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liveupdate: defer file handler module refcounting to active sessions 

Stop pinning modules indefinitely upon file handler registration. 
Instead, dynamically increment the module reference count only when a live
update session actively uses the file handler (e.g., during preservation
or deserialization), and release it when the session ends.

This allows modules providing live update handlers to be gracefully
unloaded when no live update is in progress.

Link: https://lore.kernel.org/20260327033335.696621-11-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
master
Pasha Tatashin 2026-03-27 03:33:34 +00:00 committed by Andrew Morton
parent 2ab7207e7e
commit 68750e820b
1 changed files with 12 additions and 12 deletions
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24
kernel/liveupdate/luo_file.c
View File

@ -291,7 +291,8 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)
down_read(&luo_register_rwlock);
list_private_for_each_entry(fh, &luo_file_handler_list, list) {
if (fh->ops->can_preserve(fh, file)) {
err = 0;
if (try_module_get(fh->ops->owner))
err = 0;
break;
}
}
@ -304,7 +305,7 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)
err = xa_insert(&luo_preserved_files, luo_get_id(fh, file),
file, GFP_KERNEL);
if (err)
goto err_free_files_mem;
goto err_module_put;
err = luo_flb_file_preserve(fh);
if (err)
@ -340,6 +341,8 @@ err_flb_unpreserve:
luo_flb_file_unpreserve(fh);
err_erase_xa:
xa_erase(&luo_preserved_files, luo_get_id(fh, file));
err_module_put:
module_put(fh->ops->owner);
err_free_files_mem:
luo_free_files_mem(file_set);
err_fput:
@ -382,6 +385,7 @@ void luo_file_unpreserve_files(struct luo_file_set *file_set)
args.private_data = luo_file->private_data;
luo_file->fh->ops->unpreserve(&args);
luo_flb_file_unpreserve(luo_file->fh);
module_put(luo_file->fh->ops->owner);
xa_erase(&luo_preserved_files,
luo_get_id(luo_file->fh, luo_file->file));
@ -673,6 +677,7 @@ static void luo_file_finish_one(struct luo_file_set *file_set,
luo_file->fh->ops->finish(&args);
luo_flb_file_finish(luo_file->fh);
module_put(luo_file->fh->ops->owner);
}
/**
@ -810,7 +815,8 @@ int luo_file_deserialize(struct luo_file_set *file_set,
down_read(&luo_register_rwlock);
list_private_for_each_entry(fh, &luo_file_handler_list, list) {
if (!strcmp(fh->compatible, file_ser[i].compatible)) {
handler_found = true;
if (try_module_get(fh->ops->owner))
handler_found = true;
break;
}
}
@ -824,8 +830,10 @@ int luo_file_deserialize(struct luo_file_set *file_set,
}
luo_file = kzalloc_obj(*luo_file);
if (!luo_file)
if (!luo_file) {
module_put(fh->ops->owner);
return -ENOMEM;
}
luo_file->fh = fh;
luo_file->file = NULL;
@ -886,12 +894,6 @@ int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)
}
}
/* Pin the module implementing the handler */
if (!try_module_get(fh->ops->owner)) {
err = -EAGAIN;
goto err_unlock;
}
INIT_LIST_HEAD(&ACCESS_PRIVATE(fh, flb_list));
INIT_LIST_HEAD(&ACCESS_PRIVATE(fh, list));
list_add_tail(&ACCESS_PRIVATE(fh, list), &luo_file_handler_list);
@ -921,6 +923,4 @@ void liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh)
guard(rwsem_write)(&luo_register_rwlock);
luo_flb_unregister_all(fh);
list_del(&ACCESS_PRIVATE(fh, list));
module_put(fh->ops->owner);
}