On Mon, Jan 16, 2017 at 12:58 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 | 46 ++++++++++++++++++++++++++++++++++++----------
> 1 file changed, 36 insertions(+), 10 deletions(-)
>
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index d3b6c15..0d1cb96 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;
> }
> @@ -371,15 +378,28 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
> return PTR_ERR(link);
> }
>
> - err = -EIO;
> - if (lock_rename(workdir, upperdir) != NULL) {
> - pr_err("overlayfs: failed to lock workdir+upperdir\n");
> - goto out_unlock;
> - }
> - if (ovl_dentry_upper(dentry)) {
> - /* Raced with another copy-up? Nothing to do, then... */
> - err = 0;
> - goto out_unlock;
> + 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 upper dir for lookup, link tmpfile, set_timestamps */
> + inode_lock_nested(upperdir->d_inode, I_MUTEX_PARENT);
> + } else {
> + err = -EIO;
> + if (lock_rename(workdir, upperdir) != NULL) {
> + pr_err("overlayfs: failed to lock workdir+upperdir\n");
> + goto out_unlock;
> + }
> + if (ovl_dentry_upper(dentry)) {
> + /* Raced with another copy-up? Nothing to do */
> + err = 0;
> + goto out_unlock;
> + }
> }
>
> err = ovl_copy_up_locked(workdir, upperdir, dentry, lowerpath,
> @@ -389,7 +409,13 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
> ovl_set_timestamps(upperdir, &pstat);
Or move ovl_set_timestamps() into ovl_copy_up_locked().
Lock and unlock in a different block will be confusing at best.
Thanks,
Miklos
> }
> out_unlock:
> - unlock_rename(workdir, upperdir);
> + if (tmpfile)
> + inode_unlock(upperdir->d_inode);
> + else
> + 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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