tree 413d9b1af6fd9b916c0bdb9f7380d5657c093efb
parent ce140cdd9c171dc75cfdcfee2b8708c508f5daf6
author Maxim Patlasov <MPatlasov@parallels.com> 1392933485 -0500
committer Theodore Ts'o <tytso@mit.edu> 1392933485 -0500

ext4: avoid exposure of stale data in ext4_punch_hole()

While handling punch-hole fallocate, it's useless to truncate page cache
before removing the range from extent tree (or block map in indirect case)
because page cache can be re-populated (by read-ahead or read(2) or mmap-ed
read) immediately after truncating page cache, but before updating extent
tree (or block map). In that case the user will see stale data even after
fallocate is completed.

Until the problem of data corruption resulting from pages backed by
already freed blocks is fully resolved, the simple thing we can do now
is to add another truncation of pagecache after punch hole is done.

Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>