On Fri, Jan 20, 2012 at 09:34:43PM +0100, Jan Kara wrote: > Replace racy xfs_wait_for_freeze() check in xfs_file_aio_write() with > a reliable sb_start_write() - sb_end_write() locking. Due to lock ranking > dictated by the page fault code we have to call sb_start_write() after we > acquire ilock. It appears to me that you have indeed confused the ilock with the iolock. > Similarly we have to protect xfs_setattr_size() because it can modify last > page of truncated file. Because ilock is dropped in xfs_setattr_size() we > have to drop and retake write access as well to avoid deadlocks. > > CC: Ben Myers <bpm@xxxxxxx> > CC: Alex Elder <elder@xxxxxxxxxx> > Signed-off-by: Jan Kara <jack@xxxxxxx> > --- > fs/xfs/xfs_file.c | 6 ++++-- > fs/xfs/xfs_iops.c | 6 ++++++ > 2 files changed, 10 insertions(+), 2 deletions(-) > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > index 753ed9b..9efd153 100644 > --- a/fs/xfs/xfs_file.c > +++ b/fs/xfs/xfs_file.c > @@ -862,9 +862,11 @@ xfs_file_dio_aio_write( > *iolock = XFS_IOLOCK_SHARED; > } > > + sb_start_write(inode->i_sb, SB_FREEZE_WRITE); > trace_xfs_file_direct_write(ip, count, iocb->ki_pos, 0); > ret = generic_file_direct_write(iocb, iovp, > &nr_segs, pos, &iocb->ki_pos, count, ocount); > + sb_end_write(inode->i_sb, SB_FREEZE_WRITE); That's inside the iolock, not the ilock. Either way, it is incorrect. This accounting should be outside the iolock - because xfs_trans_alloc() can be called with the iolock held. Therefore the freeze/lock order needs to be sb_start_write(SB_FREEZE_WRITE) XFS(ip)->i_iolock XFS(ip)->i_ilock sb_end_write(SB_FREEZE_WRITE) Which matches the current freeze/lock order. > @@ -945,8 +949,6 @@ xfs_file_aio_write( > if (ocount == 0) > return 0; > > - xfs_wait_for_freeze(ip->i_mount, SB_FREEZE_WRITE); > - that's where sb_start_write() needs to be, and the sb-end_write() call needs to below the generic_write_sync() calls that will trigger IO on O_SYNC writes. Otherwise it is not covering all the IO path correctly. > if (XFS_FORCED_SHUTDOWN(ip->i_mount)) > return -EIO; > > diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c > index 3579bc8..798b9c6 100644 > --- a/fs/xfs/xfs_iops.c > +++ b/fs/xfs/xfs_iops.c > @@ -793,6 +793,7 @@ xfs_setattr_size( > return xfs_setattr_nonsize(ip, iattr, 0); > } > > + sb_start_write(inode->i_sb, SB_FREEZE_WRITE); > /* > * Make sure that the dquots are attached to the inode. > */ > @@ -849,10 +850,14 @@ xfs_setattr_size( > xfs_get_blocks); > if (error) > goto out_unlock; > + /* Drop the write access to avoid lock inversion with ilock */ > + sb_end_write(inode->i_sb, SB_FREEZE_WRITE); > > xfs_ilock(ip, XFS_ILOCK_EXCL); > lock_flags |= XFS_ILOCK_EXCL; > > + sb_start_write(inode->i_sb, SB_FREEZE_WRITE); > + This is caused by the previous problems I pointed out. You should not need to drop the freeze reference here at all. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
