On Tue, Jul 27, 2021 at 02:35:46PM +0100, Matthew Wilcox wrote: > On Tue, Jul 27, 2021 at 10:20:42AM +0200, David Sterba wrote: > > On Mon, Jul 26, 2021 at 02:17:02PM +0200, Christoph Hellwig wrote: > > > > Subject: iomap: Support tail packing > > > > > > I can't say I like this "tail packing" language here when we have the > > > perfectly fine inline wording. Same for various comments in the actual > > > code. > > > > Yes please, don't call it tail-packing when it's an inline extent, we'll > > use that for btrfs eventually and conflating the two terms has been > > cofusing users. Except reiserfs, no linux filesystem does tail-packing. > > Hmm ... I see what reiserfs does as packing tails of multiple files into > one block. What gfs2 (and ext4) do is inline data. Erofs packs the > tail of a single file into the same block as the inode. If I understand > what btrfs does correctly, it stores data in the btree. But (like > gfs2/ext4), it's only for the entire-file-is-small case, not for > its-just-ten-bytes-into-the-last-block case. > > So what would you call what erofs is doing if not tail-packing? That indeed sounds like tail-packing and I was not aware of that, the docs I found were not clear what exactly was going on with the data stored inline. > Wikipedia calls it https://en.wikipedia.org/wiki/Block_suballocation > which doesn't quite fit. We need a phrase which means "this isn't > just for small files but for small tails of large files". So that's more generic than what we now have as inline files, so in the interface everybody sets 0 as start of the range while erofs can also set start of the last partial block.
