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ovl: defer upper dir lock to tempfile link
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On copy up of regular file using an O_TMPFILE, lock upper dir only
before linking the tempfile in place.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Amir Goldstein authored and Miklos Szeredi committed Jul 4, 2017
1 parent b9ac5c2 commit 15932c4
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Showing 2 changed files with 38 additions and 30 deletions.
67 changes: 38 additions & 29 deletions fs/overlayfs/copy_up.c
Original file line number Diff line number Diff line change
Expand Up @@ -316,6 +316,35 @@ static int ovl_set_origin(struct dentry *dentry, struct dentry *lower,
return err;
}

static int ovl_install_temp(struct dentry *workdir, struct dentry *upperdir,
struct dentry *dentry,
struct dentry *temp, struct kstat *pstat,
bool tmpfile, struct dentry **newdentry)
{
int err;
struct dentry *upper;
struct inode *udir = d_inode(upperdir);

upper = lookup_one_len(dentry->d_name.name, upperdir,
dentry->d_name.len);
if (IS_ERR(upper))
return PTR_ERR(upper);

if (tmpfile)
err = ovl_do_link(temp, udir, upper, true);
else
err = ovl_do_rename(d_inode(workdir), temp, udir, upper, 0);

/* Restore timestamps on parent (best effort) */
if (!err) {
ovl_set_timestamps(upperdir, pstat);
*newdentry = dget(tmpfile ? upper : temp);
}
dput(upper);

return err;
}

static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
struct dentry *dentry, struct path *lowerpath,
struct kstat *stat, const char *link,
Expand All @@ -324,7 +353,6 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
struct inode *wdir = workdir->d_inode;
struct inode *udir = upperdir->d_inode;
struct dentry *newdentry = NULL;
struct dentry *upper = NULL;
struct dentry *temp = NULL;
int err;
const struct cred *old_creds = NULL;
Expand Down Expand Up @@ -371,16 +399,7 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
BUG_ON(upperpath.dentry != NULL);
upperpath.dentry = temp;

if (tmpfile) {
inode_unlock(udir);
err = ovl_copy_up_data(lowerpath, &upperpath,
stat->size);
inode_lock_nested(udir, I_MUTEX_PARENT);
} else {
err = ovl_copy_up_data(lowerpath, &upperpath,
stat->size);
}

err = ovl_copy_up_data(lowerpath, &upperpath, stat->size);
if (err)
goto out_cleanup;
}
Expand Down Expand Up @@ -408,29 +427,21 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir,
goto out_cleanup;
}

upper = lookup_one_len(dentry->d_name.name, upperdir,
dentry->d_name.len);
if (IS_ERR(upper)) {
err = PTR_ERR(upper);
upper = NULL;
goto out_cleanup;
if (tmpfile) {
inode_lock_nested(udir, I_MUTEX_PARENT);
err = ovl_install_temp(workdir, upperdir, dentry, temp, pstat,
tmpfile, &newdentry);
inode_unlock(udir);
} else {
err = ovl_install_temp(workdir, upperdir, dentry, temp, pstat,
tmpfile, &newdentry);
}

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(tmpfile ? upper : temp);
ovl_inode_update(d_inode(dentry), newdentry);

/* Restore timestamps on parent (best effort) */
ovl_set_timestamps(upperdir, pstat);
out:
dput(temp);
dput(upper);
return err;

out_cleanup:
Expand Down Expand Up @@ -496,10 +507,8 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
goto out_done;
}

inode_lock_nested(upperdir->d_inode, I_MUTEX_PARENT);
err = ovl_copy_up_locked(workdir, upperdir, dentry, lowerpath,
stat, link, &pstat, true);
inode_unlock(upperdir->d_inode);
ovl_copy_up_end(dentry);
goto out_done;
}
Expand Down
1 change: 0 additions & 1 deletion fs/overlayfs/util.c
Original file line number Diff line number Diff line change
Expand Up @@ -236,7 +236,6 @@ void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
{
struct inode *upperinode = d_inode(upperdentry);

WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
WARN_ON(OVL_I(inode)->__upperdentry);

/*
Expand Down

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