mirror_zfs/config/kernel-mount-nodev.m4

dnl #
dnl # 2.6.39 API change
dnl # The .get_sb callback has been replaced by a .mount callback
dnl # in the file_system_type structure.  When using the new
dnl # interface the caller must now use the mount_nodev() helper.
dnl # This updated callback and helper no longer pass the vfsmount.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_MOUNT_NODEV],
	[AC_MSG_CHECKING([whether mount_nodev() is available])
	ZFS_LINUX_TRY_COMPILE_SYMBOL([
		#include <linux/fs.h>
	], [
		mount_nodev(NULL, 0, NULL, NULL);
	], [mount_nodev], [fs/super.c], [
		AC_MSG_RESULT(yes)
		AC_DEFINE(HAVE_MOUNT_NODEV, 1, [mount_nodev() is available])
	], [
		AC_MSG_RESULT(no)
	])
])
Linux compat 2.6.39: mount_nodev() The .get_sb callback has been replaced by a .mount callback in the file_system_type structure. When using the new interface the caller must now use the mount_nodev() helper. Unfortunately, the new interface no longer passes the vfsmount down to the zfs layers. This poses a problem for the existing implementation because we currently save this pointer in the super block for latter use. It provides our only entry point in to the namespace layer for manipulating certain mount options. This needed to be done originally to allow commands like 'zfs set atime=off tank' to work properly. It also allowed me to keep more of the original Solaris code unmodified. Under Solaris there is a 1-to-1 mapping between a mount point and a file system so this is a fairly natural thing to do. However, under Linux they many be multiple entries in the namespace which reference the same filesystem. Thus keeping a back reference from the filesystem to the namespace is complicated. Rather than introduce some ugly hack to get the vfsmount and continue as before. I'm leveraging this API change to update the ZFS code to do things in a more natural way for Linux. This has the upside that is resolves the compatibility issue for the long term and fixes several other minor bugs which have been reported. This commit updates the code to remove this vfsmount back reference entirely. All modifications to filesystem mount options are now passed in to the kernel via a '-o remount'. This is the expected Linux mechanism and allows the namespace to properly handle any options which apply to it before passing them on to the file system itself. Aside from fixing the compatibility issue, removing the vfsmount has had the benefit of simplifying the code. This change which fairly involved has turned out nicely. Closes #246 Closes #217 Closes #187 Closes #248 Closes #231 2011-05-19 22:44:07 +04:00			`dnl #`
			`dnl # 2.6.39 API change`
			`dnl # The .get_sb callback has been replaced by a .mount callback`
			`dnl # in the file_system_type structure. When using the new`
			`dnl # interface the caller must now use the mount_nodev() helper.`
			`dnl # This updated callback and helper no longer pass the vfsmount.`
			`dnl #`
When checking for symbol exports, try compiling. This patch adds a new autoconf function: ZFS_LINUX_TRY_COMPILE_SYMBOL. This new function does the following: - Call LINUX_TRY_COMPILE with the specified parameters. - If unsuccessful, return false. - If successful and we're configuring with --enable-linux-builtin, return true. - Else, call CHECK_SYMBOL_EXPORT with the specified parameters and return the result. All calls to CHECK_SYMBOL_EXPORT are converted to LINUX_TRY_COMPILE_SYMBOL so that the tests work even when configuring for builtin on a kernel which doesn't have loadable module support, or hasn't been built yet. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #851 2012-07-26 01:38:58 +04:00			`AC_DEFUN([ZFS_AC_KERNEL_MOUNT_NODEV],`
			`[AC_MSG_CHECKING([whether mount_nodev() is available])`
			`ZFS_LINUX_TRY_COMPILE_SYMBOL([`
			`#include <linux/fs.h>`
			`], [`
			`mount_nodev(NULL, 0, NULL, NULL);`
			`], [mount_nodev], [fs/super.c], [`
			`AC_MSG_RESULT(yes)`
			`AC_DEFINE(HAVE_MOUNT_NODEV, 1, [mount_nodev() is available])`
			`], [`
			`AC_MSG_RESULT(no)`
			`])`
Linux compat 2.6.39: mount_nodev() The .get_sb callback has been replaced by a .mount callback in the file_system_type structure. When using the new interface the caller must now use the mount_nodev() helper. Unfortunately, the new interface no longer passes the vfsmount down to the zfs layers. This poses a problem for the existing implementation because we currently save this pointer in the super block for latter use. It provides our only entry point in to the namespace layer for manipulating certain mount options. This needed to be done originally to allow commands like 'zfs set atime=off tank' to work properly. It also allowed me to keep more of the original Solaris code unmodified. Under Solaris there is a 1-to-1 mapping between a mount point and a file system so this is a fairly natural thing to do. However, under Linux they many be multiple entries in the namespace which reference the same filesystem. Thus keeping a back reference from the filesystem to the namespace is complicated. Rather than introduce some ugly hack to get the vfsmount and continue as before. I'm leveraging this API change to update the ZFS code to do things in a more natural way for Linux. This has the upside that is resolves the compatibility issue for the long term and fixes several other minor bugs which have been reported. This commit updates the code to remove this vfsmount back reference entirely. All modifications to filesystem mount options are now passed in to the kernel via a '-o remount'. This is the expected Linux mechanism and allows the namespace to properly handle any options which apply to it before passing them on to the file system itself. Aside from fixing the compatibility issue, removing the vfsmount has had the benefit of simplifying the code. This change which fairly involved has turned out nicely. Closes #246 Closes #217 Closes #187 Closes #248 Closes #231 2011-05-19 22:44:07 +04:00			`])`