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 Thanks, Miklos --- Miklos Szeredi (35): vfs: clean up dedup vfs: add path_open() vfs: optionally don't account file in nr_files 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: readd read_iter ovl: readd write_iter ovl: readd fsync ovl: readd mmap ovl: readd fallocate ovl: readd lsattr/chattr support ovl: readd fiemap ovl: readd O_DIRECT support ovl: readd reflink/copyfile/dedup support vfs: don't open real vfs: add f_op->pre_mmap() ovl: copy-up on MAP_SHARED vfs: simplify dentry_open() Revert "ovl: fix relatime for directories" Revert "vfs: update ovl inode before relatime check" Revert "ovl: fix may_write_real() for overlayfs directories" Revert "ovl: don't allow writing ioctl on lower layer" Revert "vfs: add flags to d_real()" Revert "vfs: do get_write_access() on upper layer of overlayfs" Revert "vfs: make argument of d_real_inode() const" Revert "vfs: add d_real_inode() helper" Partially revert "locks: fix file locking on overlayfs" Revert "fsnotify: support overlayfs" vfs: simplify d_op->d_real() ovl: fix documentation of non-standard behavior Documentation/filesystems/Locking | 4 +- Documentation/filesystems/overlayfs.txt | 64 +++-- Documentation/filesystems/vfs.txt | 25 +- 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 | 66 +---- fs/open.c | 79 +++--- fs/overlayfs/Kconfig | 21 ++ fs/overlayfs/Makefile | 4 +- fs/overlayfs/dir.c | 5 + fs/overlayfs/file.c | 466 ++++++++++++++++++++++++++++++++ fs/overlayfs/inode.c | 52 +++- fs/overlayfs/overlayfs.h | 26 ++ fs/overlayfs/ovl_entry.h | 1 + fs/overlayfs/super.c | 82 +++--- fs/overlayfs/util.c | 20 ++ fs/read_write.c | 90 +++--- fs/xattr.c | 9 +- include/linux/dcache.h | 41 +-- include/linux/fs.h | 32 ++- include/linux/fsnotify.h | 14 +- include/uapi/linux/fs.h | 1 - mm/util.c | 5 + 27 files changed, 831 insertions(+), 375 deletions(-) create mode 100644 fs/overlayfs/file.c -- 2.14.3
