Stop pinning modules indefinitely upon FLB registration.
Instead, dynamically take a module reference when the FLB is actively
used in a session (e.g., during preserve and retrieve) and release it
when the session concludes.
This allows modules providing FLB operations to be cleanly unloaded
when not in active use by the live update orchestrator.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
kernel/liveupdate/luo_flb.c | 27 +++++++++++++++++----------
1 file changed, 17 insertions(+), 10 deletions(-)
diff --git a/kernel/liveupdate/luo_flb.c b/kernel/liveupdate/luo_flb.c
index 3c91d0008eb1..ce28ce9b113e 100644
--- a/kernel/liveupdate/luo_flb.c
+++ b/kernel/liveupdate/luo_flb.c
@@ -115,10 +115,15 @@ static int luo_flb_file_preserve_one(struct liveupdate_flb *flb)
struct liveupdate_flb_op_args args = {0};
int err;
+ if (!try_module_get(flb->ops->owner))
+ return -ENODEV;
+
args.flb = flb;
err = flb->ops->preserve(&args);
- if (err)
+ if (err) {
+ module_put(flb->ops->owner);
return err;
+ }
private->outgoing.data = args.data;
private->outgoing.obj = args.obj;
}
@@ -146,6 +151,7 @@ static void luo_flb_file_unpreserve_one(struct liveupdate_flb *flb)
private->outgoing.data = 0;
private->outgoing.obj = NULL;
+ module_put(flb->ops->owner);
}
}
}
@@ -181,12 +187,17 @@ static int luo_flb_retrieve_one(struct liveupdate_flb *flb)
if (!found)
return -ENOENT;
+ if (!try_module_get(flb->ops->owner))
+ return -ENODEV;
+
args.flb = flb;
args.data = private->incoming.data;
err = flb->ops->retrieve(&args);
- if (err)
+ if (err) {
+ module_put(flb->ops->owner);
return err;
+ }
private->incoming.obj = args.obj;
private->incoming.retrieved = true;
@@ -237,6 +248,7 @@ static void luo_flb_file_finish_one(struct liveupdate_flb *flb)
private->incoming.data = 0;
private->incoming.obj = NULL;
private->incoming.finished = true;
+ module_put(flb->ops->owner);
}
}
}
@@ -412,11 +424,6 @@ int liveupdate_register_flb(struct liveupdate_file_handler *fh,
goto err_resume;
}
- if (!try_module_get(flb->ops->owner)) {
- err = -EAGAIN;
- goto err_resume;
- }
-
list_add_tail(&private->list, &luo_flb_global.list);
luo_flb_global.count++;
}
@@ -493,12 +500,11 @@ int liveupdate_unregister_flb(struct liveupdate_file_handler *fh,
private->users--;
/*
* If this is the last file-handler with which we are registred, remove
- * from the global list, and relese module reference.
+ * from the global list.
*/
if (!private->users) {
list_del_init(&private->list);
luo_flb_global.count--;
- module_put(flb->ops->owner);
}
up_write(&luo_register_rwlock);
@@ -527,7 +533,8 @@ int liveupdate_unregister_flb(struct liveupdate_file_handler *fh,
*
* Return: 0 on success, or a negative errno on failure. -ENODATA means no
* incoming FLB data, -ENOENT means specific flb not found in the incoming
- * data, and -EOPNOTSUPP when live update is disabled or not configured.
+ * data, -ENODEV if the FLB's module is unloading, and -EOPNOTSUPP when
+ * live update is disabled or not configured.
*/
int liveupdate_flb_get_incoming(struct liveupdate_flb *flb, void **objp)
{
--
2.43.0On Fri, Mar 27 2026, Pasha Tatashin wrote: > Stop pinning modules indefinitely upon FLB registration. > Instead, dynamically take a module reference when the FLB is actively > used in a session (e.g., during preserve and retrieve) and release it > when the session concludes. > > This allows modules providing FLB operations to be cleanly unloaded > when not in active use by the live update orchestrator. > > Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com> This is good for now but I think we should rework the FLB registration down the line. File handlers should not use the FLB before registering first, and we should initialize the FLB on registration. At this point, if there is incoming data for the FLB the module reference should be taken since now there are files depending on that module. Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org> [...] -- Regards, Pratyush Yadav
On Fri, Mar 27, 2026 at 03:33:29AM +0000, Pasha Tatashin wrote:
>Stop pinning modules indefinitely upon FLB registration.
