ovl: copy up regular file using O_TMPFILE

In preparation for concurrent copy up, implement copy up
of regular file as O_TMPFILE that is linked to upperdir
instead of a file in workdir that is moved to upperdir.

Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 01e332725e94dae0ac658b80f5363b61550e3833..6e39e90b560523350b1eb01dc451a3f49ddcaacf 100644 (file)
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -20,6 +20,7 @@
 #include <linux/fdtable.h>
 #include <linux/ratelimit.h>
 #include "overlayfs.h"
+#include "ovl_entry.h"
 
 #define OVL_COPY_UP_CHUNK_SIZE (1 << 20)
 
@@ -233,7 +234,7 @@ int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat)
 static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
                              struct dentry *dentry, struct path *lowerpath,
                              struct kstat *stat, const char *link,
-                             struct kstat *pstat)
+                             struct kstat *pstat, bool tmpfile)
 {
        struct inode *wdir = workdir->d_inode;
        struct inode *udir = upperdir->d_inode;
@@ -263,12 +264,17 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
        if (new_creds)
                old_creds = override_creds(new_creds);
 
-       temp = ovl_lookup_temp(workdir, dentry);
+       if (tmpfile)
+               temp = ovl_do_tmpfile(upperdir, stat->mode);
+       else
+               temp = ovl_lookup_temp(workdir, dentry);
        err = PTR_ERR(temp);
        if (IS_ERR(temp))
                goto out1;
 
-       err = ovl_create_real(wdir, temp, &cattr, NULL, true);
+       err = 0;
+       if (!tmpfile)
+               err = ovl_create_real(wdir, temp, &cattr, NULL, true);
 
        if (new_creds) {
                revert_creds(old_creds);
@@ -300,11 +306,14 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
        if (err)
                goto out_cleanup;
 
-       err = ovl_do_rename(wdir, temp, udir, upper, 0);
+       if (tmpfile)
+               err = ovl_do_link(temp, udir, upper, true);
+       else
+               err = ovl_do_rename(wdir, temp, udir, upper, 0);
        if (err)
                goto out_cleanup;
 
-       newdentry = dget(temp);
+       newdentry = dget(tmpfile ? upper : temp);
        ovl_dentry_update(dentry, newdentry);
        ovl_inode_update(d_inode(dentry), d_inode(newdentry));
 
@@ -318,7 +327,8 @@ out:
        return err;
 
 out_cleanup:
-       ovl_cleanup(wdir, temp);
+       if (!tmpfile)
+               ovl_cleanup(wdir, temp);
        goto out2;
 }
 
@@ -342,6 +352,9 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
        struct dentry *lowerdentry = lowerpath->dentry;
        struct dentry *upperdir;
        const char *link = NULL;
+       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+       /* Should we copyup with O_TMPFILE or with workdir? */
+       bool tmpfile = S_ISREG(stat->mode) && ofs->tmpfile;
 
        if (WARN_ON(!workdir))
                return -EROFS;
@@ -373,7 +386,7 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
        }
 
        err = ovl_copy_up_locked(workdir, upperdir, dentry, lowerpath,
-                                stat, link, &pstat);
+                                stat, link, &pstat, tmpfile);
 out_unlock:
        unlock_rename(workdir, upperdir);
        do_delayed_call(&done);