From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2788D175A9E for ; Fri, 27 Mar 2026 17:22:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774632177; cv=none; b=Bb0xVJOVx3WDGIz7CUw2RwcYAOSaunvchDNXxx+Mw8cOxXO8Fl4qeKWkn5PKHmFLAFwNA8QkK9XrVZs/WniOduHrJ+9U2vDdZC/FiDYPMBQPnIcOVmXspfPjM0mD5YKt+PYkGVKNSwmDrDh1JgANgXRrJE/dEI8DdPPNYPD32vI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774632177; c=relaxed/simple; bh=jA0dITAyYIADKCkTQOFLEYdpvXs7p4ZOvI0gC+GMcSw=; h=Date:To:From:Subject:Message-Id; b=YQ+mX3uMWwy4QbxDy+68Glzt3ughffIIKGxjLuHuFQQ+qW5Q3Yc4IdULgT63GV70hMvJ3866GX6tgY5DBkVrUCQYjvmgewE6hh6A05qO5C5VQ+FVfKTdXmUjsF4UONU3k1/8r3rdEH1O9jMG1zKyLvdSmC891Pe0Y0NlNs15Mw4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=H0bUA7H6; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="H0bUA7H6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C0254C19423; Fri, 27 Mar 2026 17:22:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1774632176; bh=jA0dITAyYIADKCkTQOFLEYdpvXs7p4ZOvI0gC+GMcSw=; h=Date:To:From:Subject:From; b=H0bUA7H6Lvrn9HwJVXymVPg+Z+X9ekPDYRvbnsopBpvMzQHapD9X8mXJ1ZEAdPtIN 63XIuVvOikQvmG7ZN4xCPnrJkhT0GtuEmx8oqUMvovpZhwmFHyC/M3nYED0c0jDHbZ QylUhovtzpanItefe2eJgnb8ipuE7+AAL1RdA2pU= Date: Fri, 27 Mar 2026 10:22:56 -0700 To: mm-commits@vger.kernel.org,pasha.tatashin@soleen.com,akpm@linux-foundation.org From: Andrew Morton Subject: + liveupdate-defer-file-handler-module-refcounting-to-active-sessions.patch added to mm-new branch Message-Id: <20260327172256.C0254C19423@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: liveupdate: defer file handler module refcounting to active sessions has been added to the -mm mm-new branch. Its filename is liveupdate-defer-file-handler-module-refcounting-to-active-sessions.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/liveupdate-defer-file-handler-module-refcounting-to-active-sessions.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next If a few days of testing in mm-new is successful, the patch will me moved into mm.git's mm-unstable branch, which is included in linux-next Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Pasha Tatashin Subject: liveupdate: defer file handler module refcounting to active sessions Date: Fri, 27 Mar 2026 03:33:34 +0000 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://lkml.kernel.org/r/20260327033335.696621-11-pasha.tatashin@soleen.com Signed-off-by: Pasha Tatashin Cc: David Matlack Cc: Mike Rapoport Cc: Pratyush Yadav Cc: Samiullah Khawaja Signed-off-by: Andrew Morton --- kernel/liveupdate/luo_file.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) --- a/kernel/liveupdate/luo_file.c~liveupdate-defer-file-handler-module-refcounting-to-active-sessions +++ a/kernel/liveupdate/luo_file.c @@ -291,7 +291,8 @@ int luo_preserve_file(struct luo_file_se 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_se 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 lu 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 l 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 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 } 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(str } } - /* 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( guard(rwsem_write)(&luo_register_rwlock); luo_flb_unregister_all(fh); list_del(&ACCESS_PRIVATE(fh, list)); - - module_put(fh->ops->owner); } _ Patches currently in -mm which might be from pasha.tatashin@soleen.com are liveupdate-prevent-double-management-of-files.patch memfd-implement-get_id-for-memfd_luo.patch selftests-liveupdate-add-test-for-double-preservation.patch liveupdate-safely-print-untrusted-strings.patch liveupdate-synchronize-lazy-initialization-of-flb-private-state.patch liveupdate-protect-file-handler-list-with-rwsem.patch liveupdate-protect-flb-lists-with-luo_register_rwlock.patch liveupdate-defer-flb-module-refcounting-to-active-sessions.patch liveupdate-remove-luo_session_quiesce.patch liveupdate-auto-unregister-flbs-on-file-handler-unregistration.patch liveupdate-remove-liveupdate_test_unregister.patch liveupdate-make-unregister-functions-return-void.patch liveupdate-defer-file-handler-module-refcounting-to-active-sessions.patch