Merge tag 'for-6.7/block-2023-10-30' of git://git.kernel.dk/linux

Pull block updates from Jens Axboe:

 - Improvements to the queue_rqs() support, and adding null_blk support
   for that as well (Chengming)

 - Series improving badblocks support (Coly)

 - Key store support for sed-opal (Greg)

 - IBM partition string handling improvements (Jan)

 - Make number of ublk devices supported configurable (Mike)

 - Cancelation improvements for ublk (Ming)

 - MD pull requests via Song:
     - Handle timeout in md-cluster, by Denis Plotnikov
     - Cleanup pers->prepare_suspend, by Yu Kuai
     - Rewrite mddev_suspend(), by Yu Kuai
     - Simplify md_seq_ops, by Yu Kuai
     - Reduce unnecessary locking array_state_store(), by Mariusz
       Tkaczyk
     - Make rdev add/remove independent from daemon thread, by Yu Kuai
     - Refactor code around quiesce() and mddev_suspend(), by Yu Kuai

 - NVMe pull request via Keith:
     - nvme-auth updates (Mark)
     - nvme-tcp tls (Hannes)
     - nvme-fc annotaions (Kees)

 - Misc cleanups and improvements (Jiapeng, Joel)

* tag 'for-6.7/block-2023-10-30' of git://git.kernel.dk/linux: (95 commits)
  block: ublk_drv: Remove unused function
  md: cleanup pers->prepare_suspend()
  nvme-auth: allow mixing of secret and hash lengths
  nvme-auth: use transformed key size to create resp
  nvme-auth: alloc nvme_dhchap_key as single buffer
  nvmet-tcp: use 'spin_lock_bh' for state_lock()
  powerpc/pseries: PLPKS SED Opal keystore support
  block: sed-opal: keystore access for SED Opal keys
  block:sed-opal: SED Opal keystore
  ublk: simplify aborting request
  ublk: replace monitor with cancelable uring_cmd
  ublk: quiesce request queue when aborting queue
  ublk: rename mm_lock as lock
  ublk: move ublk_cancel_dev() out of ub->mutex
  ublk: make sure io cmd handled in submitter task context
  ublk: don't get ublk device reference in ublk_abort_queue()
  ublk: Make ublks_max configurable
  ublk: Limit dev_id/ub_number values
  md-cluster: check for timeout while a new disk adding
  nvme: rework NVME_AUTH Kconfig selection
  ...

8 files changed, 1465 insertions, 384 deletions

diff --git a/block/Kconfig b/block/Kconfig
index f1364d1c0d93..55ae2286a4de 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -186,6 +186,7 @@ config BLK_SED_OPAL
 	bool "Logic for interfacing with Opal enabled SEDs"
 	depends on KEYS
 	select PSERIES_PLPKS if PPC_PSERIES
+	select PSERIES_PLPKS_SED if PPC_PSERIES
 	help
 	Builds Logic for interfacing with Opal enabled controllers.
 	Enabling this option enables users to setup/unlock/lock
diff --git a/block/badblocks.c b/block/badblocks.c
index 3afb550c0f7b..fc92d4e18aa3 100644
--- a/block/badblocks.c
+++ b/block/badblocks.c
@@ -16,119 +16,830 @@
 #include <linux/types.h>
 #include <linux/slab.h>
 