>Instead, dynamically take a module reference when the FLB is actively
>used in a session (e.g., during preserve and retrieve) and release it
>when the session concludes.
>
>This allows modules providing FLB operations to be cleanly unloaded
>when not in active use by the live update orchestrator.
>
>Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
>---
> kernel/liveupdate/luo_flb.c | 27 +++++++++++++++++----------
> 1 file changed, 17 insertions(+), 10 deletions(-)
>
>diff --git a/kernel/liveupdate/luo_flb.c b/kernel/liveupdate/luo_flb.c
>index 3c91d0008eb1..ce28ce9b113e 100644
>--- a/kernel/liveupdate/luo_flb.c
>+++ b/kernel/liveupdate/luo_flb.c
>@@ -115,10 +115,15 @@ static int luo_flb_file_preserve_one(struct liveupdate_flb *flb)
> struct liveupdate_flb_op_args args = {0};
> int err;
>
>+ if (!try_module_get(flb->ops->owner))
>+ return -ENODEV;
>+
> args.flb = flb;
> err = flb->ops->preserve(&args);
>- if (err)
>+ if (err) {
>+ module_put(flb->ops->owner);
> return err;
>+ }
> private->outgoing.data = args.data;
> private->outgoing.obj = args.obj;
> }
>@@ -146,6 +151,7 @@ static void luo_flb_file_unpreserve_one(struct liveupdate_flb *flb)
>
> private->outgoing.data = 0;
> private->outgoing.obj = NULL;
>+ module_put(flb->ops->owner);
> }
> }
> }
>@@ -181,12 +187,17 @@ static int luo_flb_retrieve_one(struct liveupdate_flb *flb)
> if (!found)
> return -ENOENT;
>
>+ if (!try_module_get(flb->ops->owner))
>+ return -ENODEV;
>+
> args.flb = flb;
> args.data = private->incoming.data;
>
> err = flb->ops->retrieve(&args);
>- if (err)
>+ if (err) {
>+ module_put(flb->ops->owner);
> return err;
>+ }
>
> private->incoming.obj = args.obj;
> private->incoming.retrieved = true;
>@@ -237,6 +248,7 @@ static void luo_flb_file_finish_one(struct liveupdate_flb *flb)
> private->incoming.data = 0;
> private->incoming.obj = NULL;
> private->incoming.finished = true;
>+ module_put(flb->ops->owner);
> }
> }
> }
>@@ -412,11 +424,6 @@ int liveupdate_register_flb(struct liveupdate_file_handler *fh,
> goto err_resume;
> }
>
>- if (!try_module_get(flb->ops->owner)) {
>- err = -EAGAIN;
>- goto err_resume;
>- }
>-
> list_add_tail(&private->list, &luo_flb_global.list);
> luo_flb_global.count++;
> }
>@@ -493,12 +500,11 @@ int liveupdate_unregister_flb(struct liveupdate_file_handler *fh,
> private->users--;
> /*
> * If this is the last file-handler with which we are registred, remove
>- * from the global list, and relese module reference.
>+ * from the global list.
> */
> if (!private->users) {
> list_del_init(&private->list);
> luo_flb_global.count--;
>- module_put(flb->ops->owner);
> }
>
> up_write(&luo_register_rwlock);
>@@ -527,7 +533,8 @@ int liveupdate_unregister_flb(struct liveupdate_file_handler *fh,
> *
> * Return: 0 on success, or a negative errno on failure. -ENODATA means no
> * incoming FLB data, -ENOENT means specific flb not found in the incoming
>- * data, and -EOPNOTSUPP when live update is disabled or not configured.
>+ * data, -ENODEV if the FLB's module is unloading, and -EOPNOTSUPP when
>+ * live update is disabled or not configured.
> */
> int liveupdate_flb_get_incoming(struct liveupdate_flb *flb, void **objp)
> {
>--
>2.43.0
>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
On Mon, Mar 30, 2026 at 12:56 PM Samiullah Khawaja <skhawaja@google.com> wrote:
>
> On Fri, Mar 27, 2026 at 03:33:29AM +0000, Pasha Tatashin wrote:
> >Stop pinning modules indefinitely upon FLB registration.
