From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> This series adds a readahead address_space operation to eventually replace the readpages operation. The key difference is that pages are added to the page cache as they are allocated (and then looked up by the filesystem) instead of passing them on a list to the readpages operation and having the filesystem add them to the page cache. It's a net reduction in code for each implementation, more efficient than walking a list, and solves the direct-write vs buffered-read problem reported by yu kuai at https://lore.kernel.org/linux-fsdevel/20200116063601.39201-1-yukuai3@xxxxxxxxxx/ The only unconverted filesystems are those which use fscache. Their conversion is pending Dave Howells' rewrite which will make the conversion substantially easier. v6: - Name the private members of readahead_control with a leading underscore (suggested by Christoph Hellwig) - Fix whitespace in rst file - Remove misleading comment in btrfs patch - Add readahead_next() API and use it in iomap - Add iomap_readahead kerneldoc. - Fix the mpage_readahead kerneldoc - Make various readahead functions return void - Keep readahead_index() and readahead_offset() pointing to the start of this batch through the body. No current user requires this, but it's less surprising. - Add kerneldoc for page_cache_readahead_limit - Make page_idx an unsigned long, and rename it to just 'i' - Get rid of page_offset local variable - Add patch to call memalloc_nofs_save() before allocating pages (suggested by Michal Hocko) - Resplit a lot of patches for more logical progression and easier review (suggested by John Hubbard) - Added sign-offs where received, and I deemed still relevant v5 switched to passing a readahead_control struct (mirroring the writepages_control struct passed to writepages). This has a number of advantages: - It fixes a number of bugs in various implementations, eg forgetting to increment 'start', an off-by-one error in 'nr_pages' or treating 'start' as a byte offset instead of a page offset. - It allows us to change the arguments without changing all the implementations of ->readahead which just call mpage_readahead() or iomap_readahead() - Figuring out which pages haven't been attempted by the implementation is more natural this way. - There's less code in each implementation. Matthew Wilcox (Oracle) (19): mm: Return void from various readahead functions mm: Ignore return value of ->readpages mm: Use readahead_control to pass arguments mm: Rearrange readahead loop mm: Remove 'page_offset' from readahead loop mm: rename readahead loop variable to 'i' mm: Put readahead pages in cache earlier mm: Add readahead address space operation mm: Add page_cache_readahead_limit fs: Convert mpage_readpages to mpage_readahead btrfs: Convert from readpages to readahead erofs: Convert uncompressed files from readpages to readahead erofs: Convert compressed files from readpages to readahead ext4: Convert from readpages to readahead f2fs: Convert from readpages to readahead fuse: Convert from readpages to readahead iomap: Restructure iomap_readpages_actor iomap: Convert from readpages to readahead mm: Use memalloc_nofs_save in readahead path Documentation/filesystems/locking.rst | 6 +- Documentation/filesystems/vfs.rst | 13 ++ drivers/staging/exfat/exfat_super.c | 7 +- fs/block_dev.c | 7 +- fs/btrfs/extent_io.c | 46 ++----- fs/btrfs/extent_io.h | 3 +- fs/btrfs/inode.c | 16 +-- fs/erofs/data.c | 39 ++---- fs/erofs/zdata.c | 29 ++-- fs/ext2/inode.c | 10 +- fs/ext4/ext4.h | 3 +- fs/ext4/inode.c | 23 ++-- fs/ext4/readpage.c | 22 ++- fs/ext4/verity.c | 35 +---- fs/f2fs/data.c | 50 +++---- fs/f2fs/f2fs.h | 5 +- fs/f2fs/verity.c | 35 +---- fs/fat/inode.c | 7 +- fs/fuse/file.c | 46 +++---- fs/gfs2/aops.c | 23 ++-- fs/hpfs/file.c | 7 +- fs/iomap/buffered-io.c | 118 +++++++---------- fs/iomap/trace.h | 2 +- fs/isofs/inode.c | 7 +- fs/jfs/inode.c | 7 +- fs/mpage.c | 38 ++---- fs/nilfs2/inode.c | 15 +-- fs/ocfs2/aops.c | 34 ++--- fs/omfs/file.c | 7 +- fs/qnx6/inode.c | 7 +- fs/reiserfs/inode.c | 8 +- fs/udf/inode.c | 7 +- fs/xfs/xfs_aops.c | 13 +- fs/zonefs/super.c | 7 +- include/linux/fs.h | 2 + include/linux/iomap.h | 3 +- include/linux/mpage.h | 4 +- include/linux/pagemap.h | 90 +++++++++++++ include/trace/events/erofs.h | 6 +- include/trace/events/f2fs.h | 6 +- mm/internal.h | 8 +- mm/migrate.c | 2 +- mm/readahead.c | 184 +++++++++++++++++--------- 43 files changed, 474 insertions(+), 533 deletions(-) base-commit: 11a48a5a18c63fd7621bb050228cebf13566e4d8 -- 2.25.0
