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/ v5 switches 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. This version deletes a lot more lines than previous versions of the patch -- we're net -97 lines instead of -17 with v4. It'll be even more when we can finish the conversion and remove all the ->readpages support code, including read_cache_pages(). Also new in v5 is patch 5 which adds page_cache_readahead_limit() and converts ext4 and f2fs to use it for their Merkel trees. Matthew Wilcox (Oracle) (13): mm: Fix the return type of __do_page_cache_readahead mm: Ignore return value of ->readpages 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: Convert from readpages to readahead 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 | 48 +++------ 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 | 103 ++++++------------- 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 | 84 +++++++++++++++ include/trace/events/erofs.h | 6 +- include/trace/events/f2fs.h | 6 +- mm/internal.h | 2 +- mm/migrate.c | 2 +- mm/readahead.c | 143 ++++++++++++++++---------- 43 files changed, 422 insertions(+), 519 deletions(-) -- 2.25.0