[PATCH v2 17/20] ovl: generalize ovl_copy_up_one() using actors

Amir Goldstein
2017-06-07T07:51:45Z

ovl_copy_up_one() is implementing two different locking methods
for regular files and non-regular files.

Implement the actors aquire,release for the 'workdir' and 'tmpfile'
copy up methods and use them to generalize locking in ovl_copy_up_one().

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/overlayfs/copy_up.c | 59 ++++++++++++++++++++++++++++----------------------
1 file changed, 33 insertions(+), 26 deletions(-)

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index b01be9517de9..843ba9ca7bfc 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -381,7 +381,23 @@ struct ovl_copy_up_ops {
*/
static int ovl_copy_up_workdir_aquire(struct ovl_copy_up_ctx *ctx)
{
+ int err = -EIO;
+
+ if (lock_rename(ctx->tempdir, ctx->upperdir) != NULL) {
+ pr_err("overlayfs: failed to lock workdir+upperdir\n");
+ goto out_unlock;
+ }
+ if (ovl_dentry_upper(ctx->dentry)) {
+ /* Raced with another copy-up? */
+ err = 1;
+ goto out_unlock;
+ }
+
return 0;
+
+out_unlock:
+ unlock_rename(ctx->tempdir, ctx->upperdir);
+ return err;
}

static int ovl_copy_up_workdir_prepare(struct ovl_copy_up_ctx *ctx)
@@ -451,6 +467,7 @@ static int ovl_copy_up_workdir_cancel(struct ovl_copy_up_ctx *ctx)

static int ovl_copy_up_workdir_release(struct ovl_copy_up_ctx *ctx)
{
+ unlock_rename(ctx->tempdir, ctx->upperdir);
return 0;
}

@@ -468,7 +485,7 @@ static const struct ovl_copy_up_ops ovl_copy_up_workdir_ops = {
*/
static int ovl_copy_up_tmpfile_aquire(struct ovl_copy_up_ctx *ctx)
{
- return 0;
+ return ovl_copy_up_start(ctx->dentry);
}

static int ovl_copy_up_tmpfile_prepare(struct ovl_copy_up_ctx *ctx)
@@ -514,6 +531,7 @@ static int ovl_copy_up_tmpfile_cancel(struct ovl_copy_up_ctx *ctx)

static int ovl_copy_up_tmpfile_release(struct ovl_copy_up_ctx *ctx)
{
+ ovl_copy_up_end(ctx->dentry);
return 0;
}

@@ -599,6 +617,7 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
.link = NULL,
.tempdir = ovl_workdir(dentry),
};
+ const struct ovl_copy_up_ops *ops;

if (WARN_ON(!ctx.tempdir))
return -EROFS;
@@ -625,35 +644,23 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
}

/* Should we copyup with O_TMPFILE or with workdir? */
- if (S_ISREG(stat->mode) && ofs->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;
- }
-
- err = ovl_copy_up_locked(&ctx, &ovl_copy_up_tmpfile_ops);
- ovl_copy_up_end(dentry);
+ if (S_ISREG(stat->mode) && ofs->tmpfile)
+ ops = &ovl_copy_up_tmpfile_ops;
+ else
+ ops = &ovl_copy_up_workdir_ops;
+
+ err = ops->aquire(&ctx);
+ /* err < 0: interrupted, err > 0: raced with another copy-up */
+ if (unlikely(err)) {
+ pr_debug("%s(%pd2): aquire = %i\n", __func__, dentry, err);
+ if (err > 0)
+ err = 0;
goto out_done;
}

- err = -EIO;
- if (lock_rename(ctx.tempdir, ctx.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;
- }
+ err = ovl_copy_up_locked(&ctx, ops);
+ ops->release(&ctx);

- err = ovl_copy_up_locked(&ctx, &ovl_copy_up_workdir_ops);
-out_unlock:
- unlock_rename(ctx.tempdir, ctx.upperdir);
out_done:
do_delayed_call(&done);

--
2.7.4