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Subject[PATCH] erofs: fix erofs_get_meta_page locking by a cleanup
Date
After doing more drop_caches stress test on
our products, I found the mistake introduced by
a very recent cleanup [1].

The current rule is that "erofs_get_meta_page"
should be returned with page locked (although
it's mostly unnecessary for read-only fs after
pages are PG_Uptodate), but a fix should be
done for this.

[1] https://lore.kernel.org/r/20190904020912.63925-26-gaoxiang25@huawei.com
Fixes: 618f40ea026b ("erofs: use read_cache_page_gfp for erofs_get_meta_page")
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
---
fs/erofs/data.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/erofs/data.c b/fs/erofs/data.c
index 8a9fcbd0e8ac..e0207dba31cb 100644
--- a/fs/erofs/data.c
+++ b/fs/erofs/data.c
@@ -34,11 +34,17 @@ static void erofs_readendio(struct bio *bio)

struct page *erofs_get_meta_page(struct super_block *sb, erofs_blk_t blkaddr)
{
- struct inode *const bd_inode = sb->s_bdev->bd_inode;
- struct address_space *const mapping = bd_inode->i_mapping;
+ struct address_space *const mapping = sb->s_bdev->bd_inode->i_mapping;
+ struct page *page;

- return read_cache_page_gfp(mapping, blkaddr,
+ page = read_cache_page_gfp(mapping, blkaddr,
mapping_gfp_constraint(mapping, ~__GFP_FS));
+ if (IS_ERR(page))
+ return PTR_ERR(page);
+
+ /* should already be PageUptodate */
+ lock_page(page);
+ return page;
}

static int erofs_map_blocks_flatmode(struct inode *inode,
--
2.17.1
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