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Subject[RFC PATCH 00/35] overlayfs: stack file operations
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

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:// overlayfs-rorw


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


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