Create a function to enable querying of btree records mapping to a
range of keys. This will be used in subsequent patches to allow
querying the reverse mapping btree to find the extents mapped to a
range of physical blocks, though the generic code can be used for
any range query.
v2: add some shortcuts so that we can jump out of processing once
we know there won't be any more records to find.
v3: document the range query algorithm, refactor the pop-up code,
fix the diff_two_keys usage.
v4: The overlapped query range function should use the btree get_block
helper because the root block could be an inode, in which case
bc_bufs[nlevels-1] will be NULL. Refactor the key calculations
so that we can return -EINVAL if low > high.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
fs/xfs/libxfs/xfs_btree.c | 264 +++++++++++++++++++++++++++++++++++++++++++++
fs/xfs/libxfs/xfs_btree.h | 22 +++-
fs/xfs/xfs_trace.h | 1
3 files changed, 282 insertions(+), 5 deletions(-)
diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index 1881536..3780128 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -4522,3 +4522,267 @@ xfs_btree_compute_maxlevels(
maxblocks = (maxblocks + limits[1] - 1) / limits[1];
return level;
}
+
+/*
+ * Query a regular btree for all records overlapping a given interval.
+ * Start with a LE lookup of the key of low_rec and return all records
+ * until we find a record with a key greater than the key of high_rec.
+ */
+STATIC int
+xfs_btree_simple_query_range(
+ struct xfs_btree_cur *cur,
+ union xfs_btree_key *low_key,
+ union xfs_btree_key *high_key,
+ xfs_btree_query_range_fn fn,
+ void *priv)
+{
+ union xfs_btree_rec *recp;
+ union xfs_btree_key rec_key;
+ __int64_t diff;
+ int stat;
+ bool firstrec = true;
+ int error;
+
+ ASSERT(cur->bc_ops->init_high_key_from_rec);
+ ASSERT(cur->bc_ops->diff_two_keys);
+
+ /*
+ * Find the leftmost record. The btree cursor must be set
+ * to the low record used to generate low_key.
+ */
+ stat = 0;
+ error = xfs_btree_lookup(cur, XFS_LOOKUP_LE, &stat);
+ if (error)
+ goto out;
+
+ while (stat) {
+ /* Find the record. */
+ error = xfs_btree_get_rec(cur, &recp, &stat);
+ if (error || !stat)
+ break;
+ cur->bc_ops->init_high_key_from_rec(&rec_key, recp);
+
+ /* Skip if high_key(rec) < low_key. */
+ if (firstrec) {
+ firstrec = false;
+ diff = cur->bc_ops->diff_two_keys(cur, low_key,
+ &rec_key);
+ if (diff > 0)
+ goto advloop;
+ }
+
+ /* Stop if high_key < low_key(rec). */
+ diff = cur->bc_ops->diff_two_keys(cur, &rec_key, high_key);
+ if (diff > 0)
+ break;
+
+ /* Callback */
+ error = fn(cur, recp, priv);
+ if (error < 0 || error == XFS_BTREE_QUERY_RANGE_ABORT)
+ break;
+
+advloop:
+ /* Move on to the next record. */
+ error = xfs_btree_increment(cur, 0, &stat);
+ if (error)
+ break;
+ }
+
+out:
+ return error;
+}
+
+/*
+ * Query an overlapped interval btree for all records overlapping a given
+ * interval. This function roughly follows the algorithm given in
+ * "Interval Trees" of _Introduction to Algorithms_, which is section
+ * 14.3 in the 2nd and 3rd editions.
+ *
+ * First, generate keys for the low and high records passed in.
+ *
+ * For any leaf node, generate the high and low keys for the record.
+ * If the record keys overlap with the query low/high keys, pass the
+ * record to the function iterator.
+ *
+ * For any internal node, compare the low and high keys of each
+ * pointer against the query low/high keys. If there's an overlap,
+ * follow the pointer.
+ *
+ * As an optimization, we stop scanning a block when we find a low key
+ * that is greater than the query's high key.
