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It appears that in earlier kernels the maximum name length of a kobject was KOBJ_NAME_LEN (20) bytes. This was later extended to dynamically allocate enough memory if it was over KOBJ_NAME_LEN, and finally it was always made dynamic. Unfortunately, util this last step happened it doesn't look like it always safe to use names larger than KOBJ_NAME_LEN. For example, under the RHEL5 2.6.18 kernel if the kobject name length exceeds KOBJ_NAME_LEN a NULL dereference is tripped. To avoid this issue the build system has been update to check to see if KOBJ_NAME_LEN is defined. If it is we have to assume the maximum kobject name length is only 20 bytes. This 20 byte name must minimally include the following components. <zpool>/<dataset>[@snapshot[partition]]
22 lines
563 B
Plaintext
22 lines
563 B
Plaintext
dnl #
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dnl # 2.6.27 API change,
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dnl # kobject KOBJ_NAME_LEN static limit removed. All users of this
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dnl # constant were removed prior to 2.6.27, but to be on the safe
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dnl # side this check ensures the constant is undefined.
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dnl #
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AC_DEFUN([ZFS_AC_KERNEL_KOBJ_NAME_LEN], [
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AC_MSG_CHECKING([whether kernel defines KOBJ_NAME_LEN])
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ZFS_LINUX_TRY_COMPILE([
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#include <linux/kobject.h>
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],[
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int val;
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val = KOBJ_NAME_LEN;
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],[
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AC_MSG_RESULT([yes])
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AC_DEFINE(HAVE_KOBJ_NAME_LEN, 1,
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[kernel defines KOBJ_NAME_LEN])
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],[
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AC_MSG_RESULT([no])
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])
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])
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