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 <hsiang...@linux.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

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