Re: [PATCH v7 2/6] badblocks: add helper routines for badblock ranges handling

Xiao Ni
2023-09-02T14:22:50Z

On Sat, Aug 12, 2023 at 1:07 AM Coly Li <colyli@suse.de> wrote:
>
> This patch adds several helper routines to improve badblock ranges
> handling. These helper routines will be used later in the improved
> version of badblocks_set()/badblocks_clear()/badblocks_check().
>
> - Helpers prev_by_hint() and prev_badblocks() are used to find the bad
> range from bad table which the searching range starts at or after.
>
> - The following helpers are to decide the relative layout between the
> manipulating range and existing bad block range from bad table.
> - can_merge_behind()
> Return 'true' if the manipulating range can backward merge with the
> bad block range.
> - can_merge_front()
> Return 'true' if the manipulating range can forward merge with the
> bad block range.
> - can_combine_front()
> Return 'true' if two adjacent bad block ranges before the
> manipulating range can be merged.
> - overlap_front()
> Return 'true' if the manipulating range exactly overlaps with the
> bad block range in front of its range.
> - overlap_behind()
> Return 'true' if the manipulating range exactly overlaps with the
> bad block range behind its range.
> - can_front_overwrite()
> Return 'true' if the manipulating range can forward overwrite the
> bad block range in front of its range.
>
> - The following helpers are to add the manipulating range into the bad
> block table. Different routine is called with the specific relative
> layout between the manipulating range and other bad block range in the
> bad block table.
> - behind_merge()
> Merge the manipulating range with the bad block range behind its
> range, and return the number of merged length in unit of sector.
> - front_merge()
> Merge the manipulating range with the bad block range in front of
> its range, and return the number of merged length in unit of sector.
> - front_combine()
> Combine the two adjacent bad block ranges before the manipulating
> range into a larger one.
> - front_overwrite()
> Overwrite partial of whole bad block range which is in front of the
> manipulating range. The overwrite may split existing bad block range
> and generate more bad block ranges into the bad block table.
> - insert_at()
> Insert the manipulating range at a specific location in the bad
> block table.
>
> All the above helpers are used in later patches to improve the bad block
> ranges handling for badblocks_set()/badblocks_clear()/badblocks_check().
>
> Signed-off-by: Coly Li <colyli@suse.de>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Geliang Tang <geliang.tang@suse.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: NeilBrown <neilb@suse.de>
> Cc: Vishal L Verma <vishal.l.verma@intel.com>
> Cc: Xiao Ni <xni@redhat.com>
> ---
> block/badblocks.c | 386 ++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 386 insertions(+)
>
> diff --git a/block/badblocks.c b/block/badblocks.c
> index 3afb550c0f7b..7e7f9f14bb1d 100644
> --- a/block/badblocks.c
> +++ b/block/badblocks.c
> @@ -16,6 +16,392 @@
> #include <linux/types.h>
> #include <linux/slab.h>
>
> +/*
> + * 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 hint_end = hint + 2;
> + u64 *p = bb->page;
> + int ret = -1;
> +
> + 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;
> + }
> +
> + lo = 0;
> + hi = bb->count;
> + p = bb->page;
> +
> + /* 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;
> + sector_t a = BB_OFFSET(p[mid]);
> +
> + if (a == s) {
> + ret = mid;
> + goto out;
> + }
> +
> + if (a < s)
> + lo = mid;
> + else
> + hi = mid;
> + }
> +
> + 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.

Hi Coly

A typo error: s/perv/prev/g

> + */
> +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;

The comments say it can do overwrite when the bad's ack and prev's ack
are equal. But it returns false when the acks are equal. So there is a
conflict between the codes and comments. The codes are good for me.
Maybe we need to modify the comments?

> +
> + 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;
> + } else {
> + if (BB_OFFSET(p[prev]) == bad->start)
> + *extra = 1;
> + else
> + /*
> + * prev range will be split into two, beside the overwritten
> + * one, an extra slot needed from bad table.
> + */
> + *extra = 2;
> + }
> +
> + if ((bb->count + (*extra)) >= MAX_BADBLOCKS)
> + return false;
> +
> + return true;
> +}
> +
> +/*
> + * Do the overwrite from the range indicated by 'bad' to the bad range
> + * (from bad table) indexed by 'prev'.
> + * The previously called can_front_overwrite() will provide how many
> + * extra bad range(s) might be split and added into the bad table. All
> + * the splitting cases in the bad table will be handled here.
> + */
> +static int front_overwrite(struct badblocks *bb, int prev,
> + struct badblocks_context *bad, int extra)
> +{
> + u64 *p = bb->page;
> + sector_t orig_end = BB_END(p[prev]);
> + int orig_ack = BB_ACK(p[prev]);
> +
> + switch (extra) {
> + case 0:
> + p[prev] = BB_MAKE(BB_OFFSET(p[prev]), BB_LEN(p[prev]),
> + bad->ack);
> + break;
> + case 1:
> + if (BB_OFFSET(p[prev]) == bad->start) {
> + p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
> + bad->len, bad->ack);
> + memmove(p + prev + 2, p + prev + 1,
> + (bb->count - prev - 1) * 8);
> + p[prev + 1] = BB_MAKE(bad->start + bad->len,
> + orig_end - BB_END(p[prev]),
> + orig_ack);
> + } else {
> + p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
> + bad->start - BB_OFFSET(p[prev]),
> + orig_ack);
> + /*
> + * prev +2 -> prev + 1 + 1, which is for,
> + * 1) prev + 1: the slot index of the previous one
> + * 2) + 1: one more slot for extra being 1.
> + */
> + memmove(p + prev + 2, p + prev + 1,
> + (bb->count - prev - 1) * 8);
> + p[prev + 1] = BB_MAKE(bad->start, bad->len, bad->ack);
> + }
> + break;
> + case 2:
> + p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
> + bad->start - BB_OFFSET(p[prev]),
> + orig_ack);
> + /*
> + * prev + 3 -> prev + 1 + 2, which is for,
> + * 1) prev + 1: the slot index of the previous one
> + * 2) + 2: two more slots for extra being 2.
> + */
> + memmove(p + prev + 3, p + prev + 1,
> + (bb->count - prev - 1) * 8);
> + p[prev + 1] = BB_MAKE(bad->start, bad->len, bad->ack);
> + p[prev + 2] = BB_MAKE(BB_END(p[prev + 1]),
> + orig_end - BB_END(p[prev + 1]),
> + orig_ack);
> + break;
> + default:
> + break;
> + }
> +
> + return bad->len;
> +}
> +
> +/*
> + * Explicitly insert a range indicated by 'bad' to the bad table, where
> + * the location is indexed by 'at'.
> + */
> +static int insert_at(struct badblocks *bb, int at, struct badblocks_context *bad)
> +{
> + u64 *p = bb->page;
> + int len;
> +
> + WARN_ON(badblocks_full(bb));
> +
> + len = min_t(sector_t, bad->len, BB_MAX_LEN);
> + if (at < bb->count)
> + memmove(p + at + 1, p + at, (bb->count - at) * 8);
> + p[at] = BB_MAKE(bad->start, len, bad->ack);
> +
> + return len;
> +}
> +
> /**
> * badblocks_check() - check a given range for bad sectors
> * @bb: the badblocks structure that holds all badblock information
> --
> 2.35.3
>

There are only two places that are not important. One is a typo error
and the other is a question about the comments. This patch is good for
me. Thanks for the effort.

Reviewed-by: Xiao Ni <xni@redhat.com>