From: Dmitry Monakhov Date: Fri, 5 Oct 2012 15:31:55 +0000 (-0400) Subject: ext4: fix ext4_flush_completed_IO wait semantics X-Git-Tag: v3.7-rc1~91^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c278531d39f3158bfee93dc67da0b77e09776de2;p=pandora-kernel.git ext4: fix ext4_flush_completed_IO wait semantics BUG #1) All places where we call ext4_flush_completed_IO are broken because buffered io and DIO/AIO goes through three stages 1) submitted io, 2) completed io (in i_completed_io_list) conversion pended 3) finished io (conversion done) And by calling ext4_flush_completed_IO we will flush only requests which were in (2) stage, which is wrong because: 1) punch_hole and truncate _must_ wait for all outstanding unwritten io regardless to it's state. 2) fsync and nolock_dio_read should also wait because there is a time window between end_page_writeback() and ext4_add_complete_io() As result integrity fsync is broken in case of buffered write to fallocated region: fsync blkdev_completion ->filemap_write_and_wait_range ->ext4_end_bio ->end_page_writeback <-- filemap_write_and_wait_range return ->ext4_flush_completed_IO sees empty i_completed_io_list but pended conversion still exist ->ext4_add_complete_io BUG #2) Race window becomes wider due to the 'ext4: completed_io locking cleanup V4' patch series This patch make following changes: 1) ext4_flush_completed_io() now first try to flush completed io and when wait for any outstanding unwritten io via ext4_unwritten_wait() 2) Rename function to more appropriate name. 3) Assert that all callers of ext4_flush_unwritten_io should hold i_mutex to prevent endless wait Signed-off-by: Dmitry Monakhov Signed-off-by: "Theodore Ts'o" Reviewed-by: Jan Kara --- Reading git-diff-tree failed