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? -- 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
