Linus recently made the page lock more fair. That means that the old pattern where we returned from ->readpage with the page unlocked and then attempted to re-lock it will send us to the back of the queue for this page's lock. A further benefit is that a synchronous readpage implementation allows us to return an error to someone who might actually care about it. There's no need to SetPageError, but I don't want to learn about how a dozen filesystems handle I/O errors (hint: they're all different), so I have not attempted to change that. Except for iomap. Ideally all filesystems would return from ->readpage with the page Uptodate and Locked, but it's a bit painful to convert all the asynchronous readpage implementations to synchronous. The first 14 filesystems converted are already synchronous. The last two patches convert iomap to synchronous readpage. This patchset is against iomap-for-next. Andrew, it would make merging the THP patchset much easier if you could merge at least the first patch adding AOP_UPDATED_PAGE during the merge window which opens next week. Matthew Wilcox (Oracle) (16): mm: Add AOP_UPDATED_PAGE return value mm: Inline wait_on_page_read into its one caller 9p: Tell the VFS that readpage was synchronous afs: Tell the VFS that readpage was synchronous ceph: Tell the VFS that readpage was synchronous cifs: Tell the VFS that readpage was synchronous cramfs: Tell the VFS that readpage was synchronous ecryptfs: Tell the VFS that readpage was synchronous fuse: Tell the VFS that readpage was synchronous hostfs: Tell the VFS that readpage was synchronous jffs2: Tell the VFS that readpage was synchronous ubifs: Tell the VFS that readpage was synchronous udf: Tell the VFS that readpage was synchronous vboxsf: Tell the VFS that readpage was synchronous iomap: Inline iomap_iop_set_range_uptodate into its one caller iomap: Make readpage synchronous Documentation/filesystems/locking.rst | 7 +- Documentation/filesystems/vfs.rst | 21 ++++-- fs/9p/vfs_addr.c | 6 +- fs/afs/file.c | 3 +- fs/ceph/addr.c | 9 +-- fs/cifs/file.c | 8 ++- fs/cramfs/inode.c | 5 +- fs/ecryptfs/mmap.c | 11 ++-- fs/fuse/file.c | 2 + fs/hostfs/hostfs_kern.c | 2 + fs/iomap/buffered-io.c | 92 ++++++++++++++------------- fs/jffs2/file.c | 6 +- fs/ubifs/file.c | 16 +++-- fs/udf/file.c | 3 +- fs/vboxsf/file.c | 2 + include/linux/fs.h | 5 ++ mm/filemap.c | 33 +++++----- 17 files changed, 135 insertions(+), 96 deletions(-) -- 2.28.0