-/**
- * badblocks_check() - check a given range for bad sectors
- * @bb:		the badblocks structure that holds all badblock information
- * @s:		sector (start) at which to check for badblocks
- * @sectors:	number of sectors to check for badblocks
- * @first_bad:	pointer to store location of the first badblock
- * @bad_sectors: pointer to store number of badblocks after @first_bad
+/*
+ * The purpose of badblocks set/clear is to manage bad blocks ranges which are
+ * identified by LBA addresses.
  *
- * We can record which blocks on each device are 'bad' and so just
- * fail those blocks, or that stripe, rather than the whole device.
- * Entries in the bad-block table are 64bits wide.  This comprises:
- * Length of bad-range, in sectors: 0-511 for lengths 1-512
- * Start of bad-range, sector offset, 54 bits (allows 8 exbibytes)
- *  A 'shift' can be set so that larger blocks are tracked and
- *  consequently larger devices can be covered.
- * 'Acknowledged' flag - 1 bit. - the most significant bit.
+ * When the caller of badblocks_set() wants to set a range of bad blocks, the
+ * setting range can be acked or unacked. And the setting range may merge,
+ * overwrite, skip the overlapped already set range, depends on who they are
+ * overlapped or adjacent, and the acknowledgment type of the ranges. It can be
+ * more complicated when the setting range covers multiple already set bad block
+ * ranges, with restrictions of maximum length of each bad range and the bad
+ * table space limitation.
  *
- * Locking of the bad-block table uses a seqlock so badblocks_check
- * might need to retry if it is very unlucky.
- * We will sometimes want to check for bad blocks in a bi_end_io function,
- * so we use the write_seqlock_irq variant.
+ * It is difficult and unnecessary to take care of all the possible situations,
+ * for setting a large range of bad blocks, we can handle it by dividing the
+ * large range into smaller ones when encounter overlap, max range length or
+ * bad table full conditions. Every time only a smaller piece of the bad range
+ * is handled with a limited number of conditions how it is interacted with
+ * possible overlapped or adjacent already set bad block ranges. Then the hard
+ * complicated problem can be much simpler to handle in proper way.
  *
- * When looking for a bad block we specify a range and want to
- * know if any block in the range is bad.  So we binary-search
- * to the last range that starts at-or-before the given endpoint,
- * (or "before the sector after the target range")
- * then see if it ends after the given start.
+ * When setting a range of bad blocks to the bad table, the simplified situations
+ * to be considered are, (The already set bad blocks ranges are naming with
+ *  prefix E, and the setting bad blocks range is naming with prefix S)
  *
- * Return:
- *  0: there are no known bad blocks in the range
- *  1: there are known bad block which are all acknowledged
- * -1: there are bad blocks which have not yet been acknowledged in metadata.
- * plus the start/length of the first bad section we overlap.
+ * 1) A setting range is not overlapped or adjacent to any other already set bad
+ *    block range.
+ *                         +--------+
+ *                         |    S   |
+ *                         +--------+
+ *        +-------------+               +-------------+
+ *        |      E1     |               |      E2     |
+ *        +-------------+               +-------------+
+ *    For this situation if the bad blocks table is not full, just allocate a
+ *    free slot from the bad blocks table to mark the setting range S. The
+ *    result is,
+ *        +-------------+  +--------+   +-------------+
+ *        |      E1     |  |    S   |   |      E2     |
+ *        +-------------+  +--------+   +-------------+
+ * 2) A setting range starts exactly at a start LBA of an already set bad blocks
+ *    range.
+ * 2.1) The setting range size < already set range size
+ *        +--------+
+ *        |    S   |
+ *        +--------+
+ *        +-------------+
+ *        |      E      |
+ *        +-------------+
+ * 2.1.1) If S and E are both acked or unacked range, the setting range S can
+ *    be merged into existing bad range E. The result is,
+ *        +-------------+
+ *        |      S      |
+ *        +-------------+
+ * 2.1.2) If S is unacked setting and E is acked, the setting will be denied, and
+ *    the result is,
+ *        +-------------+
+ *        |      E      |
+ *        +-------------+
+ * 2.1.3) If S is acked setting and E is unacked, range S can overwrite on E.
+ *    An extra slot from the bad blocks table will be allocated for S, and head
+ *    of E will move to end of the inserted range S. The result is,
+ *        +--------+----+
+ *        |    S   | E  |
+ *        +--------+----+
+ * 2.2) The setting range size == already set range size
+ * 2.2.1) If S and E are both acked or unacked range, the setting range S can
+ *    be merged into existing bad range E. The result is,
+ *        +-------------+
+ *        |      S      |
+ *        +-------------+
+ * 2.2.2) If S is unacked setting and E is acked, the setting will be denied, and
+ *    the result is,
+ *        +-------------+
+ *        |      E      |
+ *        +-------------+
+ * 2.2.3) If S is acked setting and E is unacked, range S can overwrite all of
+      bad blocks range E. The result is,
+ *        +-------------+
+ *        |      S      |
+ *        +-------------+
+ * 2.3) The setting range size > already set range size
+ *        +-------------------+
+ *        |          S        |
+ *        +-------------------+
+ *        +-------------+
+ *        |      E      |
+ *        +-------------+
+ *    For such situation, the setting range S can be treated as two parts, the
+ *    first part (S1) is as same size as the already set range E, the second
+ *    part (S2) is the rest of setting range.
+ *        +-------------+-----+        +-------------+       +-----+
