On Sun, Aug 26, 2018 at 6:25 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
> For an overlayfs file/inode, gage io is operating on the real underlying
> file, so the readahead hints set by fadvise64() should also be set on the
> real underlying file to take affect.
Hmm, how about making this be an f_op?
Would also fix readahead(2), which can be translated to fadvise(...,
POSIX_FADV_WILLNEED).
And possibly be useful for other filesystems, since there are cases
when things are not done through a_ops, yet the filesystem would
benefit from knowing the intentions of the user.
Thanks,
Miklos
>
> Fixes: d1d04ef8572b ("ovl: stack file ops")
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> mm/fadvise.c | 34 ++++++++++++++++++++--------------
> 1 file changed, 20 insertions(+), 14 deletions(-)
>
> diff --git a/mm/fadvise.c b/mm/fadvise.c
> index 2d8376e3c640..d5528343ce77 100644
> --- a/mm/fadvise.c
> +++ b/mm/fadvise.c
> @@ -30,6 +30,7 @@
> int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
> {
> struct fd f = fdget(fd);
> + struct file *file;
> struct inode *inode;
> struct address_space *mapping;
> struct backing_dev_info *bdi;
> @@ -42,13 +43,18 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
> if (!f.file)
> return -EBADF;
>
> - inode = file_inode(f.file);
> + /*
> + * XXX: We need to use file_real() for overlayfs stacked file because
> + * readahead will be operating on the real underlying file/inode.
> + */
> + file = file_real(f.file);
> + inode = file_inode(file);
> if (S_ISFIFO(inode->i_mode)) {
> ret = -ESPIPE;
> goto out;
> }
>
> - mapping = f.file->f_mapping;
> + mapping = file->f_mapping;
> if (!mapping || len < 0) {
> ret = -EINVAL;
> goto out;
> @@ -85,21 +91,21 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
>
> switch (advice) {
> case POSIX_FADV_NORMAL:
> - f.file->f_ra.ra_pages = bdi->ra_pages;
> - spin_lock(&f.file->f_lock);
> - f.file->f_mode &= ~FMODE_RANDOM;
> - spin_unlock(&f.file->f_lock);
> + file->f_ra.ra_pages = bdi->ra_pages;
> + spin_lock(&file->f_lock);
> + file->f_mode &= ~FMODE_RANDOM;
> + spin_unlock(&file->f_lock);
> break;
> case POSIX_FADV_RANDOM:
> - spin_lock(&f.file->f_lock);
> - f.file->f_mode |= FMODE_RANDOM;
> - spin_unlock(&f.file->f_lock);
> + spin_lock(&file->f_lock);
> + file->f_mode |= FMODE_RANDOM;
> + spin_unlock(&file->f_lock);
> break;
> case POSIX_FADV_SEQUENTIAL:
> - f.file->f_ra.ra_pages = bdi->ra_pages * 2;
> - spin_lock(&f.file->f_lock);
> - f.file->f_mode &= ~FMODE_RANDOM;
> - spin_unlock(&f.file->f_lock);
> + file->f_ra.ra_pages = bdi->ra_pages * 2;
> + spin_lock(&file->f_lock);
> + file->f_mode &= ~FMODE_RANDOM;
> + spin_unlock(&file->f_lock);
> break;
> case POSIX_FADV_WILLNEED:
> /* First and last PARTIAL page! */
> @@ -115,7 +121,7 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
> * Ignore return value because fadvise() shall return
> * success even if filesystem can't retrieve a hint,
> */
> - force_page_cache_readahead(mapping, f.file, start_index,
> + force_page_cache_readahead(mapping, file, start_index,
> nrpages);
> break;
> case POSIX_FADV_NOREUSE:
> --
> 2.7.4
>
