[PATCH v3 01/16] ovl: store path type in dentry

Amir Goldstein
2017-04-26T21:35:11Z

We would like to add more state info to ovl_entry soon (for const ino)
and this state info would be added as type flags.

Store the type value in ovl_entry and update the UPPER and MERGE type
flags when needed, so ovl_path_type() just returns the stored value.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/overlayfs/namei.c | 1 +
fs/overlayfs/overlayfs.h | 1 +
fs/overlayfs/ovl_entry.h | 3 +++
fs/overlayfs/super.c | 1 +
fs/overlayfs/util.c | 30 ++++++++++++++++++++++++------
5 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index b8b0778..8788fd7 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -338,6 +338,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
kfree(stack);
kfree(d.redirect);
dentry->d_fsdata = oe;
+ ovl_update_type(dentry, d.is_dir);
d_add(dentry, inode);

return NULL;
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 741dc0b..e90a548 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -155,6 +155,7 @@ struct ovl_entry *ovl_alloc_entry(unsigned int numlower);
bool ovl_dentry_remote(struct dentry *dentry);
bool ovl_dentry_weird(struct dentry *dentry);
enum ovl_path_type ovl_path_type(struct dentry *dentry);
+enum ovl_path_type ovl_update_type(struct dentry *dentry, bool is_dir);
void ovl_path_upper(struct dentry *dentry, struct path *path);
void ovl_path_lower(struct dentry *dentry, struct path *path);
enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path);
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 59614fa..293be5f 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -31,6 +31,8 @@ struct ovl_fs {
wait_queue_head_t copyup_wq;
};

+enum ovl_path_type;
+
/* private information held for every overlayfs dentry */
struct ovl_entry {
struct dentry *__upperdentry;
@@ -44,6 +46,7 @@ struct ovl_entry {
};
struct rcu_head rcu;
};
+ enum ovl_path_type __type;
unsigned numlower;
struct path lowerstack[];
};
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index c072a0c..671bac0 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -961,6 +961,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
kfree(stack);

root_dentry->d_fsdata = oe;
+ ovl_update_type(root_dentry, true);

realinode = d_inode(ovl_dentry_real(root_dentry));
ovl_inode_init(d_inode(root_dentry), realinode, !!upperpath.dentry);
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 8a1e24a..bbd6074 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -70,21 +70,38 @@ bool ovl_dentry_weird(struct dentry *dentry)
enum ovl_path_type ovl_path_type(struct dentry *dentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
- enum ovl_path_type type = 0;
+ enum ovl_path_type type = oe->__type;

- if (oe->__upperdentry) {
- type = __OVL_PATH_UPPER;
+ /* Matches smp_wmb() in ovl_update_type() */
+ smp_rmb();
+ return type;
+}
+
+enum ovl_path_type ovl_update_type(struct dentry *dentry, bool is_dir)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+ enum ovl_path_type type = oe->__type;

+ /* Update UPPER/MERGE flags and preserve the rest */
+ type &= ~(__OVL_PATH_UPPER | __OVL_PATH_MERGE);
+ if (oe->__upperdentry) {
+ type |= __OVL_PATH_UPPER;
/*
- * Non-dir dentry can hold lower dentry from previous
- * location.
+ * Non-dir dentry can hold lower dentry from before
+ * copy-up.
*/
- if (oe->numlower && d_is_dir(dentry))
+ if (oe->numlower && is_dir)
type |= __OVL_PATH_MERGE;
} else {
if (oe->numlower > 1)
type |= __OVL_PATH_MERGE;
}
+ /*
+ * Make sure type is consistent with __upperdentry before making it
+ * visible to ovl_path_type().
+ */
+ smp_wmb();
+ oe->__type = type;
return type;
}

@@ -220,6 +237,7 @@ void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
*/
smp_wmb();
oe->__upperdentry = upperdentry;
+ ovl_update_type(dentry, d_is_dir(dentry));
}

void ovl_inode_init(struct inode *inode, struct inode *realinode, bool is_upper)
--
2.7.4