Hi Matthew, On Fri, Jul 23, 2021 at 08:40:51PM +0100, Matthew Wilcox wrote: > On Sat, Jul 24, 2021 at 01:41:31AM +0800, Gao Xiang wrote: > > Add support for reading inline data content into the page cache from > > nonzero page-aligned file offsets. This enables the EROFS tailpacking > > mode where the last few bytes of the file are stored right after the > > inode. > > > > The buffered write path remains untouched since EROFS cannot be used > > for testing. It'd be better to be implemented if upcoming real users > > care and provide a real pattern rather than leave untested dead code > > around. > > My one complaint with this version is the subject line. It's a bit vague. > I went with: > > iomap: Support file tail packing > > I also wrote a changelog entry that reads: > The existing inline data support only works for cases where the entire > file is stored as inline data. For larger files, EROFS stores the > initial blocks separately and then can pack a small tail adjacent to > the inode. Generalise inline data to allow for tail packing. Tails > may not cross a page boundary in memory. > Yeah, we could complete the commit message like this. Actually EROFS inode base is only 32-byte or 64-byte (so the maximum could not be exactly small), compared to using another tail block or storing other (maybe) irrelevant inodes. According to cache locality principle, a strategy can be selected by mkfs to load tail block with the inode base itself to the page cache by the tail-packing inline and so reduce I/O and fragmentation. > ... but I'm not sure that's necessarily better than what you've written > here. > > > Cc: Christoph Hellwig <hch@xxxxxx> > > Cc: Darrick J. Wong <djwong@xxxxxxxxxx> > > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > > Cc: Andreas Gruenbacher <andreas.gruenbacher@xxxxxxxxx> > > Tested-by: Huang Jianan <huangjianan@xxxxxxxx> # erofs > > Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx> > > Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Many thanks for the review! Thanks, Gao Xiang