+ *        |    S1       | S2  |        |     S1      |       | S2  |
+ *        +-------------+-----+  ===>  +-------------+       +-----+
+ *        +-------------+              +-------------+
+ *        |      E      |              |      E      |
+ *        +-------------+              +-------------+
+ *    Now we only focus on how to handle the setting range S1 and already set
+ *    range E, which are already explained in 2.2), for the rest S2 it will be
+ *    handled later in next loop.
+ * 3) A setting range starts before the start LBA of an already set bad blocks
+ *    range.
+ *        +-------------+
+ *        |      S      |
+ *        +-------------+
+ *             +-------------+
+ *             |      E      |
+ *             +-------------+
+ *    For this situation, the setting range S can be divided into two parts, the
+ *    first (S1) ends at the start LBA of already set range E, the second part
+ *    (S2) starts exactly at a start LBA of the already set range E.
+ *        +----+---------+             +----+      +---------+
+ *        | S1 |    S2   |             | S1 |      |    S2   |
+ *        +----+---------+      ===>   +----+      +---------+
+ *             +-------------+                     +-------------+
+ *             |      E      |                     |      E      |
+ *             +-------------+                     +-------------+
+ *    Now only the first part S1 should be handled in this loop, which is in
+ *    similar condition as 1). The rest part S2 has exact same start LBA address
+ *    of the already set range E, they will be handled in next loop in one of
+ *    situations in 2).
+ * 4) A setting range starts after the start LBA of an already set bad blocks
+ *    range.
+ * 4.1) If the setting range S exactly matches the tail part of already set bad
+ *    blocks range E, like the following chart shows,
+ *            +---------+
+ *            |   S     |
+ *            +---------+
+ *        +-------------+
+ *        |      E      |
+ *        +-------------+
+ * 4.1.1) If range S and E have same acknowledge value (both acked or unacked),
+ *    they will be merged into one, the result is,
+ *        +-------------+
+ *        |      S      |
+ *        +-------------+
+ * 4.1.2) If range E is acked and the setting range S is unacked, the setting
+ *    request of S will be rejected, the result is,
+ *        +-------------+
+ *        |      E      |
+ *        +-------------+
+ * 4.1.3) If range E is unacked, and the setting range S is acked, then S may
+ *    overwrite the overlapped range of E, the result is,
+ *        +---+---------+
+ *        | E |    S    |
+ *        +---+---------+
+ * 4.2) If the setting range S stays in middle of an already set range E, like
+ *    the following chart shows,
+ *             +----+
+ *             | S  |
+ *             +----+
+ *        +--------------+
+ *        |       E      |
+ *        +--------------+
+ * 4.2.1) If range S and E have same acknowledge value (both acked or unacked),
+ *    they will be merged into one, the result is,
+ *        +--------------+
+ *        |       S      |
+ *        +--------------+
+ * 4.2.2) If range E is acked and the setting range S is unacked, the setting
+ *    request of S will be rejected, the result is also,
+ *        +--------------+
+ *        |       E      |
+ *        +--------------+
+ * 4.2.3) If range E is unacked, and the setting range S is acked, then S will
+ *    inserted into middle of E and split previous range E into two parts (E1
+ *    and E2), the result is,
+ *        +----+----+----+
+ *        | E1 |  S | E2 |
+ *        +----+----+----+
+ * 4.3) If the setting bad blocks range S is overlapped with an already set bad
+ *    blocks range E. The range S starts after the start LBA of range E, and
+ *    ends after the end LBA of range E, as the following chart shows,
+ *            +-------------------+
+ *            |          S        |
+ *            +-------------------+
+ *        +-------------+
+ *        |      E      |
+ *        +-------------+
+ *    For this situation the range S can be divided into two parts, the first
+ *    part (S1) ends at end range E, and the second part (S2) has rest range of
+ *    origin S.
+ *            +---------+---------+            +---------+      +---------+
+ *            |    S1   |    S2   |            |    S1   |      |    S2   |
+ *            +---------+---------+  ===>      +---------+      +---------+
+ *        +-------------+                  +-------------+
+ *        |      E      |                  |      E      |
+ *        +-------------+                  +-------------+
+ *     Now in this loop the setting range S1 and already set range E can be
+ *     handled as the situations 4.1), the rest range S2 will be handled in next
+ *     loop and ignored in this loop.
+ * 5) A setting bad blocks range S is adjacent to one or more already set bad
+ *    blocks range(s), and they are all acked or unacked range.
+ * 5.1) Front merge: If the already set bad blocks range E is before setting
+ *    range S and they are adjacent,
+ *                +------+
+ *                |  S   |
+ *                +------+
+ *        +-------+
+ *        |   E   |
+ *        +-------+
+ * 5.1.1) When total size of range S and E <= BB_MAX_LEN, and their acknowledge
+ *    values are same, the setting range S can front merges into range E. The
+ *    result is,
+ *        +--------------+
+ *        |       S      |
+ *        +--------------+
+ * 5.1.2) Otherwise these two ranges cannot merge, just insert the setting
+ *    range S right after already set range E into the bad blocks table. The
+ *    result is,
+ *        +--------+------+
+ *        |   E    |   S  |
+ *        +--------+------+
+ * 6) Special cases which above conditions cannot handle
+ * 6.1) Multiple already set ranges may merge into less ones in a full bad table
+ *        +-------------------------------------------------------+
+ *        |                           S                           |
