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| author | Jan Kara <jack@suse.com> | 2015-12-07 22:28:03 +0300 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2015-12-07 22:28:03 +0300 |
| commit | ea3d7209ca01da209cda6f0dea8be9cc4b7a933b (patch) | |
| tree | 809b37322befdf8dda2d12b991d1c832241bc8bc /fs/ext4/truncate.h | |
| parent | f41683a204ea61568f0fd0804d47c19561f2ee39 (diff) | |
| download | linux-ea3d7209ca01da209cda6f0dea8be9cc4b7a933b.tar.xz | |
ext4: fix races between page faults and hole punching
Currently, page faults and hole punching are completely unsynchronized.
This can result in page fault faulting in a page into a range that we
are punching after truncate_pagecache_range() has been called and thus
we can end up with a page mapped to disk blocks that will be shortly
freed. Filesystem corruption will shortly follow. Note that the same
race is avoided for truncate by checking page fault offset against
i_size but there isn't similar mechanism available for punching holes.
Fix the problem by creating new rw semaphore i_mmap_sem in inode and
grab it for writing over truncate, hole punching, and other functions
removing blocks from extent tree and for read over page faults. We
cannot easily use i_data_sem for this since that ranks below transaction
start and we need something ranking above it so that it can be held over
the whole truncate / hole punching operation. Also remove various
workarounds we had in the code to reduce race window when page fault
could have created pages with stale mapping information.
Signed-off-by: Jan Kara <jack@suse.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext4/truncate.h')
| -rw-r--r-- | fs/ext4/truncate.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/ext4/truncate.h b/fs/ext4/truncate.h index 011ba6670d99..c70d06a383e2 100644 --- a/fs/ext4/truncate.h +++ b/fs/ext4/truncate.h @@ -10,8 +10,10 @@ */ static inline void ext4_truncate_failed_write(struct inode *inode) { + down_write(&EXT4_I(inode)->i_mmap_sem); truncate_inode_pages(inode->i_mapping, inode->i_size); ext4_truncate(inode); + up_write(&EXT4_I(inode)->i_mmap_sem); } /* |