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Eric W. Biederman bc56bba8f3 [PATCH] shm: make sysv ipc shared memory use stacked files ... The current ipc shared memory code runs into several problems because it does not quite use files like the rest of the kernel. With the option of backing ipc shared memory with either hugetlbfs or ordinary shared memory the problems got worse. With the added support for ipc namespaces things behaved so unexpected that we now have several bad namespace reference counting bugs when using what appears at first glance to be a reasonable idiom. So to attack these problems and hopefully make the code more maintainable this patch simply uses the files provided by other parts of the kernel and builds it's own files out of them. The shm files are allocated in do_shmat and freed when their reference count drops to zero with their last unmap. The file and vm operations that we don't want to implement or we don't implement completely we just delegate to the operations of our backing file. This means that we now get an accurate shm_nattch count for we have a hugetlbfs inode for backing store, and the shm accounting of last attach and last detach time work as well. This means that getting a reference to the ipc namespace when we create the file and dropping the referenece in the release method is now safe and correct. This means we no longer need a special case for clearing VM_MAYWRITE as our file descriptor now only has write permissions when we have requested write access when calling shmat. Although VM_SHARED is now cleared as well which I believe is harmless and is mostly likely a minor bug fix. By using the same set of operations for both the hugetlb case and regular shared memory case shmdt is not simplified and made slightly more correct as now the test "vma->vm_ops == &shm_vm_ops" is 100% accurate in spotting all shared memory regions generated from sysvipc shared memory. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Cc: Michal Piotrowski <michal.k.k.piotrowski@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		18 years ago
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Makefile	[PATCH] sysctl: move SYSV IPC sysctls to their own file	18 years ago
compat.c	[PATCH] Fix the size limit of compat space msgsize	18 years ago
compat_mq.c	Linux-2.6.12-rc2	20 years ago
ipc_sysctl.c	[PATCH] sysctl: remove insert_at_head from register_sysctl	18 years ago
mqueue.c	[PATCH] sysctl: remove insert_at_head from register_sysctl	18 years ago
msg.c	[PATCH] Fix the size limit of compat space msgsize	18 years ago
msgutil.c	[PATCH] getting rid of all casts of k[cmz]alloc() calls	18 years ago
sem.c	[PATCH] kernel core: replace kmalloc+memset with kzalloc	18 years ago
shm.c	[PATCH] shm: make sysv ipc shared memory use stacked files	18 years ago
util.c	[PATCH] mark struct file_operations const 7	18 years ago
util.h	[PATCH] Fix ipc entries removal	19 years ago