site_archiver@lists.apple.com Delivered-To: darwin-kernel@lists.apple.com Yogesh P writes:

Hi Folks,

Hello, Yogesh,

I am working on the VFS-Lock patch on linux which gives the functionality for locking and unlocking of filesystem.

Is there any patch available on MAC for locking and unlocking of filesystem for a fraction of time????OR is the darwinkernel has VFS-Lock functionality built in????

Any pointers,reply certainly helps.

If you fail to find any existing interface to do this you can easily do this yourself: embed struct lock__bsd__ fs_lock; in your super block. In all your VFS_FOO() operations and in VOP_LOCK(vnode) do: lockmgr(&super_block->fs_lock, LK_SHARED | LK_CANRECURSE, NULL, proc); As Mac OS X kernel usually calls VOP_LOCK(vnode) before calling any other VOP operation, this will guarantee that super_block->fs_lock is taken in shared mode when file system code is entered. LK_CANRECURSE is needed, because VOP_LOCK can be called twice against the same vnode during single system call. NOTE: in a few (unfortunate) places VOP_GETATTR() is called _without_ taking vnode lock, so you will have to take super_block->fs_lock there explicitly. Now, to "lock" whole file system one just does: lockmgr(&super_block->fs_lock, LK_EXCLUSIVE, NULL, proc); Don't forget to unlock. :)

Thanks, YOGESH PAHILWAN (SOFTWARE ENGINNER)

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