+ */
+STATIC int
+xfs_btree_overlapped_query_range(
+ struct xfs_btree_cur *cur,
+ union xfs_btree_key *low_key,
+ union xfs_btree_key *high_key,
+ xfs_btree_query_range_fn fn,
+ void *priv)
+{
+ union xfs_btree_ptr ptr;
+ union xfs_btree_ptr *pp;
+ union xfs_btree_key rec_key;
+ union xfs_btree_key rec_hkey;
+ union xfs_btree_key *lkp;
+ union xfs_btree_key *hkp;
+ union xfs_btree_rec *recp;
+ struct xfs_btree_block *block;
+ __int64_t ldiff;
+ __int64_t hdiff;
+ int level;
+ struct xfs_buf *bp;
+ int i;
+ int error;
+
+ /* Load the root of the btree. */
+ level = cur->bc_nlevels - 1;
+ cur->bc_ops->init_ptr_from_cur(cur, &ptr);
+ error = xfs_btree_lookup_get_block(cur, level, &ptr, &block);
+ if (error)
+ return error;
+ xfs_btree_get_block(cur, level, &bp);
+ trace_xfs_btree_overlapped_query_range(cur, level, bp);
+#ifdef DEBUG
+ error = xfs_btree_check_block(cur, block, level, bp);
+ if (error)
+ goto out;
+#endif
+ cur->bc_ptrs[level] = 1;
+
+ while (level < cur->bc_nlevels) {
+ block = xfs_btree_get_block(cur, level, &bp);
+
+ /* End of node, pop back towards the root. */
+ if (cur->bc_ptrs[level] > be16_to_cpu(block->bb_numrecs)) {
+pop_up:
+ if (level < cur->bc_nlevels - 1)
+ cur->bc_ptrs[level + 1]++;
+ level++;
+ continue;
+ }
+
+ if (level == 0) {
+ /* Handle a leaf node. */
+ recp = xfs_btree_rec_addr(cur, cur->bc_ptrs[0], block);
+
+ cur->bc_ops->init_high_key_from_rec(&rec_hkey, recp);
+ ldiff = cur->bc_ops->diff_two_keys(cur, &rec_hkey,
+ low_key);
+
+ cur->bc_ops->init_key_from_rec(&rec_key, recp);
+ hdiff = cur->bc_ops->diff_two_keys(cur, high_key,
+ &rec_key);
+
+ /*
+ * If (record's high key >= query's low key) and
+ * (query's high key >= record's low key), then
+ * this record overlaps the query range; callback.
+ */
+ if (ldiff >= 0 && hdiff >= 0) {
+ error = fn(cur, recp, priv);
+ if (error < 0 ||
+ error == XFS_BTREE_QUERY_RANGE_ABORT)
+ break;
+ } else if (hdiff < 0) {
+ /* Record is larger than high key; pop. */
+ goto pop_up;
+ }
+ cur->bc_ptrs[level]++;
+ continue;
+ }
+
+ /* Handle an internal node. */
+ lkp = xfs_btree_key_addr(cur, cur->bc_ptrs[level], block);
+ hkp = xfs_btree_high_key_addr(cur, cur->bc_ptrs[level], block);
+ pp = xfs_btree_ptr_addr(cur, cur->bc_ptrs[level], block);
+
+ ldiff = cur->bc_ops->diff_two_keys(cur, hkp, low_key);
+ hdiff = cur->bc_ops->diff_two_keys(cur, high_key, lkp);
+
+ /*
+ * If (pointer's high key >= query's low key) and
+ * (query's high key >= pointer's low key), then
+ * this record overlaps the query range; follow pointer.
+ */
+ if (ldiff >= 0 && hdiff >= 0) {
+ level--;
+ error = xfs_btree_lookup_get_block(cur, level, pp,
+ &block);
+ if (error)
+ goto out;
+ xfs_btree_get_block(cur, level, &bp);
+ trace_xfs_btree_overlapped_query_range(cur, level, bp);
+#ifdef DEBUG
+ error = xfs_btree_check_block(cur, block, level, bp);
+ if (error)
+ goto out;
+#endif
+ cur->bc_ptrs[level] = 1;
+ continue;
+ } else if (hdiff < 0) {
+ /* The low key is larger than the upper range; pop. */
+ goto pop_up;
+ }
+ cur->bc_ptrs[level]++;
+ }
+
+out:
+ /*
+ * If we don't end this function with the cursor pointing at a record
+ * block, a subsequent non-error cursor deletion will not release
+ * node-level buffers, causing a buffer leak. This is quite possible
+ * with a zero-results range query, so release the buffers if we
+ * failed to return any results.
+ */
+ if (cur->bc_bufs[0] == NULL) {
+ for (i = 0; i < cur->bc_nlevels; i++) {
+ if (cur->bc_bufs[i]) {
+ xfs_trans_brelse(cur->bc_tp, cur->bc_bufs[i]);
+ cur->bc_bufs[i] = NULL;
+ cur->bc_ptrs[i] = 0;
+ cur->bc_ra[i] = 0;
+ }
+ }
+ }
+
+ return error;
+}
+
+/*
+ * Query a btree for all records overlapping a given interval of keys. The
+ * supplied function will be called with each record found; return one of the
+ * XFS_BTREE_QUERY_RANGE_{CONTINUE,ABORT} values or the usual negative error
+ * code. This function returns XFS_BTREE_QUERY_RANGE_ABORT, zero, or a
+ * negative error code.
