Now each whiteout file will be assigned a new inode. To reduce the
overhead of allocating and freeing inodes in upper fs, creating a
singleton whiteout file under workdir and hardlink all whiteout files
into it.
The effect is obvious: under a KVM VM, the time used for removing the
linux kernel source tree is reduced from 17s to 10s.
Got the idea from aufs4.
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
v3:
* rebased on 4.16-rc3
* add a limitation on the hardlinks of singleton whiteout, and it
can be adjusted by module param singleton_wt_link_max. During
the mount procoess, if the value of limit is less than or equal to 1,
the singleon whiteout will be disabled (suggested by Amir)
* rename ovl_make_singleton_whiteout_nolock() to
ovl_make_singleton_whiteout_locked() (also from Amir)
* check errors more strictly: treat singleton whiteout creation
failure as an error and abort the mount or unlink procedure
* remove unnecessary mnt_want_write() from ovl_make_singleton_whiteout(),
because mnt_want_write() has been invoked by its caller.
* document the lock assertions for newly-added helpers
v2:
* address the comments from Miklos and Amir: handle -EMLINK and -EXDEV
when hard-linking whiteout file to the singleton
* move the singleton whiteout from workbasedir to workdir to simplify
the lock of inodes
v1:
* https://www.spinics.net/lists/linux-unionfs/msg04023.html
---
fs/overlayfs/dir.c | 150 +++++++++++++++++++++++++++++++++++++++++++++--
fs/overlayfs/overlayfs.h | 5 +-
fs/overlayfs/ovl_entry.h | 5 ++
fs/overlayfs/readdir.c | 2 +-
fs/overlayfs/super.c | 5 ++
fs/overlayfs/util.c | 4 +-
6 files changed, 161 insertions(+), 10 deletions(-)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 839709c7803a..c87360d22f92 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -24,6 +24,12 @@ module_param_named(redirect_max, ovl_redirect_max, ushort, 0644);
MODULE_PARM_DESC(ovl_redirect_max,
"Maximum length of absolute redirect xattr value");
+static unsigned int ovl_singleton_wt_link_max = 255;
+module_param_named(singleton_whiteout_link_max,
+ ovl_singleton_wt_link_max, uint, 0644);
+MODULE_PARM_DESC(ovl_singleton_wt_link_max,
+ "Maximum hardlinks of a whiteout singleton");
+
int ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
{
int err;
@@ -62,18 +68,149 @@ struct dentry *ovl_lookup_temp(struct dentry *workdir)
return temp;
}
+#define OVL_SINGLETON_WHITEOUT_NAME "whiteout"
+
+/* caller holds write lock (i_rwsem) of dir */
+static int ovl_make_singleton_whiteout_locked(struct ovl_fs *ofs,
+ struct dentry *dir, const char *name)
+{
+ int err = 0;
+ struct inode *inode = d_inode(dir);
+ struct dentry *whiteout;
+
+ whiteout = lookup_one_len(name, dir, strlen(name));
+ if (IS_ERR(whiteout))
+ return PTR_ERR(whiteout);
+
+ if (ovl_is_whiteout(whiteout)) {
+ ofs->whiteout = whiteout;
+ } else if (!whiteout->d_inode) {
+ err = ovl_do_whiteout(inode, whiteout);
+ if (!err)
+ ofs->whiteout = whiteout;
+ else
+ dput(whiteout);
+ } else {
+ /*
+ * fallback to creating new whiteout file if
+ * a non-whiteout file already exists
+ */
+ dput(whiteout);
+ }
+
+ return err;
+}
+
+/*
+ * create a new whiteout file under workdir if it doesn't exist.
+ * If a non-whiteout file already exists, no error will be reported
+ * and the needed whiteout file will be newly created instead of
+ * being linked to a singleton whiteout.
+ */
+int ovl_make_singleton_whiteout(struct ovl_fs *ofs)
+{
+ int err;
+ struct inode *dir;
+
+ /* disable singleton whiteout */
+ if (ovl_singleton_wt_link_max <= 1)
+ return 0;
+
+ dir = d_inode(ofs->workdir);
+ inode_lock_nested(dir, I_MUTEX_PARENT);
+
+ err = ovl_make_singleton_whiteout_locked(ofs, ofs->workdir,
+ OVL_SINGLETON_WHITEOUT_NAME);
+
+ inode_unlock(dir);
+
+ return err;
+}
+
+/*
+ * caller holds i_mutex of workdir to ensure the operations
+ * on the singletion whiteout are serialized.
