[PATCH v15 17/30] ovl: Open file with data except for the case of fsync

[Vivek Goyal <vgoyal@redhat.com>]

ovl_open() should open file which contains data and not open metacopy
inode. With the introduction of metacopy inodes, with current implementaion
we will end up opening metacopy inode as well.

But there can be certain circumstances like ovl_fsync() where we
want to allow opening a metacopy inode instead.

Hence, change ovl_open_realfile() and ovl_open_real() and add extra
parameter which specifies whether to allow opening metacopy inode or not.
If this parameter is false, we look for data inode and open that.

This should allow covering both the cases.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 fs/overlayfs/file.c | 49 +++++++++++++++++++++++++++++++++----------------
 1 file changed, 33 insertions(+), 16 deletions(-)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index a60734ec89ec..885151e8d0cb 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -14,22 +14,32 @@
 #include <linux/uio.h>
 #include "overlayfs.h"
 
-static struct file *ovl_open_realfile(const struct file *file)
+static struct file *ovl_open_realfile(const struct file *file,
+				      bool allow_metacopy)
 {
 	struct inode *inode = file_inode(file);
 	struct inode *upperinode = ovl_inode_upper(inode);
-	struct inode *realinode = upperinode ?: ovl_inode_lower(inode);
+	struct inode *realinode;
 	struct file *realfile;
+	bool upperopen = false;
 	const struct cred *old_cred;
 
+	if (upperinode && (allow_metacopy || ovl_has_upperdata(inode))) {
+		realinode = upperinode;
+		upperopen = true;
+	} else {
+		realinode = allow_metacopy ? ovl_inode_lower(inode) :
+				 ovl_inode_lowerdata(inode);
+	}
 	old_cred = ovl_override_creds(inode->i_sb);
 	realfile = path_open(&file->f_path, file->f_flags | O_NOATIME,
 			     realinode, current_cred(), false);
 	revert_creds(old_cred);
 
 	pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
-		 file, file, upperinode ? 'u' : 'l', file->f_flags,
-		 realfile, IS_ERR(realfile) ? 0 : realfile->f_flags);
+		 file, file, upperopen ? 'u' : 'l',
+		 file->f_flags, realfile,
+		 IS_ERR(realfile) ? 0 : realfile->f_flags);
 
 	return realfile;
 }
@@ -72,17 +82,24 @@ static int ovl_change_flags(struct file *file, unsigned int flags)
 	return 0;
 }
 
-static int ovl_real_fdget(const struct file *file, struct fd *real)
+static int ovl_real_fdget(const struct file *file, struct fd *real,
+			  bool allow_metacopy)
 {
 	struct inode *inode = file_inode(file);
+	struct inode *realinode;
 
 	real->flags = 0;
 	real->file = file->private_data;
 
+	if (allow_metacopy)
+		realinode = ovl_inode_real(inode);
+	else
+		realinode = ovl_inode_realdata(inode);
+
 	/* Has it been copied up since we'd opened it? */
-	if (unlikely(file_inode(real->file) != ovl_inode_real(inode))) {
+	if (unlikely(file_inode(real->file) != realinode)) {
 		real->flags = FDPUT_FPUT;
-		real->file = ovl_open_realfile(file);
+		real->file = ovl_open_realfile(file, allow_metacopy);
 
 		return PTR_ERR_OR_ZERO(real->file);
 	}
@@ -107,7 +124,7 @@ static int ovl_open(struct inode *inode, struct file *file)
 	/* No longer need these flags, so don't pass them on to underlying fs */
 	file->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 
-	realfile = ovl_open_realfile(file);
+	realfile = ovl_open_realfile(file, false);
 	if (IS_ERR(realfile))
 		return PTR_ERR(realfile);
 
@@ -184,7 +201,7 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 	if (!iov_iter_count(iter))
 		return 0;
 
-	ret = ovl_real_fdget(file, &real);
+	ret = ovl_real_fdget(file, &real, false);
 	if (ret)
 		return ret;
 
@@ -218,7 +235,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 	if (ret)
 		goto out_unlock;
 
-	ret = ovl_real_fdget(file, &real);
+	ret = ovl_real_fdget(file, &real, false);
 	if (ret)
 		goto out_unlock;
 
@@ -244,7 +261,7 @@ static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 	const struct cred *old_cred;
 	int ret;
 
-	ret = ovl_real_fdget(file, &real);
+	ret = ovl_real_fdget(file, &real, true);
 	if (ret)
 		return ret;
 
@@ -283,7 +300,7 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
 	const struct cred *old_cred;
 	int ret;
 
-	ret = ovl_real_fdget(file, &real);
+	ret = ovl_real_fdget(file, &real, false);
 	if (ret)
 		return ret;
 
@@ -311,7 +328,7 @@ static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len
 	const struct cred *old_cred;
 	int ret;
 
-	ret = ovl_real_fdget(file, &real);
+	ret = ovl_real_fdget(file, &real, false);
 	if (ret)
 		return ret;
 
@@ -334,7 +351,7 @@ static long ovl_real_ioctl(struct file *file, unsigned int cmd,
 	const struct cred *old_cred;
 	long ret;
 
-	ret = ovl_real_fdget(file, &real);
+	ret = ovl_real_fdget(file, &real, false);
 	if (ret)
 		return ret;
 
@@ -418,11 +435,11 @@ static s64 ovl_copyfile(struct file *file_in, loff_t pos_in,
 	const struct cred *old_cred;
 	s64 ret;
 
-	ret = ovl_real_fdget(file_out, &real_out);
+	ret = ovl_real_fdget(file_out, &real_out, false);
 	if (ret)
 		return ret;
 
-	ret = ovl_real_fdget(file_in, &real_in);
+	ret = ovl_real_fdget(file_in, &real_in, false);
 	if (ret) {
 		fdput(real_out);
 		return ret;
-- 
2.13.6