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1a0bd289a5
Case #1:
SQLite App GC Thread Kworker Shrinker
- f2fs_ioc_start_atomic_write
- f2fs_ioc_commit_atomic_write
- f2fs_commit_atomic_write
- filemap_write_and_wait_range
: write atomic_file's data to cow_inode
echo 3 > drop_caches
to drop atomic_file's
cache.
- f2fs_gc
- gc_data_segment
- move_data_page
- set_page_dirty
- writepages
- f2fs_do_write_data_page
: overwrite atomic_file's data
to cow_inode
- f2fs_down_write(&fi->i_gc_rwsem[WRITE])
- __f2fs_commit_atomic_write
- f2fs_up_write(&fi->i_gc_rwsem[WRITE])
Case #2:
SQLite App GC Thread Kworker
- f2fs_ioc_start_atomic_write
- __writeback_single_inode
- do_writepages
- f2fs_write_cache_pages
- f2fs_write_single_data_page
- f2fs_do_write_data_page
: write atomic_file's data to cow_inode
- f2fs_gc
- gc_data_segment
- move_data_page
- set_page_dirty
- writepages
- f2fs_do_write_data_page
: overwrite atomic_file's data to cow_inode
- f2fs_ioc_commit_atomic_write
In above cases racing in between atomic_write and GC, previous
data in atomic_file may be overwrited to cow_file, result in
data corruption.
This patch introduces PAGE_PRIVATE_ATOMIC_WRITE bit flag in page.private,
and use it to indicate that there is last dirty data in atomic file,
and the data should be writebacked into cow_file, if the flag is not
tagged in page, we should never write data across files.
Fixes: 3db1de0e58 ("f2fs: change the current atomic write way")
Cc: Daeho Jeong <daehojeong@google.com>
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.