linux-kernel - [PATCH RFC v2 1/5] nvme: add __always_inline for nvme_pci_npages

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Message-Id: <20250416-noautoinline-v2-1-e69a2717530f@uniontech.com>
Date: Wed, 16 Apr 2025 17:44:47 +0800
From: Chen Linxuan via B4 Relay <devnull+chenlinxuan.uniontech.com@...nel.org>
To: Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...nel.dk>, 
 Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>, 
 Andrew Morton <akpm@...ux-foundation.org>, 
 Yishai Hadas <yishaih@...dia.com>, Jason Gunthorpe <jgg@...pe.ca>, 
 Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>, 
 Kevin Tian <kevin.tian@...el.com>, 
 Alex Williamson <alex.williamson@...hat.com>, 
 Peter Huewe <peterhuewe@....de>, Jarkko Sakkinen <jarkko@...nel.org>, 
 Masahiro Yamada <masahiroy@...nel.org>, 
 Nathan Chancellor <nathan@...nel.org>, 
 Nicolas Schier <nicolas.schier@...ux.dev>, 
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>, 
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>
Cc: linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 linux-mm@...ck.org, kvm@...r.kernel.org, virtualization@...ts.linux.dev, 
 linux-integrity@...r.kernel.org, linux-kbuild@...r.kernel.org, 
 llvm@...ts.linux.dev, Winston Wen <wentao@...ontech.com>, 
 Chen Linxuan <chenlinxuan@...ontech.com>, 
 Changbin Du <changbin.du@...el.com>
Subject: [PATCH RFC v2 1/5] nvme: add __always_inline for
 nvme_pci_npages_prp

From: Winston Wen <wentao@...ontech.com>

On x86_64 with gcc version 13.3.0, I build drivers/nvme/host/pci.c
with:

  make defconfig
  ./scripts/kconfig/merge_config.sh .config <(
    echo CONFIG_BLK_DEV_NVME=m
  )
  make KCFLAGS="-fno-inline-small-functions -fno-inline-functions-called-once" \
    drivers/nvme/host/pci.o

Then I get a compile error:

    CALL    scripts/checksyscalls.sh
    DESCEND objtool
    INSTALL libsubcmd_headers
    CC      drivers/nvme/host/pci.o
  In file included from <command-line>:
  drivers/nvme/host/pci.c: In function 'nvme_init':
  ././include/linux/compiler_types.h:557:45: error: call to '__compiletime_assert_878' declared with attribute error: BUILD_BUG_ON failed: nvme_pci_npages_prp() > NVME_MAX_NR_ALLOCATIONS
    557 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
        |                                             ^
  ././include/linux/compiler_types.h:538:25: note: in definition of macro '__compiletime_assert'
    538 |                         prefix ## suffix();                             \
        |                         ^~~~~~
  ././include/linux/compiler_types.h:557:9: note: in expansion of macro '_compiletime_assert'
    557 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
        |         ^~~~~~~~~~~~~~~~~~~
  ./include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
     39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
        |                                     ^~~~~~~~~~~~~~~~~~
  ./include/linux/build_bug.h:50:9: note: in expansion of macro 'BUILD_BUG_ON_MSG'
     50 |         BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
        |         ^~~~~~~~~~~~~~~~
  drivers/nvme/host/pci.c:3804:9: note: in expansion of macro 'BUILD_BUG_ON'
   3804 |         BUILD_BUG_ON(nvme_pci_npages_prp() > NVME_MAX_NR_ALLOCATIONS);
        |         ^~~~~~~~~~~~

Mark nvme_pci_npages_prp() with __always_inline make it can be computed
at compile time.

Co-developed-by: Chen Linxuan <chenlinxuan@...ontech.com>
Signed-off-by: Chen Linxuan <chenlinxuan@...ontech.com>
Signed-off-by: Winston Wen <wentao@...ontech.com>
---
 drivers/nvme/host/pci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index b178d52eac1b7f7286e217226b9b3686d07b7b6c..9ab070a9f0372bc6595c29a884ee9f2ffe5ae8e9 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -390,7 +390,7 @@ static bool nvme_dbbuf_update_and_check_event(u16 value, __le32 *dbbuf_db,
  * as it only leads to a small amount of wasted memory for the lifetime of
  * the I/O.
  */
-static int nvme_pci_npages_prp(void)
+static __always_inline int nvme_pci_npages_prp(void)
 {
 	unsigned max_bytes = (NVME_MAX_KB_SZ * 1024) + NVME_CTRL_PAGE_SIZE;
 	unsigned nprps = DIV_ROUND_UP(max_bytes, NVME_CTRL_PAGE_SIZE);

-- 
2.48.1