On Fri, Oct 09, 2015 at 03:18:11PM -0700, Dan Williams wrote: > On Fri, Oct 9, 2015 at 3:02 PM, Ross Zwisler > <ross.zwisler@xxxxxxxxxxxxxxx> 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. > > > > The newly introduced dax_sem is intended to replicate the protection > > offered by i_mmaplock in XFS. In addition to truncate the i_mmaplock also > > protects XFS operations like hole punching, fallocate down, extent > > manipulation IOCTLS like xfs_ioc_space() and extent swapping. Truncate is > > the only one of these operations supported by ext2. > > > > Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> > [..] > > ...not a review of the ext2 changes. > > > diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c > > index c60a248..2b974fc 100644 > > --- a/fs/ext2/inode.c > > +++ b/fs/ext2/inode.c > > @@ -1085,6 +1085,7 @@ static void ext2_free_branches(struct inode *inode, __le32 *p, __le32 *q, int de > > ext2_free_data(inode, p, q); > > } > > > > +/* dax_sem must be held when calling this function */ > > static void __ext2_truncate_blocks(struct inode *inode, loff_t offset) > > { > > How about a "WARN_ON(!rwsem_is_locked(&ei->dax_sem));" to backstop > this assumption? Yep, sounds like a good idea. Thanks. -- 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
