Now each whiteout file will be assigned a new inode. To reduce the
overhead of allocating and freeing inodes in upper fs, creating a
whiteout file under workbasedir and hardlink all whiteout files into it.
The effect is obvious: under my VM, the time used for removing the
linux kernel source tree will be reduced from 17s to 10s.
Got the idea from autofs.
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
fs/overlayfs/dir.c | 13 +++++++++++-
fs/overlayfs/ovl_entry.h | 5 +++++
fs/overlayfs/super.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++-
3 files changed, 68 insertions(+), 2 deletions(-)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index f9788bc..ef02477 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -62,11 +62,19 @@ struct dentry *ovl_lookup_temp(struct dentry *workdir)
return temp;
}
+static inline struct dentry *ovl_singleton_whiteout(struct dentry *dentry)
+{
+ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+
+ return ofs->whiteout;
+}
+
/* caller holds i_mutex on workdir */
static struct dentry *ovl_whiteout(struct dentry *workdir,
struct dentry *dentry)
{
int err;
+ struct dentry *singleton = ovl_singleton_whiteout(dentry);
struct dentry *whiteout;
struct inode *wdir = workdir->d_inode;
@@ -74,7 +82,10 @@ static struct dentry *ovl_whiteout(struct dentry *workdir,
if (IS_ERR(whiteout))
return whiteout;
- err = ovl_do_whiteout(wdir, whiteout);
+ if (singleton)
+ err = ovl_do_link(singleton, wdir, whiteout, false);
+ else
+ err = ovl_do_whiteout(wdir, whiteout);
if (err) {
dput(whiteout);
whiteout = ERR_PTR(err);
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 9d0bc03..c435538 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -40,6 +40,11 @@ struct ovl_fs {
struct dentry *workdir;
/* index directory listing overlay inodes by origin file handle */
struct dentry *indexdir;
+ /*
+ * the singleton whiteout file under workbasedir
+ * all newly created whiteout files will be linked to it
+ */
+ struct dentry *whiteout;
long namelen;
/* pathnames of lower and upper dirs, for show_options */
struct ovl_config config;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 76440fe..16a7d7f 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -223,6 +223,7 @@ static void ovl_free_fs(struct ovl_fs *ofs)
unsigned i;
dput(ofs->indexdir);
+ dput(ofs->whiteout);
dput(ofs->workdir);
if (ofs->workdir_locked)
ovl_inuse_unlock(ofs->workbasedir);
@@ -509,6 +510,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
#define OVL_WORKDIR_NAME "work"
#define OVL_INDEXDIR_NAME "index"
+#define OVL_WHITEOUT_FILE_NAME "whiteout"
static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
const char *name, bool persist)
@@ -1023,6 +1025,48 @@ static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
return err;
}
+/*
+ * create a new whiteout file under workbasedir if it doesn't exist.
+ * If a non-whiteout file has existed, the singleton whiteout will
+ * not be created.
+ */
+static int ovl_make_singleton_whiteout(struct ovl_fs *ofs, const char *name)
+{
+ int err = 0;
+ struct vfsmount *mnt = ofs->upper_mnt;
+ struct inode *dir = d_inode(ofs->workbasedir);
+ struct dentry *whiteout;
+
+ err = mnt_want_write(mnt);
+ if (err)
+ return err;
+
+ inode_lock_nested(dir, I_MUTEX_PARENT);
+
+ whiteout = lookup_one_len(name, ofs->workbasedir, strlen(name));
+ if (!IS_ERR(whiteout)) {
+ if (ovl_is_whiteout(whiteout)) {
+ ofs->whiteout = whiteout;
+ } else if (!whiteout->d_inode) {
+ err = ovl_do_whiteout(dir, whiteout);
+ if (!err)
+ ofs->whiteout = whiteout;
+ else
+ dput(whiteout);
+ } else {
+ dput(whiteout);
+ ofs->whiteout = NULL;
+ }
+ } else {
+ err = PTR_ERR(whiteout);
+ }
+
+ inode_unlock(dir);
+ mnt_drop_write(mnt);
+
+ return err;
+}
+
static int ovl_get_indexdir(struct ovl_fs *ofs, struct ovl_entry *oe,
struct path *upperpath)
{
@@ -1234,8 +1278,14 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
if (err)
goto out_err;
- if (!ofs->workdir)
+ if (ofs->workdir) {
+ err = ovl_make_singleton_whiteout(ofs,
+ OVL_WHITEOUT_FILE_NAME);
+ if (err)
+ goto out_err;
+ } else {
sb->s_flags |= SB_RDONLY;
+ }
sb->s_stack_depth = ofs->upper_mnt->mnt_sb->s_stack_depth;
sb->s_time_gran = ofs->upper_mnt->mnt_sb->s_time_gran;
--
2.9.5
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