[RFC PATCH v2 1/2] ovl: Define D_REAL_FILEDATA for d_real to return dentry with data

Stefan Berger
2024-04-22T15:07:19Z

Define D_REAL_FILEDATA which is to be used as a parameter for d_real()
to return the dentry that is holding the file data, which is either the
upper or the lower denry. The caller is expected to call d_real() again
on the returned dentry to get to lower layers of a stacked filesystem,
if available. This allows a caller to get all dentries involved in hold
a file's data and iterate through the layers.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
fs/overlayfs/super.c | 6 ++++++
include/linux/dcache.h | 1 +
2 files changed, 7 insertions(+)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 06a231970cb5..f466ad89b005 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -36,6 +36,7 @@ static struct dentry *ovl_d_real(struct dentry *dentry, enum d_real_type type)
switch (type) {
case D_REAL_DATA:
case D_REAL_METADATA:
+ case D_REAL_FILEDATA:
break;
default:
goto bug;
@@ -47,6 +48,11 @@ static struct dentry *ovl_d_real(struct dentry *dentry, enum d_real_type type)
}

upper = ovl_dentry_upper(dentry);
+ if (type == D_REAL_FILEDATA) {
+ if (ovl_has_upperdata(d_inode(dentry)))
+ return upper;
+ return ovl_dentry_lower(dentry);
+ }
if (upper && (type == D_REAL_METADATA ||
ovl_has_upperdata(d_inode(dentry))))
return upper;
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index bf53e3894aae..e4e54fb2cf4e 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -128,6 +128,7 @@ enum dentry_d_lock_class
enum d_real_type {
D_REAL_DATA,
D_REAL_METADATA,
+ D_REAL_FILEDATA,
};

struct dentry_operations {
--
2.43.0