ovl: whiteout inode sharing

Share inode with different whiteout files for saving inode and speeding up
delete operation.

If EMLINK is encountered when linking a shared whiteout, create a new one.
In case of any other error, disable sharing for this super block.

Note: ofs->whiteout is protected by inode lock on workdir.

Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 279009d..09faa63 100644 (file)
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -62,35 +62,59 @@ struct dentry *ovl_lookup_temp(struct dentry *workdir)
 }
 
 /* caller holds i_mutex on workdir */
-static struct dentry *ovl_whiteout(struct dentry *workdir)
+static struct dentry *ovl_whiteout(struct ovl_fs *ofs)
 {
        int err;
        struct dentry *whiteout;
+       struct dentry *workdir = ofs->workdir;
        struct inode *wdir = workdir->d_inode;
 
-       whiteout = ovl_lookup_temp(workdir);
-       if (IS_ERR(whiteout))
-               return whiteout;
+       if (!ofs->whiteout) {
+               whiteout = ovl_lookup_temp(workdir);
+               if (IS_ERR(whiteout))
+                       goto out;
 
-       err = ovl_do_whiteout(wdir, whiteout);
-       if (err) {
-               dput(whiteout);
-               whiteout = ERR_PTR(err);
+               err = ovl_do_whiteout(wdir, whiteout);
+               if (err) {
+                       dput(whiteout);
+                       whiteout = ERR_PTR(err);
+                       goto out;
+               }
+               ofs->whiteout = whiteout;
        }
 
+       if (ofs->share_whiteout) {
+               whiteout = ovl_lookup_temp(workdir);
+               if (IS_ERR(whiteout))
+                       goto out;
+
+               err = ovl_do_link(ofs->whiteout, wdir, whiteout);
+               if (!err)
+                       goto out;
+
+               if (err != -EMLINK) {
+                       pr_warn("Failed to link whiteout - disabling whiteout inode sharing(nlink=%u, err=%i)\n",
+                               ofs->whiteout->d_inode->i_nlink, err);
+                       ofs->share_whiteout = false;
+               }
+               dput(whiteout);
+       }
+       whiteout = ofs->whiteout;
+       ofs->whiteout = NULL;
+out:
        return whiteout;
 }
 
 /* Caller must hold i_mutex on both workdir and dir */
-int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
+int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct inode *dir,
                             struct dentry *dentry)
 {
-       struct inode *wdir = workdir->d_inode;
+       struct inode *wdir = ofs->workdir->d_inode;
        struct dentry *whiteout;
        int err;
        int flags = 0;
 
-       whiteout = ovl_whiteout(workdir);
+       whiteout = ovl_whiteout(ofs);
        err = PTR_ERR(whiteout);
        if (IS_ERR(whiteout))
                return err;
@@ -715,6 +739,7 @@ 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 = OVL_FS(dentry->d_sb);
        struct dentry *workdir = ovl_workdir(dentry);
        struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
        struct dentry *upper;
@@ -748,7 +773,7 @@ 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, d_inode(upperdir), upper);
        if (err)
                goto out_d_drop;
 

diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index e00b1ff..76747f5 100644 (file)
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -455,7 +455,7 @@ static inline void ovl_copyflags(struct inode *from, struct inode *to)
 
 /* dir.c */
 extern const struct inode_operations ovl_dir_inode_operations;
-int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
+int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct inode *dir,
                             struct dentry *dentry);
 struct ovl_cattr {
        dev_t rdev;

diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 5762d80..a8f82fb 100644 (file)
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -68,6 +68,7 @@ struct ovl_fs {
        /* Did we take the inuse lock? */
        bool upperdir_locked;
        bool workdir_locked;
+       bool share_whiteout;
        /* Traps in ovl inode cache */
        struct inode *upperdir_trap;
        struct inode *workbasedir_trap;
@@ -77,6 +78,8 @@ struct ovl_fs {
        int xino_mode;
        /* For allocation of non-persistent inode numbers */
        atomic_long_t last_ino;
+       /* Whiteout dentry cache */
+       struct dentry *whiteout;
 };
 
 static inline struct ovl_fs *OVL_FS(struct super_block *sb)

diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 20f5310..a10b21b 100644 (file)
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -1154,7 +1154,7 @@ 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, 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 af69f41..a88a7ba 100644 (file)
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -217,6 +217,7 @@ static void ovl_free_fs(struct ovl_fs *ofs)
        iput(ofs->indexdir_trap);
        iput(ofs->workdir_trap);
        iput(ofs->upperdir_trap);
+       dput(ofs->whiteout);
        dput(ofs->indexdir);
        dput(ofs->workdir);
        if (ofs->workdir_locked)
@@ -1776,6 +1777,9 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
        if (!cred)
                goto out_err;
 
+       /* Is there a reason anyone would want not to share whiteouts? */
+       ofs->share_whiteout = true;
+
        ofs->config.index = ovl_index_def;
        ofs->config.nfs_export = ovl_nfs_export_def;
        ofs->config.xino = ovl_xino_def();

diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 36b6078..01755bc 100644 (file)
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -707,7 +707,8 @@ static void ovl_cleanup_index(struct dentry *dentry)
                index = NULL;
        } else if (ovl_index_all(dentry->d_sb)) {
                /* Whiteout orphan index to block future open by handle */
-               err = ovl_cleanup_and_whiteout(indexdir, dir, index);
+               err = ovl_cleanup_and_whiteout(OVL_FS(dentry->d_sb),
+                                              dir, index);
        } else {
                /* Cleanup orphan index entries */
                err = ovl_cleanup(dir, index);