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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Coly Li <colyli@suse.de>, Jens Axboe <axboe@kernel.dk>,
	Sasha Levin <sashal@kernel.org>,
	linux-bcache@vger.kernel.org
Subject: [PATCH AUTOSEL 4.9 031/114] bcache: avoid clang -Wunintialized warning
Date: Wed, 22 May 2019 15:28:54 -0400	[thread overview]
Message-ID: <20190522193017.26567-31-sashal@kernel.org> (raw)
In-Reply-To: <20190522193017.26567-1-sashal@kernel.org>

From: Arnd Bergmann <arnd@arndb.de>

[ Upstream commit 78d4eb8ad9e1d413449d1b7a060f50b6efa81ebd ]

clang has identified a code path in which it thinks a
variable may be unused:

drivers/md/bcache/alloc.c:333:4: error: variable 'bucket' is used uninitialized whenever 'if' condition is false
      [-Werror,-Wsometimes-uninitialized]
                        fifo_pop(&ca->free_inc, bucket);
                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/md/bcache/util.h:219:27: note: expanded from macro 'fifo_pop'
 #define fifo_pop(fifo, i)       fifo_pop_front(fifo, (i))
                                ^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/md/bcache/util.h:189:6: note: expanded from macro 'fifo_pop_front'
        if (_r) {                                                       \
            ^~
drivers/md/bcache/alloc.c:343:46: note: uninitialized use occurs here
                        allocator_wait(ca, bch_allocator_push(ca, bucket));
                                                                  ^~~~~~
drivers/md/bcache/alloc.c:287:7: note: expanded from macro 'allocator_wait'
                if (cond)                                               \
                    ^~~~
drivers/md/bcache/alloc.c:333:4: note: remove the 'if' if its condition is always true
                        fifo_pop(&ca->free_inc, bucket);
                        ^
drivers/md/bcache/util.h:219:27: note: expanded from macro 'fifo_pop'
 #define fifo_pop(fifo, i)       fifo_pop_front(fifo, (i))
                                ^
drivers/md/bcache/util.h:189:2: note: expanded from macro 'fifo_pop_front'
        if (_r) {                                                       \
        ^
drivers/md/bcache/alloc.c:331:15: note: initialize the variable 'bucket' to silence this warning
                        long bucket;
                                   ^

This cannot happen in practice because we only enter the loop
if there is at least one element in the list.

Slightly rearranging the code makes this clearer to both the
reader and the compiler, which avoids the warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/md/bcache/alloc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index dd344ee9e62b7..ebacd21714efa 100644
--- a/drivers/md/bcache/alloc.c
+++ b/drivers/md/bcache/alloc.c
@@ -322,10 +322,11 @@ static int bch_allocator_thread(void *arg)
 		 * possibly issue discards to them, then we add the bucket to
 		 * the free list:
 		 */
-		while (!fifo_empty(&ca->free_inc)) {
+		while (1) {
 			long bucket;
 
-			fifo_pop(&ca->free_inc, bucket);
+			if (!fifo_pop(&ca->free_inc, bucket))
+				break;
 
 			if (ca->discard) {
 				mutex_unlock(&ca->set->bucket_lock);
-- 
2.20.1


  parent reply	other threads:[~2019-05-22 19:34 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-22 19:28 [PATCH AUTOSEL 4.9 001/114] gfs2: Fix lru_count going negative Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 002/114] cxgb4: Fix error path in cxgb4_init_module Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 003/114] mmc: core: Verify SD bus width Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 004/114] dmaengine: tegra210-dma: free dma controller in remove() Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 005/114] net: ena: gcc 8: fix compilation warning Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 006/114] orangefs: truncate before updating size Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 007/114] ASoC: hdmi-codec: unlock the device on startup errors Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 008/114] powerpc/boot: Fix missing check of lseek() return value Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 009/114] ASoC: imx: fix fiq dependencies Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 010/114] spi: pxa2xx: fix SCR (divisor) calculation Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 011/114] brcm80211: potential NULL dereference in brcmf_cfg80211_vndr_cmds_dcmd_handler() Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 012/114] ARM: vdso: Remove dependency with the arch_timer driver internals Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 013/114] arm64: Fix compiler warning from pte_unmap() with -Wunused-but-set-variable Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 014/114] sched/cpufreq: Fix kobject memleak Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 015/114] scsi: qla2xxx: Fix a qla24xx_enable_msix() error path Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 016/114] iwlwifi: pcie: don't crash on invalid RX interrupt Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 017/114] rtc: 88pm860x: prevent use-after-free on device remove Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 018/114] w1: fix the resume command API Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 019/114] dmaengine: pl330: _stop: clear interrupt status Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 020/114] mac80211/cfg80211: update bss channel on channel switch Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 021/114] driver core: platform: Fix the usage of platform device name(pdev->name) Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 022/114] ASoC: fsl_sai: Update is_slave_mode with correct value Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 023/114] mwifiex: prevent an array overflow Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 024/114] net: cw1200: fix a NULL pointer dereference Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 025/114] at76c50x-usb: Don't register led_trigger if usb_register_driver failed Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 026/114] ssb: Fix possible NULL pointer dereference in ssb_host_pcmcia_exit Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 027/114] crypto: sun4i-ss - Fix invalid calculation of hash end Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 028/114] bcache: return error immediately in bch_journal_replay() Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 029/114] bcache: fix failure in journal relplay Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 030/114] bcache: add failure check to run_cache_set() for journal replay Sasha Levin
2019-05-22 19:28 ` Sasha Levin [this message]
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 032/114] RDMA/cma: Consider scope_id while binding to ipv6 ll address Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 033/114] x86/build: Move _etext to actual end of .text Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 034/114] smpboot: Place the __percpu annotation correctly Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 035/114] x86/mm: Remove in_nmi() warning from 64-bit implementation of vmalloc_fault() Sasha Levin
2019-05-22 19:28 ` [PATCH AUTOSEL 4.9 036/114] mm/uaccess: Use 'unsigned long' to placate UBSAN warnings on older GCC versions Sasha Levin
2019-05-22 19:29 ` [PATCH AUTOSEL 4.9 037/114] HID: logitech-hidpp: use RAP instead of FAP to get the protocol version Sasha Levin
2019-05-22 19:29 ` [PATCH AUTOSEL 4.9 038/114] pinctrl: pistachio: fix leaked of_node references Sasha Levin
2019-05-22 19:29 ` [PATCH AUTOSEL 4.9 039/114] dmaengine: at_xdmac: remove BUG_ON macro in tasklet Sasha Levin
2019-05-22 19:29 ` [PATCH AUTOSEL 4.9 040/114] media: coda: clear error return value before picture run Sasha Levin
2019-05-22 19:29 ` [PATCH AUTOSEL 4.9 041/114] media: ov6650: Move v4l2_clk_get() to ov6650_video_probe() helper Sasha Levin
2019-05-22 19:29 ` [PATCH AUTOSEL 4.9 042/114] media: au0828: stop video streaming only when last user stops Sasha Levin

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