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author | Linus Walleij <linus.walleij@linaro.org> | 2016-02-19 15:36:07 +0100 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-03-29 10:11:44 -0700 |
commit | 49db08c358873af11ba3c25401de88156fa5d365 (patch) | |
tree | 1a2cddaae3f112d0239cc61841efa4b8385985e6 /include/linux/fs.h | |
parent | 00411b7b1e3ec477b75bb83ccd417c7609832db6 (diff) | |
download | op-kernel-dev-49db08c358873af11ba3c25401de88156fa5d365.zip op-kernel-dev-49db08c358873af11ba3c25401de88156fa5d365.tar.gz |
chrdev: emit a warning when we go below dynamic major range
Currently a dynamically allocated character device major is taken
from 254 and downward. This mechanism is used for RTC, IIO and a
few other subsystems.
The kernel currently has no check prevening these dynamic
allocations from eating into the assigned numbers at 233 and
downward.
In a recent test it was reported that so many dynamic device
majors were used on a test server, that the major number for
infiniband (231) was stolen. This occurred when allocating a new
major number for GPIO chips. The error messages from the kernel
were not helpful. (See: https://lkml.org/lkml/2016/2/14/124)
This patch adds a defined lower limit of the dynamic major
allocation region will henceforth emit a warning if we start to
eat into the assigned numbers. It does not do any semantic
changes and will not change the kernels behaviour: numbers will
still continue to be stolen, but we will know from dmesg what
is going on.
This also updates the Documentation/devices.txt to clearly
reflect that we are using this range of major numbers for dynamic
allocation.
Reported-by: Ying Huang <ying.huang@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux/fs.h')
-rw-r--r-- | include/linux/fs.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h index 14a9719..60082be 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2385,6 +2385,8 @@ static inline void bd_unlink_disk_holder(struct block_device *bdev, /* fs/char_dev.c */ #define CHRDEV_MAJOR_HASH_SIZE 255 +/* Marks the bottom of the first segment of free char majors */ +#define CHRDEV_MAJOR_DYN_END 234 extern int alloc_chrdev_region(dev_t *, unsigned, unsigned, const char *); extern int register_chrdev_region(dev_t, unsigned, const char *); extern int __register_chrdev(unsigned int major, unsigned int baseminor, |