Re: 5.3-rc1 regression with XFS log recovery

["hch@lst.de" <hch@lst.de>]

On Sun, Aug 18, 2019 at 09:41:40AM +0200, hch@lst.de wrote:
> On Sun, Aug 18, 2019 at 09:11:28AM +0200, hch@lst.de wrote:
> > > The kernel log shows the following when the mount fails:
> > 
> > Is it always that same message?  I'll see if I can reproduce it,
> > but I won't have that much memory to spare to create fake pmem,
> > hope this also works with a single device and/or less memory..
> 
> I've reproduced a similar ASSERT with a small pmem device, so I hope
> I can debug the issue locally now.

So I can also reproduce the same issue with the ramdisk driver, but not
with any other 4k sector size device (nvmet, scsi target, scsi_debug,
loop).  Which made me wonder if there is some issue about the memory
passed in, and indeed just switching to plain vmalloc vs the XFS
kmem_alloc_large wrapper that either uses kmalloc or vmalloc fixes
the issue for me.  I don't really understand why yet, maybe I need to
dig out alignment testing patches.

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 13d1d3e95b88..918ad3b884a7 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -125,7 +125,7 @@ xlog_alloc_buffer(
 	if (nbblks > 1 && log->l_sectBBsize > 1)
 		nbblks += log->l_sectBBsize;
 	nbblks = round_up(nbblks, log->l_sectBBsize);
-	return kmem_alloc_large(BBTOB(nbblks), KM_MAYFAIL);
+	return vmalloc(BBTOB(nbblks));
 }
 
 /*
@@ -416,7 +416,7 @@ xlog_find_verify_cycle(
 	*new_blk = -1;
 
 out:
-	kmem_free(buffer);
+	vfree(buffer);
 	return error;
 }
 
@@ -527,7 +527,7 @@ xlog_find_verify_log_record(
 		*last_blk = i;
 
 out:
-	kmem_free(buffer);
+	vfree(buffer);
 	return error;
 }
 
@@ -781,7 +781,7 @@ xlog_find_head(
 			goto out_free_buffer;
 	}
 
-	kmem_free(buffer);
+	vfree(buffer);
 	if (head_blk == log_bbnum)
 		*return_head_blk = 0;
 	else
@@ -795,7 +795,7 @@ xlog_find_head(
 	return 0;
 
 out_free_buffer:
-	kmem_free(buffer);
+	vfree(buffer);
 	if (error)
 		xfs_warn(log->l_mp, "failed to find log head");
 	return error;
@@ -1049,7 +1049,7 @@ xlog_verify_tail(
 		"Tail block (0x%llx) overwrite detected. Updated to 0x%llx",
 			 orig_tail, *tail_blk);
 out:
-	kmem_free(buffer);
+	vfree(buffer);
 	return error;
 }
 
@@ -1096,7 +1096,7 @@ xlog_verify_head(
 	error = xlog_rseek_logrec_hdr(log, *head_blk, *tail_blk,
 				      XLOG_MAX_ICLOGS, tmp_buffer,
 				      &tmp_rhead_blk, &tmp_rhead, &tmp_wrapped);
-	kmem_free(tmp_buffer);
+	vfree(tmp_buffer);
 	if (error < 0)
 		return error;
 
@@ -1429,7 +1429,7 @@ xlog_find_tail(
 		error = xlog_clear_stale_blocks(log, tail_lsn);
 
 done:
-	kmem_free(buffer);
+	vfree(buffer);
 
 	if (error)
 		xfs_warn(log->l_mp, "failed to locate log tail");
@@ -1477,7 +1477,7 @@ xlog_find_zeroed(
 	first_cycle = xlog_get_cycle(offset);
 	if (first_cycle == 0) {		/* completely zeroed log */
 		*blk_no = 0;
-		kmem_free(buffer);
+		vfree(buffer);
 		return 1;
 	}
 
@@ -1488,7 +1488,7 @@ xlog_find_zeroed(
 
 	last_cycle = xlog_get_cycle(offset);
 	if (last_cycle != 0) {		/* log completely written to */
-		kmem_free(buffer);
+		vfree(buffer);
 		return 0;
 	}
 
@@ -1535,7 +1535,7 @@ xlog_find_zeroed(
 
 	*blk_no = last_blk;
 out_free_buffer:
-	kmem_free(buffer);
+	vfree(buffer);
 	if (error)
 		return error;
 	return 1;
@@ -1647,7 +1647,7 @@ xlog_write_log_records(
 	}
 
 out_free_buffer:
-	kmem_free(buffer);
+	vfree(buffer);
 	return error;
 }
 
@@ -5291,7 +5291,7 @@ xlog_do_recovery_pass(
 			hblks = h_size / XLOG_HEADER_CYCLE_SIZE;
 			if (h_size % XLOG_HEADER_CYCLE_SIZE)
 				hblks++;
-			kmem_free(hbp);
+			vfree(hbp);
 			hbp = xlog_alloc_buffer(log, hblks);
 		} else {
 			hblks = 1;
@@ -5307,7 +5307,7 @@ xlog_do_recovery_pass(
 		return -ENOMEM;
 	dbp = xlog_alloc_buffer(log, BTOBB(h_size));
 	if (!dbp) {
-		kmem_free(hbp);
+		vfree(hbp);
 		return -ENOMEM;
 	}
 
@@ -5468,9 +5468,9 @@ xlog_do_recovery_pass(
 	}
 
  bread_err2:
-	kmem_free(dbp);
+	vfree(dbp);
  bread_err1:
-	kmem_free(hbp);
+	vfree(hbp);
 
 	/*
 	 * Submit buffers that have been added from the last record processed,