+ *        +-------------------------------------------------------+
+ *        |<----- BB_MAX_LEN ----->|
+ *                                 +-----+     +-----+   +-----+
+ *                                 | E1  |     | E2  |   | E3  |
+ *                                 +-----+     +-----+   +-----+
+ *     In the above example, when the bad blocks table is full, inserting the
+ *     first part of setting range S will fail because no more available slot
+ *     can be allocated from bad blocks table. In this situation a proper
+ *     setting method should be go though all the setting bad blocks range and
+ *     look for chance to merge already set ranges into less ones. When there
+ *     is available slot from bad blocks table, re-try again to handle more
+ *     setting bad blocks ranges as many as possible.
+ *        +------------------------+
+ *        |          S3            |
+ *        +------------------------+
+ *        |<----- BB_MAX_LEN ----->|
+ *                                 +-----+-----+-----+---+-----+--+
+ *                                 |       S1        |     S2     |
+ *                                 +-----+-----+-----+---+-----+--+
+ *     The above chart shows although the first part (S3) cannot be inserted due
+ *     to no-space in bad blocks table, but the following E1, E2 and E3 ranges
+ *     can be merged with rest part of S into less range S1 and S2. Now there is
+ *     1 free slot in bad blocks table.
+ *        +------------------------+-----+-----+-----+---+-----+--+
+ *        |           S3           |       S1        |     S2     |
+ *        +------------------------+-----+-----+-----+---+-----+--+
+ *     Since the bad blocks table is not full anymore, re-try again for the
+ *     origin setting range S. Now the setting range S3 can be inserted into the
+ *     bad blocks table with previous freed slot from multiple ranges merge.
+ * 6.2) Front merge after overwrite
+ *    In the following example, in bad blocks table, E1 is an acked bad blocks
+ *    range and E2 is an unacked bad blocks range, therefore they are not able
+ *    to merge into a larger range. The setting bad blocks range S is acked,
+ *    therefore part of E2 can be overwritten by S.
+ *                      +--------+
+ *                      |    S   |                             acknowledged
+ *                      +--------+                         S:       1
+ *              +-------+-------------+                   E1:       1
+ *              |   E1  |    E2       |                   E2:       0
+ *              +-------+-------------+
+ *     With previous simplified routines, after overwriting part of E2 with S,
+ *     the bad blocks table should be (E3 is remaining part of E2 which is not
+ *     overwritten by S),
+ *                                                             acknowledged
+ *              +-------+--------+----+                    S:       1
+ *              |   E1  |    S   | E3 |                   E1:       1
+ *              +-------+--------+----+                   E3:       0
+ *     The above result is correct but not perfect. Range E1 and S in the bad
+ *     blocks table are all acked, merging them into a larger one range may
+ *     occupy less bad blocks table space and make badblocks_check() faster.
+ *     Therefore in such situation, after overwriting range S, the previous range
+ *     E1 should be checked for possible front combination. Then the ideal
+ *     result can be,
+ *              +----------------+----+                        acknowledged
+ *              |       E1       | E3 |                   E1:       1
+ *              +----------------+----+                   E3:       0
+ * 6.3) Behind merge: If the already set bad blocks range E is behind the setting
+ *    range S and they are adjacent. Normally we don't need to care about this
+ *    because front merge handles this while going though range S from head to
+ *    tail, except for the tail part of range S. When the setting range S are
+ *    fully handled, all the above simplified routine doesn't check whether the
+ *    tail LBA of range S is adjacent to the next already set range and not
+ *    merge them even it is possible.
+ *        +------+
+ *        |  S   |
+ *        +------+
+ *               +-------+
+ *               |   E   |
+ *               +-------+
+ *    For the above special situation, when the setting range S are all handled
+ *    and the loop ends, an extra check is necessary for whether next already
+ *    set range E is right after S and mergeable.
+ * 6.3.1) When total size of range E and S <= BB_MAX_LEN, and their acknowledge
+ *    values are same, the setting range S can behind merges into range E. The
+ *    result is,
+ *        +--------------+
+ *        |       S      |
+ *        +--------------+
+ * 6.3.2) Otherwise these two ranges cannot merge, just insert the setting range
+ *     S in front of the already set range E in the bad blocks table. The result
+ *     is,
+ *        +------+-------+
+ *        |  S   |   E   |
+ *        +------+-------+
+ *
+ * All the above 5 simplified situations and 3 special cases may cover 99%+ of
+ * the bad block range setting conditions. Maybe there is some rare corner case
+ * is not considered and optimized, it won't hurt if badblocks_set() fails due
+ * to no space, or some ranges are not merged to save bad blocks table space.
+ *
+ * Inside badblocks_set() each loop starts by jumping to re_insert label, every
+ * time for the new loop prev_badblocks() is called to find an already set range
+ * which starts before or at current setting range. Since the setting bad blocks
+ * range is handled from head to tail, most of the cases it is unnecessary to do
+ * the binary search inside prev_badblocks(), it is possible to provide a hint
+ * to prev_badblocks() for a fast path, then the expensive binary search can be
+ * avoided. In my test with the hint to prev_badblocks(), except for the first
+ * loop, all rested calls to prev_badblocks() can go into the fast path and
