From: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
[ Upstream commit e6d9f9ba111b56154f1b1120252aff269cebd49c ]
For unmapped range, the returned map.m_llen is zero, and thus the
calculated count is unexpected zero.
Prior to the refactoring introduced by commit 1ae9470c3e14 ("erofs:
clean up .read_folio() and .readahead() in fscache mode"), only the
readahead routine suffers from this. With the refactoring of making
.read_folio() and .readahead() calling one common routine, both
read_folio and readahead have this issue now.
Fix this by calculating count separately in unmapped condition.
Fixes: c665b394b9e8 ("erofs: implement fscache-based data readahead")
Fixes: 1ae9470c3e14 ("erofs: clean up .read_folio() and .readahead() in fscache mode")
Signed-off-by: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
Reviewed-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>
Reviewed-by: Chao Yu <chao@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20221104054028.52208-3-jefflexu@xxxxxxxxxxxxxxxxx
Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/erofs/fscache.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index 508b1a4df15e..8585e324298c 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -288,15 +288,16 @@ static int erofs_fscache_data_read(struct address_space *mapping,
return PAGE_SIZE;
}
- count = min_t(size_t, map.m_llen - (pos - map.m_la), len);
- DBG_BUGON(!count || count % PAGE_SIZE);
-
if (!(map.m_flags & EROFS_MAP_MAPPED)) {
+ count = len;
iov_iter_xarray(&iter, READ, &mapping->i_pages, pos, count);
iov_iter_zero(count, &iter);
return count;
}
+ count = min_t(size_t, map.m_llen - (pos - map.m_la), len);
+ DBG_BUGON(!count || count % PAGE_SIZE);
+
mdev = (struct erofs_map_dev) {
.m_deviceid = map.m_deviceid,
.m_pa = map.m_pa,
--
2.35.1
