On 11.05.2018 09:30, Omar Sandoval wrote: > From: Omar Sandoval <osandov@xxxxxx> > > Hi, everyone, > > Btrfs currently abuses current->journal_info in btrfs_direct_IO() in > order to pass around some state to get_block() and submit_io(). This > hack is ugly and unnecessary because the data we pass around is only > used in one call frame. Robbie Ko also pointed out [1] that it could > potentially cause a crash if we happen to end up in start_transaction() > (e.g., from memory reclaim calling into btrfs_evict_inode(), which can > start a transaction). I'm not convinced that Robbie's case can happen in > practice since we are using GFP_NOFS for allocations during direct I/O, > but either way it's fragile and nasty. When I worked initially on btrfs-over-swap I managed to hit a case where ext4 stacked on top of btrfs would crash since btrfs will overwrite journal_info which was set by ext4. So this change is indeed welcome :) > > This series stops using current->journal_info and instead adds some > extra arguments to the generic direct I/O code so that we can pass > things around like sane people. > > Based on Linus' master. > > Thanks! > > 1: https://patchwork.kernel.org/patch/10389077/ > > Omar Sandoval (3): > fs: add initial bh_result->b_private value to __blockdev_direct_IO() > fs: add private argument to dio_submit_t > Btrfs: stop abusing current->journal_info in btrfs_direct_IO() > > fs/btrfs/inode.c | 39 ++++++++++----------------------------- > fs/direct-io.c | 12 +++++++----- > fs/ext4/inode.c | 6 +++--- > fs/gfs2/aops.c | 2 +- > fs/ocfs2/aops.c | 5 ++--- > include/linux/fs.h | 10 +++++----- > 6 files changed, 28 insertions(+), 46 deletions(-) >