+ * return correct bad blocks table index immediately.
+ *
+ *
+ * Clearing a bad blocks range from the bad block table has similar idea as
+ * setting does, but much more simpler. The only thing needs to be noticed is
+ * when the clearing range hits middle of a bad block range, the existing bad
+ * block range will split into two, and one more item should be added into the
+ * bad block table. The simplified situations to be considered are, (The already
+ * set bad blocks ranges in bad block table are naming with prefix E, and the
+ * clearing bad blocks range is naming with prefix C)
+ *
+ * 1) A clearing range is not overlapped to any already set ranges in bad block
+ *    table.
+ *    +-----+         |          +-----+         |          +-----+
+ *    |  C  |         |          |  C  |         |          |  C  |
+ *    +-----+         or         +-----+         or         +-----+
+ *            +---+   |   +----+         +----+  |  +---+
+ *            | E |   |   | E1 |         | E2 |  |  | E |
+ *            +---+   |   +----+         +----+  |  +---+
+ *    For the above situations, no bad block to be cleared and no failure
+ *    happens, simply returns 0.
+ * 2) The clearing range hits middle of an already setting bad blocks range in
+ *    the bad block table.
+ *            +---+
+ *            | C |
+ *            +---+
+ *     +-----------------+
+ *     |         E       |
+ *     +-----------------+
+ *    In this situation if the bad block table is not full, the range E will be
+ *    split into two ranges E1 and E2. The result is,
+ *     +------+   +------+
+ *     |  E1  |   |  E2  |
+ *     +------+   +------+
+ * 3) The clearing range starts exactly at same LBA as an already set bad block range
+ *    from the bad block table.
+ * 3.1) Partially covered at head part
+ *         +------------+
+ *         |     C      |
+ *         +------------+
+ *         +-----------------+
+ *         |         E       |
+ *         +-----------------+
+ *    For this situation, the overlapped already set range will update the
+ *    start LBA to end of C and shrink the range to BB_LEN(E) - BB_LEN(C). No
+ *    item deleted from bad block table. The result is,
+ *                      +----+
+ *                      | E1 |
+ *                      +----+
+ * 3.2) Exact fully covered
+ *         +-----------------+
+ *         |         C       |
+ *         +-----------------+
+ *         +-----------------+
+ *         |         E       |
+ *         +-----------------+
+ *    For this situation the whole bad blocks range E will be cleared and its
+ *    corresponded item is deleted from the bad block table.
+ * 4) The clearing range exactly ends at same LBA as an already set bad block
+ *    range.
+ *                   +-------+
+ *                   |   C   |
+ *                   +-------+
+ *         +-----------------+
+ *         |         E       |
+ *         +-----------------+
+ *    For the above situation, the already set range E is updated to shrink its
+ *    end to the start of C, and reduce its length to BB_LEN(E) - BB_LEN(C).
+ *    The result is,
+ *         +---------+
+ *         |    E    |
+ *         +---------+
+ * 5) The clearing range is partially overlapped with an already set bad block
+ *    range from the bad block table.
+ * 5.1) The already set bad block range is front overlapped with the clearing
+ *    range.
+ *         +----------+
+ *         |     C    |
+ *         +----------+
+ *              +------------+
+ *              |      E     |
+ *              +------------+
+ *   For such situation, the clearing range C can be treated as two parts. The
+ *   first part ends at the start LBA of range E, and the second part starts at
+ *   same LBA of range E.
+ *         +----+-----+               +----+   +-----+
+ *         | C1 | C2  |               | C1 |   | C2  |
+ *         +----+-----+         ===>  +----+   +-----+
+ *              +------------+                 +------------+
+ *              |      E     |                 |      E     |
+ *              +------------+                 +------------+
+ *   Now the first part C1 can be handled as condition 1), and the second part C2 can be
+ *   handled as condition 3.1) in next loop.
+ * 5.2) The already set bad block range is behind overlaopped with the clearing
+ *   range.
+ *                 +----------+
+ *                 |     C    |
+ *                 +----------+
+ *         +------------+
+ *         |      E     |
+ *         +------------+
+ *   For such situation, the clearing range C can be treated as two parts. The
+ *   first part C1 ends at same end LBA of range E, and the second part starts
+ *   at end LBA of range E.
+ *                 +----+-----+                 +----+    +-----+
+ *                 | C1 | C2  |                 | C1 |    | C2  |
+ *                 +----+-----+  ===>           +----+    +-----+
+ *         +------------+               +------------+
+ *         |      E     |               |      E     |
+ *         +------------+               +------------+
+ *   Now the first part clearing range C1 can be handled as condition 4), and
+ *   the second part clearing range C2 can be handled as condition 1) in next
+ *   loop.
+ *
+ *   All bad blocks range clearing can be simplified into the above 5 situations
+ *   by only handling the head part of the clearing range in each run of the
+ *   while-loop. The idea is similar to bad blocks range setting but much
+ *   simpler.
  */
-int badblocks_check(struct badblocks *bb, sector_t s, int sectors,
-			sector_t *first_bad, int *bad_sectors)
+
+/*
+ * Find the range starts at-or-before 's' from bad table. The search
+ * starts from index 'hint' and stops at index 'hint_end' from the bad
+ * table.
+ */
+static int prev_by_hint(struct badblocks *bb, sector_t s, int hint)
 {
-	int hi;
-	int lo;
+	int hint_end = hint + 2;
 	u64 *p = bb->page;
-	int rv;
-	sector_t target = s + sectors;
-	unsigned seq;
+	int ret = -1;
 