> >Instead, dynamically take a module reference when the FLB is actively
> >used in a session (e.g., during preserve and retrieve) and release it
> >when the session concludes.
> >
> >This allows modules providing FLB operations to be cleanly unloaded
> >when not in active use by the live update orchestrator.
> >
> >Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> >---
> > kernel/liveupdate/luo_flb.c | 27 +++++++++++++++++----------
> > 1 file changed, 17 insertions(+), 10 deletions(-)
> >
> >diff --git a/kernel/liveupdate/luo_flb.c b/kernel/liveupdate/luo_flb.c
> >index 3c91d0008eb1..ce28ce9b113e 100644
> >--- a/kernel/liveupdate/luo_flb.c
> >+++ b/kernel/liveupdate/luo_flb.c
> >@@ -115,10 +115,15 @@ static int luo_flb_file_preserve_one(struct liveupdate_flb *flb)
> > struct liveupdate_flb_op_args args = {0};
> > int err;
> >
> >+ if (!try_module_get(flb->ops->owner))
> >+ return -ENODEV;
> >+
> > args.flb = flb;
> > err = flb->ops->preserve(&args);
> >- if (err)
> >+ if (err) {
> >+ module_put(flb->ops->owner);
> > return err;
> >+ }
> > private->outgoing.data = args.data;
> > private->outgoing.obj = args.obj;
> > }
> >@@ -146,6 +151,7 @@ static void luo_flb_file_unpreserve_one(struct liveupdate_flb *flb)
> >
> > private->outgoing.data = 0;
> > private->outgoing.obj = NULL;
> >+ module_put(flb->ops->owner);
> > }
> > }
> > }
> >@@ -181,12 +187,17 @@ static int luo_flb_retrieve_one(struct liveupdate_flb *flb)
> > if (!found)
> > return -ENOENT;
> >
> >+ if (!try_module_get(flb->ops->owner))
> >+ return -ENODEV;
> >+
> > args.flb = flb;
> > args.data = private->incoming.data;
> >
> > err = flb->ops->retrieve(&args);
> >- if (err)
> >+ if (err) {
> >+ module_put(flb->ops->owner);
> > return err;
> >+ }
> >
> > private->incoming.obj = args.obj;
> > private->incoming.retrieved = true;
> >@@ -237,6 +248,7 @@ static void luo_flb_file_finish_one(struct liveupdate_flb *flb)
> > private->incoming.data = 0;
> > private->incoming.obj = NULL;
> > private->incoming.finished = true;
> >+ module_put(flb->ops->owner);
> > }
> > }
> > }
> >@@ -412,11 +424,6 @@ int liveupdate_register_flb(struct liveupdate_file_handler *fh,
> > goto err_resume;
> > }
> >
> >- if (!try_module_get(flb->ops->owner)) {
> >- err = -EAGAIN;
> >- goto err_resume;
> >- }
> >-
> > list_add_tail(&private->list, &luo_flb_global.list);
> > luo_flb_global.count++;
> > }
> >@@ -493,12 +500,11 @@ int liveupdate_unregister_flb(struct liveupdate_file_handler *fh,
> > private->users--;
> > /*
> > * If this is the last file-handler with which we are registred, remove
> >- * from the global list, and relese module reference.
> >+ * from the global list.
> > */
> > if (!private->users) {
> > list_del_init(&private->list);
> > luo_flb_global.count--;
> >- module_put(flb->ops->owner);
> > }
> >
> > up_write(&luo_register_rwlock);
> >@@ -527,7 +533,8 @@ int liveupdate_unregister_flb(struct liveupdate_file_handler *fh,
> > *
> > * Return: 0 on success, or a negative errno on failure. -ENODATA means no
> > * incoming FLB data, -ENOENT means specific flb not found in the incoming
> >- * data, and -EOPNOTSUPP when live update is disabled or not configured.
> >+ * data, -ENODEV if the FLB's module is unloading, and -EOPNOTSUPP when
> >+ * live update is disabled or not configured.
> > */
> > int liveupdate_flb_get_incoming(struct liveupdate_flb *flb, void **objp)
> > {
> >--
> >2.43.0
> >
>
> Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Thank you Sami.
Pasha
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