linux-kernel - [PATCH] erofs: apply proper VMA alignment for memory mapped files on THP

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Date: Wed,  6 Mar 2024 13:31:38 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: linux-erofs@...ts.ozlabs.org
Cc: LKML <linux-kernel@...r.kernel.org>,
	Gao Xiang <hsiangkao@...ux.alibaba.com>
Subject: [PATCH] erofs: apply proper VMA alignment for memory mapped files on THP

There are mainly two reasons that thp_get_unmapped_area() should be
used for EROFS as other filesystems:

 - It's needed to enable PMD mappings as a FSDAX filesystem, see
   commit 74d2fad1334d ("thp, dax: add thp_get_unmapped_area for pmd
   mappings");

 - It's useful together with CONFIG_READ_ONLY_THP_FOR_FS which enables
   THPs for read-only mmapped files (e.g. shared libraries) even without
   FSDAX.  See commit 1854bc6e2420 ("mm/readahead: Align file mappings
   for non-DAX").

Fixes: 06252e9ce05b ("erofs: dax support for non-tailpacking regular file")
Signed-off-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
---
 fs/erofs/data.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/erofs/data.c b/fs/erofs/data.c
index c98aeda8abb2..3d9721b3faa8 100644
--- a/fs/erofs/data.c
+++ b/fs/erofs/data.c
@@ -447,5 +447,6 @@ const struct file_operations erofs_file_fops = {
 	.llseek		= generic_file_llseek,
 	.read_iter	= erofs_file_read_iter,
 	.mmap		= erofs_file_mmap,
+	.get_unmapped_area = thp_get_unmapped_area,
 	.splice_read	= filemap_splice_read,
 };
-- 
2.39.3