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different competitors
Since we use different page cache (normally inode's page cache for R/W
and meta inode's page cache for GC) to cache the same physical block
which is belong to an encrypted inode. Writeback of these two page
cache should be exclusive, but now we didn't handle writeback state
well, so there may be potential racing problem:
a)
kworker: f2fs_gc:
- f2fs_write_data_pages
- f2fs_write_data_page
- do_write_data_page
- write_data_page
- f2fs_submit_page_mbio
(page#1 in inode's page cache was queued
in f2fs bio cache, and be ready to write
to new blkaddr)
- gc_data_segment
- move_encrypted_block
- pagecache_get_page
(page#2 in meta inode's page cache
was cached with the invalid datas
of physical block located in new
blkaddr)
- f2fs_submit_page_mbio
(page#1 was submitted, later, page#2
with invalid data will be submitted)
b)
f2fs_gc:
- gc_data_segment
- move_encrypted_block
- f2fs_submit_page_mbio
(page#1 in meta inode's page cache was
queued in f2fs bio cache, and be ready
to write to new blkaddr)
user thread:
- f2fs_write_begin
- f2fs_submit_page_bio
(we submit the request to block layer
to update page#2 in inode's page cache
with physical block located in new
blkaddr, so here we may read gabbage
data from new blkaddr since GC hasn't
writebacked the page#1 yet)
This patch fixes above potential racing problem for encrypted inode.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
08b39fbd59