On Mon, May 7, 2018 at 8:40 PM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote:
> 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@xxxxxxxxxx>
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
except one nit
> ---
> 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);
Instead of changing all those call sites, use a wrapper
ovl_real_fdget(file, real) => ovl_real_fdget_metacopy(file, real, false)
and use ovl_real_fdget_metacopy() directly only when you want
the metacopy file.
Thanks,
Amir.
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