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| author | Anders Roxell <anders.roxell@linaro.org> | 2018-10-30 14:35:45 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-01-26 11:37:01 +0300 |
| commit | b7bf54a9cd61766bfc54d5c22d191ff2160f5ea9 (patch) | |
| tree | 28ab0cd9bd4fb262a50addabc12d1b4a94e4a611 | |
| parent | 18947188046cf1dbe85d4e4f27edb55a025b8a92 (diff) | |
| download | linux-b7bf54a9cd61766bfc54d5c22d191ff2160f5ea9.tar.xz | |
writeback: don't decrement wb->refcnt if !wb->bdi
[ Upstream commit 347a28b586802d09604a149c1a1f6de5dccbe6fa ]
This happened while running in qemu-system-aarch64, the AMBA PL011 UART
driver when enabling CONFIG_DEBUG_TEST_DRIVER_REMOVE.
arch_initcall(pl011_init) came before subsys_initcall(default_bdi_init),
devtmpfs' handle_remove() crashes because the reference count is a NULL
pointer only because wb->bdi hasn't been initialized yet.
Rework so that wb_put have an extra check if wb->bdi before decrement
wb->refcnt and also add a WARN_ON_ONCE to get a warning if it happens again
in other drivers.
Fixes: 52ebea749aae ("writeback: make backing_dev_info host cgroup-specific bdi_writebacks")
Co-developed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | include/linux/backing-dev-defs.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h index 3c1beffc861a..19240379637f 100644 --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h @@ -233,6 +233,14 @@ static inline void wb_get(struct bdi_writeback *wb) */ static inline void wb_put(struct bdi_writeback *wb) { + if (WARN_ON_ONCE(!wb->bdi)) { + /* + * A driver bug might cause a file to be removed before bdi was + * initialized. + */ + return; + } + if (wb != &wb->bdi->wb) percpu_ref_put(&wb->refcnt); } |