-	if (bb->shift > 0) {
-		/* round the start down, and the end up */
-		s >>= bb->shift;
-		target += (1<<bb->shift) - 1;
-		target >>= bb->shift;
+	while ((hint < hint_end) && ((hint + 1) <= bb->count) &&
+	       (BB_OFFSET(p[hint]) <= s)) {
+		if ((hint + 1) == bb->count || BB_OFFSET(p[hint + 1]) > s) {
+			ret = hint;
+			break;
+		}
+		hint++;
+	}
+
+	return ret;
+}
+
+/*
+ * Find the range starts at-or-before bad->start. If 'hint' is provided
+ * (hint >= 0) then search in the bad table from hint firstly. It is
+ * very probably the wanted bad range can be found from the hint index,
+ * then the unnecessary while-loop iteration can be avoided.
+ */
+static int prev_badblocks(struct badblocks *bb, struct badblocks_context *bad,
+			  int hint)
+{
+	sector_t s = bad->start;
+	int ret = -1;
+	int lo, hi;
+	u64 *p;
+
+	if (!bb->count)
+		goto out;
+
+	if (hint >= 0) {
+		ret = prev_by_hint(bb, s, hint);
+		if (ret >= 0)
+			goto out;
 	}
-	/* 'target' is now the first block after the bad range */
 
