On Tue, Oct 13, 2015 at 10:07:12AM +0200, Jan Kara wrote: > On Mon 12-10-15 15:41:35, Ross Zwisler wrote: > > On Mon, Oct 12, 2015 at 10:14:43AM +1100, Dave Chinner wrote: > > > On Fri, Oct 09, 2015 at 04:02:08PM -0600, Ross Zwisler wrote: > > > > Add locking to ensure that DAX faults are isolated from ext2 operations > > > > that modify the data blocks allocation for an inode. This is intended to > > > > be analogous to the work being done in XFS by Dave Chinner: > > > > > > > > http://www.spinics.net/lists/linux-fsdevel/msg90260.html > > > > > > > > Compared with XFS the ext2 case is greatly simplified by the fact that ext2 > > > > already allocates and zeros new blocks before they are returned as part of > > > > ext2_get_block(), so DAX doesn't need to worry about getting unmapped or > > > > unwritten buffer heads. > > > > > > > > This means that the only work we need to do in ext2 is to isolate the DAX > > > > faults from inode block allocation changes. I believe this just means that > > > > we need to isolate the DAX faults from truncate operations. > > > > > > Why limit this just to DAX page faults? > > > > Yep, I see that XFS uses the same locking to protect both DAX and non-DAX > > faults. I'll add this protection to non-DAX ext2 faults as well. > > Actually, since ext2 driver doesn't support punch hole, there is no need > for additional locking in non-DAX paths. So we can save some space in inode > and locking for that common case. So I'd prefer if we didn't add > unnecessary locking in those paths and just document that for non-DAX > faults using page lock and i_size check is enough. After all the main > usecase of ext2 driver these days is for people with tiny devices... Based on this comment I'm assuming you'd like the definition of dax_sem in struct ext2_inode_info to be conditional like ext2_inode_info->xattr_sem, correct? -- 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
