On Sun, Jan 15, 2017 at 2:57 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
> Now that copy up of regular file is done using O_TMPFILE,
> we don't need to hold rename_lock throughout copy up.
>
> Use the copy up waitqueue to synchronize concurrent copy up
> of the same file. Different regular files can be copied up
> concurrently.
>
> The upper dir inode_lock is taken instead of rename_lock,
> because it is needed for lookup and later for linking the
> temp file, but it is released while copying up data.
>
> Suggested-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/overlayfs/copy_up.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index d3b6c15..ddf5e2d 100644
> --- a/fs/overlayfs/copy_up.c
> +++ b/fs/overlayfs/copy_up.c
> @@ -291,7 +291,14 @@ 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);
> +
> + if (tmpfile)
> + inode_lock_nested(udir, I_MUTEX_PARENT);
> +
> if (err)
> goto out_cleanup;
> }
> @@ -371,6 +378,19 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
> return PTR_ERR(link);
> }
>
> + if (tmpfile) {
> + err = ovl_copy_up_start(dentry);
> + /* err < 0: interrupted, err > 0: raced with another copy-up */
> + if (unlikely(err)) {
> + pr_debug("ovl_copy_up_start(%pd2) = %i\n", dentry, err);
> + if (err > 0)
> + err = 0;
> + goto out_done;
> + }
> + /* lock_rename/unlock_rename will lock/unlock only upperdir */
> + workdir = upperdir;
Unnecessary obfuscation. Just do lock_inode(); ovl_copy_up_locked();
unlokc_inode();.
Thanks,
Miklos
> + }
> +
> err = -EIO;
> if (lock_rename(workdir, upperdir) != NULL) {
> pr_err("overlayfs: failed to lock workdir+upperdir\n");
> @@ -390,6 +410,9 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
> }
> out_unlock:
> unlock_rename(workdir, upperdir);
> + if (tmpfile)
> + ovl_copy_up_end(dentry);
> +out_done:
> do_delayed_call(&done);
>
> return err;
> --
> 2.7.4
>
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