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    SubjectRe: [RFC PATCH 11/35] ovl: readd read_iter
    On Thu, Apr 12, 2018 at 6:08 PM, Miklos Szeredi <mszeredi@redhat.com> wrote:
    > Implement stacked reading.
    >

    I couldn't decipher the meaning of "readd" in the subject of this
    and other file ops pacthes??

    > Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
    > ---
    > fs/overlayfs/file.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++
    > 1 file changed, 56 insertions(+)
    >
    > diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
    > index 409b542ff30c..a19429c5965d 100644
    > --- a/fs/overlayfs/file.c
    > +++ b/fs/overlayfs/file.c
    > @@ -9,6 +9,7 @@
    > #include <linux/cred.h>
    > #include <linux/file.h>
    > #include <linux/xattr.h>
    > +#include <linux/uio.h>
    > #include "overlayfs.h"
    >
    > static struct file *ovl_open_realfile(const struct file *file)
    > @@ -129,8 +130,63 @@ static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
    > i_size_read(realinode));
    > }
    >
    > +static void ovl_file_accessed(struct file *file)
    > +{
    > + struct inode *inode = file_inode(file);
    > +
    > + if ((file->f_flags & O_NOATIME) || !ovl_inode_upper(inode))
    > + return;
    > +
    > + ovl_copytimes(inode);
    > + touch_atime(&file->f_path);
    > +}
    > +
    > +static rwf_t ovl_iocb_to_rwf(struct kiocb *iocb)
    > +{
    > + int ifl = iocb->ki_flags;
    > + rwf_t flags = 0;
    > +
    > + if (ifl & IOCB_NOWAIT)
    > + flags |= RWF_NOWAIT;
    > + if (ifl & IOCB_HIPRI)
    > + flags |= RWF_HIPRI;
    > + if (ifl & IOCB_DSYNC)
    > + flags |= RWF_DSYNC;
    > + if (ifl & IOCB_SYNC)
    > + flags |= RWF_SYNC;
    > +
    > + return flags;
    > +}
    > +
    > +static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
    > +{
    > + struct file *file = iocb->ki_filp;
    > + struct fd real;
    > + const struct cred *old_cred;
    > + ssize_t ret;
    > +
    > + if (!iov_iter_count(iter))
    > + return 0;
    > +
    > + ret = ovl_real_file(file, &real);
    > + if (ret)
    > + return ret;
    > +
    > + old_cred = ovl_override_creds(file_inode(file)->i_sb);
    > + ret = vfs_iter_read(real.file, iter, &iocb->ki_pos,
    > + ovl_iocb_to_rwf(iocb));
    > + revert_creds(old_cred);
    > +
    > + ovl_file_accessed(file);
    > +
    > + fdput(real);

    I find it confusing that the name of ovl_real_file() does not suggest it
    may take a reference, so this fdput() looks unbalanced.

    All other ovl_XXX_{real,upper,lower} helpers do not take a reference.
    Perhaps something along the lines of ovl_file_real_fdget().

    Thanks,
    Amir.

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