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authorAmir Goldstein <amir73il@gmail.com>2023-06-15 13:22:28 +0200
committerChristian Brauner <brauner@kernel.org>2023-06-19 18:16:38 +0200
commit62d53c4a1dfe347bd87ede46ffad38c9a3870338 (patch)
tree50bf37201de8a425c8e4cc23b1be69bde2e4b6eb /fs/open.c
parentfs: move kmem_cache_zalloc() into alloc_empty_file*() helpers (diff)
downloadlinux-62d53c4a1dfe347bd87ede46ffad38c9a3870338.tar.xz
linux-62d53c4a1dfe347bd87ede46ffad38c9a3870338.zip
fs: use backing_file container for internal files with "fake" f_path
Overlayfs uses open_with_fake_path() to allocate internal kernel files, with a "fake" path - whose f_path is not on the same fs as f_inode. Allocate a container struct backing_file for those internal files, that is used to hold the "fake" ovl path along with the real path. backing_file_real_path() can be used to access the stored real path. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Message-Id: <20230615112229.2143178-5-amir73il@gmail.com> Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs/open.c')
-rw-r--r--fs/open.c45
1 files changed, 33 insertions, 12 deletions
diff --git a/fs/open.c b/fs/open.c
index 322e017bf480..81186b277815 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1149,23 +1149,44 @@ struct file *kernel_file_open(const struct path *path, int flags,
}
EXPORT_SYMBOL_GPL(kernel_file_open);
-struct file *open_with_fake_path(const struct path *path, int flags,
- struct inode *inode, const struct cred *cred)
+/**
+ * backing_file_open - open a backing file for kernel internal use
+ * @path: path of the file to open
+ * @flags: open flags
+ * @path: path of the backing file
+ * @cred: credentials for open
+ *
+ * Open a backing file for a stackable filesystem (e.g., overlayfs).
+ * @path may be on the stackable filesystem and backing inode on the
+ * underlying filesystem. In this case, we want to be able to return
+ * the @real_path of the backing inode. This is done by embedding the
+ * returned file into a container structure that also stores the path of
+ * the backing inode on the underlying filesystem, which can be
+ * retrieved using backing_file_real_path().
+ */
+struct file *backing_file_open(const struct path *path, int flags,
+ const struct path *real_path,
+ const struct cred *cred)
{
- struct file *f = alloc_empty_file_noaccount(flags, cred);
- if (!IS_ERR(f)) {
- int error;
+ struct file *f;
+ int error;
- f->f_path = *path;
- error = do_dentry_open(f, inode, NULL);
- if (error) {
- fput(f);
- f = ERR_PTR(error);
- }
+ f = alloc_empty_backing_file(flags, cred);
+ if (IS_ERR(f))
+ return f;
+
+ f->f_path = *path;
+ path_get(real_path);
+ *backing_file_real_path(f) = *real_path;
+ error = do_dentry_open(f, d_inode(real_path->dentry), NULL);
+ if (error) {
+ fput(f);
+ f = ERR_PTR(error);
}
+
return f;
}
-EXPORT_SYMBOL(open_with_fake_path);
+EXPORT_SYMBOL_GPL(backing_file_open);
#define WILL_CREATE(flags) (flags & (O_CREAT | __O_TMPFILE))
#define O_PATH_FLAGS (O_DIRECTORY | O_NOFOLLOW | O_PATH | O_CLOEXEC)