+ */
+int
+xfs_btree_query_range(
+ struct xfs_btree_cur *cur,
+ union xfs_btree_irec *low_rec,
+ union xfs_btree_irec *high_rec,
+ xfs_btree_query_range_fn fn,
+ void *priv)
+{
+ union xfs_btree_rec rec;
+ union xfs_btree_key low_key;
+ union xfs_btree_key high_key;
+
+ /* Find the keys of both ends of the interval. */
+ cur->bc_rec = *high_rec;
+ cur->bc_ops->init_rec_from_cur(cur, &rec);
+ cur->bc_ops->init_key_from_rec(&high_key, &rec);
+
+ cur->bc_rec = *low_rec;
+ cur->bc_ops->init_rec_from_cur(cur, &rec);
+ cur->bc_ops->init_key_from_rec(&low_key, &rec);
+
+ /* Enforce low key < high key. */
+ if (cur->bc_ops->diff_two_keys(cur, &low_key, &high_key) > 0)
+ return -EINVAL;
+
+ if (!(cur->bc_flags & XFS_BTREE_OVERLAPPING))
+ return xfs_btree_simple_query_range(cur, &low_key,
+ &high_key, fn, priv);
+ return xfs_btree_overlapped_query_range(cur, &low_key, &high_key,
+ fn, priv);
+}
diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
index 3645d91..4b1c04c 100644
--- a/fs/xfs/libxfs/xfs_btree.h
+++ b/fs/xfs/libxfs/xfs_btree.h
@@ -227,6 +227,12 @@ struct xfs_btree_ops {
#define LASTREC_DELREC 2
+union xfs_btree_irec {
+ struct xfs_alloc_rec_incore a;
+ struct xfs_bmbt_irec b;
+ struct xfs_inobt_rec_incore i;
+};
+
/*
* Btree cursor structure.
* This collects all information needed by the btree code in one place.
@@ -237,11 +243,7 @@ typedef struct xfs_btree_cur
struct xfs_mount *bc_mp; /* file system mount struct */
const struct xfs_btree_ops *bc_ops;
uint bc_flags; /* btree features - below */
- union {
- xfs_alloc_rec_incore_t a;
- xfs_bmbt_irec_t b;
- xfs_inobt_rec_incore_t i;
- } bc_rec; /* current insert/search record value */
+ union xfs_btree_irec bc_rec; /* current insert/search record value */
struct xfs_buf *bc_bufs[XFS_BTREE_MAXLEVELS]; /* buf ptr per level */
int bc_ptrs[XFS_BTREE_MAXLEVELS]; /* key/record # */
__uint8_t bc_ra[XFS_BTREE_MAXLEVELS]; /* readahead bits */
@@ -524,4 +526,14 @@ void xfs_btree_get_node_keys_overlapped(struct xfs_btree_cur *cur,
struct xfs_btree_block *block, union xfs_btree_key *key);
int xfs_btree_update_keys_overlapped(struct xfs_btree_cur *cur, int level);
+/* return codes */
+#define XFS_BTREE_QUERY_RANGE_CONTINUE 0 /* keep iterating */
+#define XFS_BTREE_QUERY_RANGE_ABORT 1 /* stop iterating */
+typedef int (*xfs_btree_query_range_fn)(struct xfs_btree_cur *cur,
+ union xfs_btree_rec *rec, void *priv);
+
+int xfs_btree_query_range(struct xfs_btree_cur *cur,
+ union xfs_btree_irec *low_rec, union xfs_btree_irec *high_rec,
+ xfs_btree_query_range_fn fn, void *priv);
+
#endif /* __XFS_BTREE_H__ */
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index 8fb59e6..a586268 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -2220,6 +2220,7 @@ DEFINE_EVENT(xfs_btree_cur_class, name, \
TP_PROTO(struct xfs_btree_cur *cur, int level, struct xfs_buf *bp), \
TP_ARGS(cur, level, bp))
DEFINE_BTREE_CUR_EVENT(xfs_btree_updkeys);
+DEFINE_BTREE_CUR_EVENT(xfs_btree_overlapped_query_range);
#endif /* _TRACE_XFS_H */
--
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