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Commit fc8744ad authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Stop playing silly games with the VM_ACCOUNT flag 



The mmap_region() code would temporarily set the VM_ACCOUNT flag for
anonymous shared mappings just to inform shmem_zero_setup() that it
should enable accounting for the resulting shm object.  It would then
clear the flag after calling ->mmap (for the /dev/zero case) or doing
shmem_zero_setup() (for the MAP_ANON case).

This just resulted in vma merge issues, but also made for just
unnecessary confusion.  Use the already-existing VM_NORESERVE flag for
this instead, and let shmem_{zero|file}_setup() just figure it out from
that.

This also happens to make it obvious that the new DRI2 GEM layer uses a
non-reserving backing store for its object allocation - which is quite
possibly not intentional.  But since I didn't want to change semantics
in this patch, I left it alone, and just updated the caller to use the
new flag semantics.

Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 33bfad54

drivers/gpu/drm/drm_gem.c

+1 −1
Original line number Diff line number Diff line
@@ -136,7 +136,7 @@ drm_gem_object_alloc(struct drm_device *dev, size_t size) 
	obj = kcalloc(1, sizeof(*obj), GFP_KERNEL);



	obj->dev = dev;

	obj->filp = shmem_file_setup("drm mm object", size, 0);

	obj->filp = shmem_file_setup("drm mm object", size, VM_NORESERVE);

	if (IS_ERR(obj->filp)) {

		kfree(obj);

		return NULL;

ipc/shm.c

+2 −2
Original line number Diff line number Diff line
@@ -368,14 +368,14 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params) 
		file = hugetlb_file_setup(name, size);

		shp->mlock_user = current_user();

	} else {

		int acctflag = VM_ACCOUNT;

		int acctflag = 0;

		/*

		 * Do not allow no accounting for OVERCOMMIT_NEVER, even

	 	 * if it's asked for.

		 */

		if  ((shmflg & SHM_NORESERVE) &&

				sysctl_overcommit_memory != OVERCOMMIT_NEVER)

			acctflag = 0;

			acctflag = VM_NORESERVE;

		file = shmem_file_setup(name, size, acctflag);

	}

	error = PTR_ERR(file);

mm/mmap.c

+25 −23
Original line number Diff line number Diff line
@@ -1090,6 +1090,15 @@ int vma_wants_writenotify(struct vm_area_struct *vma) 
		mapping_cap_account_dirty(vma->vm_file->f_mapping);

}



/*

 * We account for memory if it's a private writeable mapping,

 * and VM_NORESERVE wasn't set.

 */

static inline int accountable_mapping(unsigned int vm_flags)

{

	return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;

}



unsigned long mmap_region(struct file *file, unsigned long addr,

			  unsigned long len, unsigned long flags,

			  unsigned int vm_flags, unsigned long pgoff,
@@ -1117,24 +1126,25 @@ unsigned long mmap_region(struct file *file, unsigned long addr, 
	if (!may_expand_vm(mm, len >> PAGE_SHIFT))

		return -ENOMEM;



	if (flags & MAP_NORESERVE)

	/*

	 * Set 'VM_NORESERVE' if we should not account for the

	 * memory use of this mapping. We only honor MAP_NORESERVE

	 * if we're allowed to overcommit memory.

	 */

	if ((flags & MAP_NORESERVE) && sysctl_overcommit_memory != OVERCOMMIT_NEVER)

		vm_flags |= VM_NORESERVE;

	if (!accountable)

		vm_flags |= VM_NORESERVE;



	if (accountable && (!(flags & MAP_NORESERVE) ||

			    sysctl_overcommit_memory == OVERCOMMIT_NEVER)) {

		if (vm_flags & VM_SHARED) {

			/* Check memory availability in shmem_file_setup? */

			vm_flags |= VM_ACCOUNT;

		} else if (vm_flags & VM_WRITE) {

	/*

	 * Private writable mapping: check memory availability

	 */

	if (accountable_mapping(vm_flags)) {

		charged = len >> PAGE_SHIFT;

		if (security_vm_enough_memory(charged))

			return -ENOMEM;

		vm_flags |= VM_ACCOUNT;

	}

	}



	/*

	 * Can we just expand an old mapping?
@@ -1184,14 +1194,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr, 
			goto free_vma;

	}



	/* We set VM_ACCOUNT in a shared mapping's vm_flags, to inform

	 * shmem_zero_setup (perhaps called through /dev/zero's ->mmap)

	 * that memory reservation must be checked; but that reservation

	 * belongs to shared memory object, not to vma: so now clear it.

	 */

	if ((vm_flags & (VM_SHARED|VM_ACCOUNT)) == (VM_SHARED|VM_ACCOUNT))

		vma->vm_flags &= ~VM_ACCOUNT;



	/* Can addr have changed??

	 *

	 * Answer: Yes, several device drivers can do it in their

mm/shmem.c

+1 −1
Original line number Diff line number Diff line
@@ -2628,7 +2628,7 @@ struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags) 
		goto close_file;



#ifdef CONFIG_SHMEM

	SHMEM_I(inode)->flags = flags & VM_ACCOUNT;

	SHMEM_I(inode)->flags = (flags & VM_NORESERVE) ? 0 : VM_ACCOUNT;

#endif

	d_instantiate(dentry, inode);

	inode->i_size = size;