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erofs: get correct count for unmapped range in fscache mode

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[ Upstream commit e6d9f9ba11 ]

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 1ae9470c3e ("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: c665b394b9 ("erofs: implement fscache-based data readahead")
Fixes: 1ae9470c3e ("erofs: clean up .read_folio() and .readahead() in fscache mode")
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20221104054028.52208-3-jefflexu@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Jingbo Xu 2022-11-04 13:40:28 +08:00 committed by Greg Kroah-Hartman
parent f1f28d9b7e
commit 73ed0cd917
1 changed files with 4 additions and 3 deletions
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7
fs/erofs/fscache.c
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@ -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,