Up till now overlayfs didn't stack regular file operations. Instead, when a file was opened on an overlay, the file from one of the underlying layers would be opened and any file operations performed would directly go to the underlying file on a real filesystem. This works well mostly, but various hacks were added to the VFS to work around issues with this: - d_path() and friends - relatime handling - file locking - fsnotify - writecount handling There are also issues that are unresolved before this patchset: - ioctl's that need write access but can be performed on a O_RDONLY fd - ro/rw inconsistency: file on lower layer opened for read-only will return stale data on read after copy-up and modification - ro/rw inconsistency for mmap: file on lower layer mapped shared will contain stale data after copy-up and modification This patch series reverts the VFS hacks (with the exception of d_path) and fixes the unresoved issues. We need to keep d_path related hacks, because memory maps are still not stacked, yet d_path() should keep working on vma->vm_file->f_path. No regressions were observed after running various test suites (xfstests, ltp, unionmount-testsuite, pjd-fstest). Performance impact of stacking was found to be minimal. Memory use for open overlay files increases by about 256bytes or 12%. Git tree is here: git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git overlayfs-rorw --- Miklos Szeredi (39): vfs: dedpue: return loff_t vfs: dedupe: rationalize args vfs: dedupe: extract helper for a single dedup vfs: add path_open() vfs: optionally don't account file in nr_files vfs: add f_op->pre_mmap() vfs: export vfs_ioctl() to modules vfs: export vfs_dedupe_file_range_one() to modules ovl: copy up times ovl: copy up inode flags Revert "Revert "ovl: get_write_access() in truncate"" ovl: copy up file size as well ovl: deal with overlay files in ovl_d_real() ovl: stack file ops ovl: add helper to return real file ovl: add ovl_read_iter() ovl: add ovl_write_iter() ovl: add ovl_fsync() ovl: add ovl_mmap() ovl: add ovl_fallocate() ovl: add lsattr/chattr support ovl: add ovl_fiemap() ovl: add O_DIRECT support ovl: add reflink/copyfile/dedup support vfs: don't open real ovl: copy-up on MAP_SHARED ovl: obsolete "check_copy_up" module option ovl: fix documentation of non-standard behavior vfs: simplify dentry_open() Revert "ovl: fix may_write_real() for overlayfs directories" Revert "ovl: don't allow writing ioctl on lower layer" vfs: fix freeze protection in mnt_want_write_file() for overlayfs Revert "ovl: fix relatime for directories" Revert "vfs: update ovl inode before relatime check" Revert "vfs: add flags to d_real()" Revert "vfs: do get_write_access() on upper layer of overlayfs" Partially revert "locks: fix file locking on overlayfs" Revert "fsnotify: support overlayfs" vfs: remove open_flags from d_real() Documentation/filesystems/Locking | 4 +- Documentation/filesystems/overlayfs.txt | 60 ++-- Documentation/filesystems/vfs.txt | 19 +- fs/btrfs/ctree.h | 5 +- fs/btrfs/ioctl.c | 7 +- fs/file_table.c | 13 +- fs/inode.c | 46 +-- fs/internal.h | 17 +- fs/ioctl.c | 1 + fs/locks.c | 20 +- fs/namei.c | 2 +- fs/namespace.c | 69 +---- fs/ocfs2/file.c | 10 +- fs/open.c | 74 ++--- fs/overlayfs/Kconfig | 21 ++ fs/overlayfs/Makefile | 4 +- fs/overlayfs/copy_up.c | 30 +- fs/overlayfs/dir.c | 31 +- fs/overlayfs/file.c | 509 ++++++++++++++++++++++++++++++++ fs/overlayfs/inode.c | 63 +++- fs/overlayfs/overlayfs.h | 21 +- fs/overlayfs/ovl_entry.h | 1 + fs/overlayfs/super.c | 65 ++-- fs/overlayfs/util.c | 11 +- fs/read_write.c | 91 +++--- fs/xattr.c | 9 +- fs/xfs/xfs_file.c | 8 +- include/linux/dcache.h | 15 +- include/linux/fs.h | 32 +- include/linux/fsnotify.h | 14 +- include/uapi/linux/fs.h | 1 - mm/util.c | 5 + 32 files changed, 898 insertions(+), 380 deletions(-) create mode 100644 fs/overlayfs/file.c -- 2.14.3
