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authorLinus Torvalds <torvalds@linux-foundation.org>2017-05-10 19:03:48 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2017-05-10 19:03:48 +0300
commitb948abf53a381a0c681aadd612e2affba47f62bc (patch)
tree006012adf8876af6fa1bdefa6361a673a9142c83 /Documentation
parenta2e5ad45a9741068f357de4dbff50bb37c233e1b (diff)
parent65f2673832d4647f6d46783d8d745d2b15d090c4 (diff)
downloadlinux-b948abf53a381a0c681aadd612e2affba47f62bc.tar.xz
Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs
Pull overlayfs update from Miklos Szeredi: "The biggest part of this is making st_dev/st_ino on the overlay behave like a normal filesystem (i.e. st_ino doesn't change on copy up, st_dev is the same for all files and directories). Currently this only works if all layers are on the same filesystem, but future work will move the general case towards more sane behavior. There are also miscellaneous fixes, including fixes to handling append-only files. There's a small change in the VFS, but that only has an effect on overlayfs, since otherwise file->f_path.dentry->inode and file_inode(file) are always the same" * 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs: ovl: update documentation w.r.t. constant inode numbers ovl: persistent inode numbers for upper hardlinks ovl: merge getattr for dir and nondir ovl: constant st_ino/st_dev across copy up ovl: persistent inode number for directories ovl: set the ORIGIN type flag ovl: lookup non-dir copy-up-origin by file handle ovl: use an auxiliary var for overlay root entry ovl: store file handle of lower inode on copy up ovl: check if all layers are on the same fs ovl: do not set overlay.opaque on non-dir create ovl: check IS_APPEND() on real upper inode vfs: ftruncate check IS_APPEND() on real upper inode ovl: Use designated initializers ovl: lockdep annotate of nested stacked overlayfs inode lock
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/overlayfs.txt9
1 files changed, 8 insertions, 1 deletions
diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.txt
index 634d03e20c2d..c9e884b52698 100644
--- a/Documentation/filesystems/overlayfs.txt
+++ b/Documentation/filesystems/overlayfs.txt
@@ -21,12 +21,19 @@ from accessing the corresponding object from the original filesystem.
This is most obvious from the 'st_dev' field returned by stat(2).
While directories will report an st_dev from the overlay-filesystem,
-all non-directory objects will report an st_dev from the lower or
+non-directory objects may report an st_dev from the lower filesystem or
upper filesystem that is providing the object. Similarly st_ino will
only be unique when combined with st_dev, and both of these can change
over the lifetime of a non-directory object. Many applications and
tools ignore these values and will not be affected.
+In the special case of all overlay layers on the same underlying
+filesystem, all objects will report an st_dev from the overlay
+filesystem and st_ino from the underlying filesystem. This will
+make the overlay mount more compliant with filesystem scanners and
+overlay objects will be distinguishable from the corresponding
+objects in the original filesystem.
+
Upper and Lower
---------------