[PATCH 2/3] bcachefs: Fix *__bch2_trans_subbuf_alloc() error path

[Kent Overstreet]

Don't change buf->size on error - this would usually be a transaction
restart, but it could also be -ENOMEM - when we've exceeded the bump
allocator max).

Fixes: 247abee6ae6d ("bcachefs: btree_trans_subbuf")
Signed-off-by: Kent Overstreet <kent.overstr...@linux.dev>
---
 fs/bcachefs/btree_update.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/fs/bcachefs/btree_update.c b/fs/bcachefs/btree_update.c
index f7949dbe8f70..668d4feb2879 100644
--- a/fs/bcachefs/btree_update.c
+++ b/fs/bcachefs/btree_update.c
@@ -550,19 +550,26 @@ void *__bch2_trans_subbuf_alloc(struct btree_trans *trans,
 {
        unsigned new_top = buf->u64s + u64s;
        unsigned old_size = buf->size;
+       unsigned new_size = buf->size;
 
-       if (new_top > buf->size)
-               buf->size = roundup_pow_of_two(new_top);
+       BUG_ON(roundup_pow_of_two(new_top) > U16_MAX);
 
-       void *n = bch2_trans_kmalloc_nomemzero_ip(trans, buf->size * 
sizeof(u64), ip);
+       if (new_top > new_size)
+               new_size = roundup_pow_of_two(new_top);
+
+       void *n = bch2_trans_kmalloc_nomemzero_ip(trans, new_size * 
sizeof(u64), ip);
        if (IS_ERR(n))
                return n;
 
+       unsigned offset = (u64 *) n - (u64 *) trans->mem;
+       BUG_ON(offset > U16_MAX);
+
        if (buf->u64s)
                memcpy(n,
                       btree_trans_subbuf_base(trans, buf),
                       old_size * sizeof(u64));
        buf->base = (u64 *) n - (u64 *) trans->mem;
+       buf->size = new_size;
 
        void *p = btree_trans_subbuf_top(trans, buf);
        buf->u64s = new_top;
-- 
2.50.0