-retry:
-	seq = read_seqbegin(&bb->lock);
 	lo = 0;
-	rv = 0;
 	hi = bb->count;
+	p = bb->page;
 
-	/* Binary search between lo and hi for 'target'
-	 * i.e. for the last range that starts before 'target'
-	 */
-	/* INVARIANT: ranges before 'lo' and at-or-after 'hi'
-	 * are known not to be the last range before target.
-	 * VARIANT: hi-lo is the number of possible
-	 * ranges, and decreases until it reaches 1
-	 */
+	/* The following bisect search might be unnecessary */
+	if (BB_OFFSET(p[lo]) > s)
+		return -1;
+	if (BB_OFFSET(p[hi - 1]) <= s)
+		return hi - 1;
+
+	/* Do bisect search in bad table */
 	while (hi - lo > 1) {
-		int mid = (lo + hi) / 2;
+		int mid = (lo + hi)/2;
 		sector_t a = BB_OFFSET(p[mid]);
 
-		if (a < target)
-			/* This could still be the one, earlier ranges
-			 * could not.
-			 */
+		if (a == s) {
+			ret = mid;
+			goto out;
+		}
+
+		if (a < s)
 			lo = mid;
 		else
-			/* This and later ranges are definitely out. */
 			hi = mid;
 	}
-	/* 'lo' might be the last that started before target, but 'hi' isn't */
-	if (hi > lo) {
-		/* need to check all range that end after 's' to see if
-		 * any are unacknowledged.
+
+	if (BB_OFFSET(p[lo]) <= s)
+		ret = lo;
+out:
+	return ret;
+}
+
+/*
+ * Return 'true' if the range indicated by 'bad' can be backward merged
+ * with the bad range (from the bad table) index by 'behind'.
+ */
+static bool can_merge_behind(struct badblocks *bb,
+			     struct badblocks_context *bad, int behind)
+{
+	sector_t sectors = bad->len;
+	sector_t s = bad->start;
+	u64 *p = bb->page;
+
+	if ((s < BB_OFFSET(p[behind])) &&
+	    ((s + sectors) >= BB_OFFSET(p[behind])) &&
+	    ((BB_END(p[behind]) - s) <= BB_MAX_LEN) &&
+	    BB_ACK(p[behind]) == bad->ack)
+		return true;
+	return false;
+}
+
+/*
+ * Do backward merge for range indicated by 'bad' and the bad range
+ * (from the bad table) indexed by 'behind'. The return value is merged
+ * sectors from bad->len.
+ */
+static int behind_merge(struct badblocks *bb, struct badblocks_context *bad,
+			int behind)
+{
+	sector_t sectors = bad->len;
+	sector_t s = bad->start;
+	u64 *p = bb->page;
+	int merged = 0;
+
+	WARN_ON(s >= BB_OFFSET(p[behind]));
+	WARN_ON((s + sectors) < BB_OFFSET(p[behind]));
+
+	if (s < BB_OFFSET(p[behind])) {
+		merged = BB_OFFSET(p[behind]) - s;
+		p[behind] =  BB_MAKE(s, BB_LEN(p[behind]) + merged, bad->ack);
+
+		WARN_ON((BB_LEN(p[behind]) + merged) >= BB_MAX_LEN);
+	}
+
+	return merged;
+}
+
+/*
+ * Return 'true' if the range indicated by 'bad' can be forward
+ * merged with the bad range (from the bad table) indexed by 'prev'.
+ */
+static bool can_merge_front(struct badblocks *bb, int prev,
+			    struct badblocks_context *bad)
+{
+	sector_t s = bad->start;
+	u64 *p = bb->page;
+
+	if (BB_ACK(p[prev]) == bad->ack &&
+	    (s < BB_END(p[prev]) ||
+	     (s == BB_END(p[prev]) && (BB_LEN(p[prev]) < BB_MAX_LEN))))
+		return true;
+	return false;
+}
+
+/*
+ * Do forward merge for range indicated by 'bad' and the bad range
+ * (from bad table) indexed by 'prev'. The return value is sectors
+ * merged from bad->len.
+ */
+static int front_merge(struct badblocks *bb, int prev, struct badblocks_context *bad)
+{
+	sector_t sectors = bad->len;
+	sector_t s = bad->start;
+	u64 *p = bb->page;
+	int merged = 0;
+
+	WARN_ON(s > BB_END(p[prev]));
+
+	if (s < BB_END(p[prev])) {
+		merged = min_t(sector_t, sectors, BB_END(p[prev]) - s);
+	} else {
+		merged = min_t(sector_t, sectors, BB_MAX_LEN - BB_LEN(p[prev]));
+		if ((prev + 1) < bb->count &&
+		    merged > (BB_OFFSET(p[prev + 1]) - BB_END(p[prev]))) {
+			merged = BB_OFFSET(p[prev + 1]) - BB_END(p[prev]);
+		}
+
+		p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
+				  BB_LEN(p[prev]) + merged, bad->ack);
+	}
+
+	return merged;
+}
+
+/*
+ * 'Combine' is a special case which can_merge_front() is not able to
