%x/0x%llx, ltrec 0x%x/0x%x/0x%llx\n",
+ // agno, bno, len, owner, ltrec.rm_startblock,
+ // ltrec.rm_blockcount, ltrec.rm_owner);
+
+ /* make sure the extent we found covers the entire freeing range. */
+ XFS_WANT_CORRUPTED_GOTO(mp, ltrec.rm_startblock <= bno, out_error);
+ XFS_WANT_CORRUPTED_GOTO(mp, ltrec.rm_blockcount >= len, out_error);
+ XFS_WANT_CORRUPTED_GOTO(mp,
+ bno <= ltrec.rm_startblock + ltrec.rm_blockcount, out_error);
+
+ /* make sure the owner matches what we expect to find in the tree */
+ XFS_WANT_CORRUPTED_GOTO(mp, owner == ltrec.rm_owner ||
+ (owner < XFS_RMAP_OWN_NULL &&
+ owner >= XFS_RMAP_OWN_MIN), out_error);
+
+ if (ltrec.rm_startblock == bno && ltrec.rm_blockcount == len) {
+ //printk("remove exact\n");
+ /* exact match, simply remove the record from rmap tree */
+ error = xfs_btree_delete(cur, &i);
+ if (error)
+ goto out_error;
+ XFS_WANT_CORRUPTED_GOTO(mp, i == 1, out_error);
+ } else if (ltrec.rm_startblock == bno) {
+ //printk("remove left\n");
+ /*
+ * overlap left hand side of extent: move the start, trim the
+ * length and update the current record.
+ *
+ * ltbno ltlen
+ * Orig: |oooooooooooooooooooo|
+ * Freeing: |fffffffff|
+ * Result: |rrrrrrrrrr|
+ * bno len
+ */
+ ltrec.rm_startblock += len;
+ ltrec.rm_blockcount -= len;
+ error = xfs_rmap_update(cur, &ltrec);
+ if (error)
+ goto out_error;
+ } else if (ltrec.rm_startblock + ltrec.rm_blockcount == bno + len) {
+ //printk("remove right\n");
+ /*
+ * overlap right hand side of extent: trim the length and update
+ * the current record.
+ *
+ * ltbno ltlen
+ * Orig: |oooooooooooooooooooo|
+ * Freeing: |fffffffff|
+ * Result: |rrrrrrrrrr|
+ * bno len
+ */
+ ltrec.rm_blockcount -= len;
+ error = xfs_rmap_update(cur, &ltrec);
+ if (error)
+ goto out_error;
+ } else {
+
+ /*
+ * overlap middle of extent: trim the length of the existing
+ * record to the length of the new left-extent size, increment
+ * the insertion position so we can insert a new record
+ * containing the remaining right-extent space.
+ *
+ * ltbno ltlen
+ * Orig: |oooooooooooooooooooo|
+ * Freeing: |fffffffff|
+ * Result: |rrrrr| |rrrr|
+ * bno len
+ */
+ xfs_extlen_t orig_len = ltrec.rm_blockcount;
+ //printk("remove middle\n");
+
+ ltrec.rm_blockcount = bno - ltrec.rm_startblock;;
+ error = xfs_rmap_update(cur, &ltrec);
+ if (error)
+ goto out_error;
+
+ error = xfs_btree_increment(cur, 0, &i);
+ if (error)
+ goto out_error;
+
+ cur->bc_rec.r.rm_startblock = bno + len;
+ cur->bc_rec.r.rm_blockcount = orig_len - len -
+ ltrec.rm_blockcount;
+ cur->bc_rec.r.rm_owner = ltrec.rm_owner;
+ error = xfs_btree_insert(cur, &i);
+ if (error)
+ goto out_error;
+ }
+
+out_done:
trace_xfs_rmap_free_extent_done(mp, agno, bno, len, oinfo);
+ xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
return 0;

out_error:
trace_xfs_rmap_free_extent_error(mp, agno, bno, len, oinfo);
+ xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
return error;