diff options
| author | Linus Walleij <linus.walleij@linaro.org> | 2016-02-19 15:36:07 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-03-29 10:11:44 -0700 |
| commit | 49db08c358873af11ba3c25401de88156fa5d365 (patch) | |
| tree | 1a2cddaae3f112d0239cc61841efa4b8385985e6 /fs/char_dev.c | |
| parent | 00411b7b1e3ec477b75bb83ccd417c7609832db6 (diff) | |
| download | linux-riscv-49db08c358873af11ba3c25401de88156fa5d365.tar.gz linux-riscv-49db08c358873af11ba3c25401de88156fa5d365.tar.bz2 linux-riscv-49db08c358873af11ba3c25401de88156fa5d365.zip | |
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 'fs/char_dev.c')
| -rw-r--r-- | fs/char_dev.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/char_dev.c b/fs/char_dev.c index 24b142569ca9..687471dc04a0 100644 --- a/fs/char_dev.c +++ b/fs/char_dev.c @@ -91,6 +91,10 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor, break; } + if (i < CHRDEV_MAJOR_DYN_END) + pr_warn("CHRDEV \"%s\" major number %d goes below the dynamic allocation range", + name, i); + if (i == 0) { ret = -EBUSY; goto out; |