+ */
+static int ovl_link_to_singleton_whiteout(struct ovl_fs *ofs,
+ struct dentry *whiteout, bool *create_instead)
+{
+ int err;
+ struct inode *wdir = d_inode(ofs->workdir);
+ struct dentry *singleton;
+ bool retried = false;
+
+ *create_instead = false;
+retry:
+ singleton = ofs->whiteout;
+ /* Create a new singletion whiteout when the limit is exceeded */
+ if (1 < ovl_singleton_wt_link_max &&
+ singleton->d_inode->i_nlink >= ovl_singleton_wt_link_max)
+ err = -EMLINK;
+ else
+ err = ovl_do_link(singleton, wdir, whiteout, false);
+
+ if (!err) {
+ goto out;
+ } else if (err == -EMLINK && !retried) {
+ /*
+ * The singleton already has the maximum number of links to it,
+ * so remove the old singleton and create a new one
+ */
+ ofs->whiteout = NULL;
+ err = ovl_do_unlink(wdir, singleton);
+ if (err) {
+ dput(singleton);
+ goto out;
+ }
+
+ dput(singleton);
+ err = ovl_make_singleton_whiteout_locked(ofs, ofs->workdir,
+ OVL_SINGLETON_WHITEOUT_NAME);
+ if (err)
+ goto out;
+
+ retried = true;
+ if (ofs->whiteout)
+ goto retry;
+ else
+ goto out_fallback;
+ } else if (err == -EXDEV) {
+ /*
+ * upper fs may have a project id different than singleton,
+ * so fall back to create whiteout directly
+ */
+ goto out_fallback;
+ } else {
+ goto out;
+ }
+
+out_fallback:
+ *create_instead = true;
+out:
+ return err;
+}
+
/* caller holds i_mutex on workdir */
-static struct dentry *ovl_whiteout(struct dentry *workdir)
+static struct dentry *ovl_whiteout(struct ovl_fs *ofs, struct dentry *workdir)
{
int err;
struct dentry *whiteout;
struct inode *wdir = workdir->d_inode;
+ bool create_instead;
whiteout = ovl_lookup_temp(workdir);
if (IS_ERR(whiteout))
return whiteout;
- err = ovl_do_whiteout(wdir, whiteout);
+ if (workdir == ofs->workdir && ofs->whiteout)
+ err = ovl_link_to_singleton_whiteout(ofs, whiteout,
+ &create_instead);
+ else
+ create_instead = true;
+
+ if (create_instead)
+ err = ovl_do_whiteout(wdir, whiteout);
+
if (err) {
dput(whiteout);
whiteout = ERR_PTR(err);
@@ -83,15 +220,15 @@ static struct dentry *ovl_whiteout(struct dentry *workdir)
}
/* Caller must hold i_mutex on both workdir and dir */
-int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
- struct dentry *dentry)
+int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct dentry *workdir,
+ struct inode *dir, struct dentry *dentry)
{
struct inode *wdir = workdir->d_inode;
struct dentry *whiteout;
int err;
int flags = 0;
- whiteout = ovl_whiteout(workdir);
+ whiteout = ovl_whiteout(ofs, workdir);
err = PTR_ERR(whiteout);
if (IS_ERR(whiteout))
return err;
@@ -621,6 +758,7 @@ static bool ovl_matches_upper(struct dentry *dentry, struct dentry *upper)
static int ovl_remove_and_whiteout(struct dentry *dentry,
struct list_head *list)
{
+ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
struct dentry *workdir = ovl_workdir(dentry);
struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
struct dentry *upper;
@@ -654,7 +792,7 @@ static int ovl_remove_and_whiteout(struct dentry *dentry,
goto out_dput_upper;
}
- err = ovl_cleanup_and_whiteout(workdir, d_inode(upperdir), upper);
+ err = ovl_cleanup_and_whiteout(ofs, workdir, d_inode(upperdir), upper);
if (err)
goto out_d_drop;
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 0df25a9c94bd..d46894598f05 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -343,8 +343,8 @@ static inline void ovl_copyattr(struct inode *from, struct inode *to)
/* dir.c */
extern const struct inode_operations ovl_dir_inode_operations;
struct dentry *ovl_lookup_temp(struct dentry *workdir);
-int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
- struct dentry *dentry);
+int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct dentry *workdir,
+ struct inode *dir, struct dentry *dentry);
struct cattr {
dev_t rdev;
umode_t mode;
@@ -354,6 +354,7 @@ int ovl_create_real(struct inode *dir, struct dentry *newdentry,
struct cattr *attr,
struct dentry *hardlink, bool debug);
int ovl_cleanup(struct inode *dir, struct dentry *dentry);
+int ovl_make_singleton_whiteout(struct ovl_fs *ofs);
/* copy_up.c */
int ovl_copy_up(struct dentry *dentry);
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index bfef6edcc111..5a7929f8a778 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -43,6 +43,11 @@ struct ovl_fs {
struct dentry *workdir;
/* index directory listing overlay inodes by origin file handle */
struct dentry *indexdir;
+ /*
+ * the singleton whiteout file under workdir: all newly created
+ * whiteout files will be linked to it if possible
+ */
+ struct dentry *whiteout;
long namelen;
/* pathnames of lower and upper dirs, for show_options */
struct ovl_config config;
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index c11f5c0906c3..4858ea6e8b99 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -1084,7 +1084,7 @@ int ovl_indexdir_cleanup(struct ovl_fs *ofs)
* Whiteout orphan index to block future open by
* handle after overlay nlink dropped to zero.
*/
- err = ovl_cleanup_and_whiteout(indexdir, dir, index);
+ err = ovl_cleanup_and_whiteout(ofs, indexdir, dir, index);
} else {
/* Cleanup orphan index entries */
err = ovl_cleanup(dir, index);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 9ee37c76091d..0b26523eaf43 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -229,6 +229,7 @@ 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);
@@ -961,6 +962,10 @@ static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath)
if (!ofs->workdir)
goto out;
+ err = ovl_make_singleton_whiteout(ofs);
+ if (err < 0)
+ goto out;
+
/*
* Upper should support d_type, else whiteouts are visible. Given
* workdir and upper are on same fs, we can do iterate_dir() on
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 930784a26623..4b8bbb63bcec 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -533,8 +533,10 @@ static void ovl_cleanup_index(struct dentry *dentry)
if (IS_ERR(index)) {
index = NULL;
} else if (ovl_index_all(dentry->d_sb)) {
+ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+
/* Whiteout orphan index to block future open by handle */
- err = ovl_cleanup_and_whiteout(indexdir, dir, index);
+ err = ovl_cleanup_and_whiteout(ofs, indexdir, dir, index);
} else {
/* Cleanup orphan index entries */
err = ovl_cleanup(dir, index);
--
2.13.6
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