Re: [PATCH v2 1/8] migrate: fix skipping metadata buffer heads on migration

[Matthew Wilcox <willy@infradead.org>]

On Wed, Apr 09, 2025 at 06:49:38PM -0700, Luis Chamberlain wrote:
> +++ b/mm/migrate.c
> @@ -841,6 +841,9 @@ static int __buffer_migrate_folio(struct address_space *mapping,
>  	if (folio_ref_count(src) != expected_count)
>  		return -EAGAIN;
>  
> +	if (buffer_meta(head))
> +		return -EAGAIN;

This isn't enough on filesystems with bs<PS.  You're only testing the
meta bit on the first buffer_head on the folio and not on the rest of
them.  If this is the right approach to take, then we want:

+++ b/mm/migrate.c
@@ -799,6 +799,8 @@ static bool buffer_migrate_lock_buffers(struct buffer_head *head,
        struct buffer_head *failed_bh;

        do {
+               if (buffer_meta(bh))
+                       goto unlock;
                if (!trylock_buffer(bh)) {
                        if (mode == MIGRATE_ASYNC)
                                goto unlock;