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authorLennart Poettering <lennart@poettering.net>2015-01-14 23:09:02 +0100
committerLennart Poettering <lennart@poettering.net>2015-01-14 23:18:33 +0100
commit30535c16924a3da7b47ea87190d929d617d95c5a (patch)
treea2cd4f490a5a7d71350b31607a690aff42d1077d /src/shared/machine-image.h
parent805e5dda0a01c99d231824e1a9c4a208418bf342 (diff)
nspawn: add file system locks for controlling access to container images
This adds three kinds of file system locks for container images: a) a file system lock next to the actual image, in a .lck file in the same directory the image is located. This lock has the benefit of usually being located on the same NFS share as the image itself, and thus allows locking container images across NFS shares. b) a file system lock in /run, named after st_dev and st_ino of the root of the image. This lock has the advantage that it is unique even if the same image is bind mounted to two different places at the same time, as the ino/dev stays constant for them. c) a file system lock that is only taken when a new disk image is about to be created, that ensures that checking whether the name is already used across the search path, and actually placing the image is not interrupted by other code taking the name. a + b are read-write locks. When a container is booted in read-only mode a read lock is taken, otherwise a write lock. Lock b is always taken after a, to avoid ABBA problems. Lock c is mostly relevant when renaming or cloning images.
Diffstat (limited to 'src/shared/machine-image.h')
-rw-r--r--src/shared/machine-image.h5
1 files changed, 5 insertions, 0 deletions
diff --git a/src/shared/machine-image.h b/src/shared/machine-image.h
index 10e5d0a533..4f41b4f307 100644
--- a/src/shared/machine-image.h
+++ b/src/shared/machine-image.h
@@ -63,3 +63,8 @@ int image_read_only(Image *i, bool b);
const char* image_type_to_string(ImageType t) _const_;
ImageType image_type_from_string(const char *s) _pure_;
+
+bool image_name_is_valid(const char *s) _pure_;
+
+int image_path_lock(const char *path, int operation, LockFile *global, LockFile *local);
+int image_name_lock(const char *name, int operation, LockFile *ret);