+ * handle: If a bad range (indexed by 'prev' from bad table) exactly
+ * starts as bad->start, and the bad range ahead of 'prev' (indexed by
+ * 'prev - 1' from bad table) exactly ends at where 'prev' starts, and
+ * the sum of their lengths does not exceed BB_MAX_LEN limitation, then
+ * these two bad range (from bad table) can be combined.
+ *
+ * Return 'true' if bad ranges indexed by 'prev' and 'prev - 1' from bad
+ * table can be combined.
+ */
+static bool can_combine_front(struct badblocks *bb, int prev,
+			      struct badblocks_context *bad)
+{
+	u64 *p = bb->page;
+
+	if ((prev > 0) &&
+	    (BB_OFFSET(p[prev]) == bad->start) &&
+	    (BB_END(p[prev - 1]) == BB_OFFSET(p[prev])) &&
+	    (BB_LEN(p[prev - 1]) + BB_LEN(p[prev]) <= BB_MAX_LEN) &&
+	    (BB_ACK(p[prev - 1]) == BB_ACK(p[prev])))
+		return true;
+	return false;
+}
+
+/*
+ * Combine the bad ranges indexed by 'prev' and 'prev - 1' (from bad
+ * table) into one larger bad range, and the new range is indexed by
+ * 'prev - 1'.
+ * The caller of front_combine() will decrease bb->count, therefore
+ * it is unnecessary to clear p[perv] after front merge.
+ */
+static void front_combine(struct badblocks *bb, int prev)
+{
+	u64 *p = bb->page;
+
+	p[prev - 1] = BB_MAKE(BB_OFFSET(p[prev - 1]),
+			      BB_LEN(p[prev - 1]) + BB_LEN(p[prev]),
+			      BB_ACK(p[prev]));
+	if ((prev + 1) < bb->count)
+		memmove(p + prev, p + prev + 1, (bb->count - prev - 1) * 8);
+}
+
+/*
+ * Return 'true' if the range indicated by 'bad' is exactly forward
+ * overlapped with the bad range (from bad table) indexed by 'front'.
+ * Exactly forward overlap means the bad range (from bad table) indexed
+ * by 'prev' does not cover the whole range indicated by 'bad'.
+ */
+static bool overlap_front(struct badblocks *bb, int front,
+			  struct badblocks_context *bad)
+{
+	u64 *p = bb->page;
+
+	if (bad->start >= BB_OFFSET(p[front]) &&
+	    bad->start < BB_END(p[front]))
+		return true;
+	return false;
+}
+
+/*
+ * Return 'true' if the range indicated by 'bad' is exactly backward
+ * overlapped with the bad range (from bad table) indexed by 'behind'.
+ */
+static bool overlap_behind(struct badblocks *bb, struct badblocks_context *bad,
+			   int behind)
+{
+	u64 *p = bb->page;
+
+	if (bad->start < BB_OFFSET(p[behind]) &&
+	    (bad->start + bad->len) > BB_OFFSET(p[behind]))
+		return true;
+	return false;
+}
+
+/*
+ * Return 'true' if the range indicated by 'bad' can overwrite the bad
+ * range (from bad table) indexed by 'prev'.
+ *
+ * The range indicated by 'bad' can overwrite the bad range indexed by
+ * 'prev' when,
+ * 1) The whole range indicated by 'bad' can cover partial or whole bad
+ *    range (from bad table) indexed by 'prev'.
+ * 2) The ack value of 'bad' is larger or equal to the ack value of bad
+ *    range 'prev'.
+ *
+ * If the overwriting doesn't cover the whole bad range (from bad table)
+ * indexed by 'prev', new range might be split from existing bad range,
+ * 1) The overwrite covers head or tail part of existing bad range, 1
+ *    extra bad range will be split and added into the bad table.
+ * 2) The overwrite covers middle of existing bad range, 2 extra bad
+ *    ranges will be split (ahead and after the overwritten range) and
+ *    added into the bad table.
+ * The number of extra split ranges of the overwriting is stored in
+ * 'extra' and returned for the caller.
+ */
+static bool can_front_overwrite(struct badblocks *bb, int prev,
+				struct badblocks_context *bad, int *extra)
+{
+	u64 *p = bb->page;
+	int len;
+
+	WARN_ON(!overlap_front(bb, prev, bad));
+
+	if (BB_ACK(p[prev]) >= bad->ack)
+		return false;
+
+	if (BB_END(p[prev]) <= (bad->start + bad->len)) {
+		len = BB_END(p[prev]) - bad->start;
+		if (BB_OFFSET(p[prev]) == bad->start)
+			*extra = 0;
+		else
+			*extra = 1;
+
+		bad->len = len;