bcachefs: Improve locking in __bch2_set_nr_journal_buckets()

This refactors to not call bch2_journal_block() with c->sb_lock held.

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

diff --git a/fs/bcachefs/journal.c b/fs/bcachefs/journal.c
index 66bd0a72c77472416ba05570bc88c291dcac5714..00e806a6424721810c3e5b8a4b2a5d33e3f8873c 100644 (file)
--- a/fs/bcachefs/journal.c
+++ b/fs/bcachefs/journal.c
@@ -768,6 +768,7 @@ static int __bch2_set_nr_journal_buckets(struct bch_dev *ca, unsigned nr,
        if (c) {
                bch2_journal_flush_all_pins(&c->journal);
                bch2_journal_block(&c->journal);
+               mutex_lock(&c->sb_lock);
        }
 
        bu              = kcalloc(nr_want, sizeof(*bu), GFP_KERNEL);
@@ -848,6 +849,9 @@ static int __bch2_set_nr_journal_buckets(struct bch_dev *ca, unsigned nr,
        if (!new_fs)
                spin_unlock(&c->journal.lock);
 
+       if (ja->nr != old_nr && !new_fs)
+               bch2_write_super(c);
+
        if (c)
                bch2_journal_unblock(&c->journal);
 
@@ -867,6 +871,9 @@ static int __bch2_set_nr_journal_buckets(struct bch_dev *ca, unsigned nr,
                }
        }
 err:
+       if (c)
+               mutex_unlock(&c->sb_lock);
+
        if (ob && !new_fs)
                for (i = 0; i < nr_got; i++)
                        bch2_open_bucket_put(c, ob[i]);
@@ -892,7 +899,6 @@ int bch2_set_nr_journal_buckets(struct bch_fs *c, struct bch_dev *ca,
 {
        struct journal_device *ja = &ca->journal;
        struct closure cl;
-       unsigned current_nr;
        int ret = 0;
 
        /* don't handle reducing nr of buckets yet: */
@@ -901,44 +907,44 @@ int bch2_set_nr_journal_buckets(struct bch_fs *c, struct bch_dev *ca,
 
        closure_init_stack(&cl);
 
-       while (ja->nr != nr && (ret == 0 || ret == -BCH_ERR_bucket_alloc_blocked)) {
+       while (ja->nr != nr) {
                struct disk_reservation disk_res = { 0, 0 };
 
-               closure_sync(&cl);
-
-               mutex_lock(&c->sb_lock);
-               current_nr = ja->nr;
-
                /*
                 * note: journal buckets aren't really counted as _sectors_ used yet, so
                 * we don't need the disk reservation to avoid the BUG_ON() in buckets.c
                 * when space used goes up without a reservation - but we do need the
                 * reservation to ensure we'll actually be able to allocate:
+                *
+                * XXX: that's not right, disk reservations only ensure a
+                * filesystem-wide allocation will succeed, this is a device
+                * specific allocation - we can hang here:
                 */
 
                ret = bch2_disk_reservation_get(c, &disk_res,
                                                bucket_to_sector(ca, nr - ja->nr), 1, 0);
-               if (ret) {
-                       mutex_unlock(&c->sb_lock);
-                       return ret;
-               }
+               if (ret)
+                       break;
 
                ret = __bch2_set_nr_journal_buckets(ca, nr, false, &cl);
 
                bch2_disk_reservation_put(c, &disk_res);
 
-               if (ja->nr != current_nr)
-                       bch2_write_super(c);
-               mutex_unlock(&c->sb_lock);
+               closure_sync(&cl);
+
+               if (ret && ret != -BCH_ERR_bucket_alloc_blocked)
+                       break;
        }
 
+       if (ret)
+               bch_err(c, "%s: err %s", __func__, bch2_err_str(ret));
+
        return ret;
 }
 
 int bch2_dev_journal_alloc(struct bch_dev *ca)
 {
        unsigned nr;
-       int ret;
 
        if (dynamic_fault("bcachefs:add:journal_alloc"))
                return -ENOMEM;
@@ -955,15 +961,7 @@ int bch2_dev_journal_alloc(struct bch_dev *ca)
                     min(1 << 13,
                         (1 << 24) / ca->mi.bucket_size));
 
-       if (ca->fs)
-               mutex_lock(&ca->fs->sb_lock);
-
-       ret = __bch2_set_nr_journal_buckets(ca, nr, true, NULL);
-
-       if (ca->fs)
-               mutex_unlock(&ca->fs->sb_lock);
-
-       return ret;
+       return __bch2_set_nr_journal_buckets(ca, nr, true, NULL);
 }
 
 /* startup/shutdown: */