On Tue, Sep 10, 2019 at 02:28:35PM +0200, Carlos Maiolino wrote: > Hey, thanks for the info. > > Although.. > > On Thu, Aug 29, 2019 at 09:15:55AM +0200, Christoph Hellwig wrote: > > On Tue, Aug 20, 2019 at 03:01:18PM +0200, Carlos Maiolino wrote: > > > On Wed, Aug 14, 2019 at 01:18:37PM +0200, Christoph Hellwig wrote: > > > > The whole FIEMAP_KERNEL_FIBMAP thing looks very counter productive. > > > > bmap() should be able to make the right decision based on the passed > > > > in flags, no need to have a fake FIEMAP flag for that. > > > > > > Using the FIEMAP_KERNEL_FIBMAP flag, is a way to tell filesystems from where the > > > request came from, so filesystems can handle it differently. For example, we > > > can't allow in XFS a FIBMAP request on a COW/RTIME inode, and we use the FIBMAP > > > flag in such situations. > > > > But the whole point is that the file system should not have to know > > this. It is not the file systems business in any way to now where the > > call came from. The file system just needs to provide enough information > > so that the caller can make informed decisions. > > > > And in this case that means if any of FIEMAP_EXTENT_DELALLOC, > > FIEMAP_EXTENT_ENCODED, FIEMAP_EXTENT_DATA_ENCRYPTED, > > FIEMAP_EXTENT_NOT_ALIGNED, FIEMAP_EXTENT_DATA_INLINE, > > FIEMAP_EXTENT_DATA_TAIL, FIEMAP_EXTENT_UNWRITTEN or > > FIEMAP_EXTENT_SHARED is present the caller should fail the > > bmap request. > > This seems doable, yes, but... Doing that essentially will make some > filesystems, like BTRFS, to suddenly start to support fibmap, this was another > reason why we opted in the first place to let filesystems know whom the caller > was. > > We could maybe add a new FIEMAP_EXTENT_* flag in the future to, let's say, > specify a specific block may be split between more than one device, but, well. > It's an idea, but it won't change the fact BTRFS for example will suddenly start > to support FIBMAP. ...or burn another superblock sb_flag on "this fs supports FIBMAP"; have the in-kernel bmap() function bail out if it isn't set; and only set it for the filesystems that used to supply ->bmap? --D > -- > Carlos
