bcachefs: Simplify journal read path

This just cleans up and simplifies the code that decides where to resume
writing in the journal - when the code was originally written we weren't
saving the precise location of every journal write found.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/journal_io.c b/fs/bcachefs/journal_io.c
index a5c9524aa6e76a846d4793bd019498a48c5e9478..854a0685db09dfb47d354d02eaeb36a08d1484b6 100644 (file)
--- a/fs/bcachefs/journal_io.c
+++ b/fs/bcachefs/journal_io.c
@@ -986,7 +986,6 @@ static void bch2_journal_read_device(struct closure *cl)
        struct journal_replay *r, **_r;
        struct genradix_iter iter;
        struct journal_read_buf buf = { NULL, 0 };
-       u64 min_seq = U64_MAX;
        unsigned i;
        int ret = 0;
 
@@ -1005,45 +1004,27 @@ static void bch2_journal_read_device(struct closure *cl)
                        goto err;
        }
 
-       /* Find the journal bucket with the highest sequence number: */
-       for (i = 0; i < ja->nr; i++) {
-               if (ja->bucket_seq[i] > ja->bucket_seq[ja->cur_idx])
-                       ja->cur_idx = i;
-
-               min_seq = min(ja->bucket_seq[i], min_seq);
-       }
-
-       /*
-        * If there's duplicate journal entries in multiple buckets (which
-        * definitely isn't supposed to happen, but...) - make sure to start
-        * cur_idx at the last of those buckets, so we don't deadlock trying to
-        * allocate
-        */
-       while (ja->bucket_seq[ja->cur_idx] > min_seq &&
-              ja->bucket_seq[ja->cur_idx] ==
-              ja->bucket_seq[(ja->cur_idx + 1) % ja->nr])
-               ja->cur_idx = (ja->cur_idx + 1) % ja->nr;
-
        ja->sectors_free = ca->mi.bucket_size;
 
        mutex_lock(&jlist->lock);
-       genradix_for_each(&c->journal_entries, iter, _r) {
+       genradix_for_each_reverse(&c->journal_entries, iter, _r) {
                r = *_r;
 
                if (!r)
                        continue;
 
                for (i = 0; i < r->nr_ptrs; i++) {
-                       if (r->ptrs[i].dev == ca->dev_idx &&
-                           sector_to_bucket(ca, r->ptrs[i].sector) == ja->buckets[ja->cur_idx]) {
+                       if (r->ptrs[i].dev == ca->dev_idx) {
                                unsigned wrote = bucket_remainder(ca, r->ptrs[i].sector) +
                                        vstruct_sectors(&r->j, c->block_bits);
 
-                               ja->sectors_free = min(ja->sectors_free,
-                                                      ca->mi.bucket_size - wrote);
+                               ja->cur_idx = r->ptrs[i].bucket;
+                               ja->sectors_free = ca->mi.bucket_size - wrote;
+                               goto found;
                        }
                }
        }
+found:
        mutex_unlock(&jlist->lock);
 
        if (ja->bucket_seq[ja->cur_idx] &&