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authorLinus Walleij <linus.walleij@linaro.org>2016-02-19 15:36:07 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-03-29 10:11:44 -0700
commit49db08c358873af11ba3c25401de88156fa5d365 (patch)
tree1a2cddaae3f112d0239cc61841efa4b8385985e6 /fs/char_dev.c
parent00411b7b1e3ec477b75bb83ccd417c7609832db6 (diff)
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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.c4
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;