linux-ext4 - Re: [PATCH 06/10] hugetlbfs: Convert remove_inode_hugepages() to use filemap_get

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Date:   Fri, 10 Jun 2022 22:17:36 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Sumanth Korikkar <sumanthk@...ux.ibm.com>
Cc:     linux-ext4@...r.kernel.org, gerald.schaefer@...ux.ibm.com,
        gor@...ux.ibm.com, agordeev@...ux.ibm.com,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-nilfs@...r.kernel.org
Subject: Re: [PATCH 06/10] hugetlbfs: Convert remove_inode_hugepages() to use
 filemap_get_folios()

On Fri, Jun 10, 2022 at 05:52:05PM +0200, Sumanth Korikkar wrote:
> To reproduce:
> * clone libhugetlbfs:
> * Execute, PATH=$PATH:"obj64/" LD_LIBRARY_PATH=../obj64/ alloc-instantiate-race shared

... it's a lot harder to set up hugetlb than that ...

anyway, i figured it out without being able to run the reproducer.

Can you try this?

diff --git a/mm/filemap.c b/mm/filemap.c
index a30587f2e598..8ef861297ffb 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2160,7 +2160,11 @@ unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,
 		if (xa_is_value(folio))
 			continue;
 		if (!folio_batch_add(fbatch, folio)) {
-			*start = folio->index + folio_nr_pages(folio);
+			unsigned long nr = folio_nr_pages(folio);
+
+			if (folio_test_hugetlb(folio))
+				nr = 1;
+			*start = folio->index + nr;
 			goto out;
 		}
 	}