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Commit 2af548dd authored by Brian Geffon's avatar Brian Geffon Committed by Michael Bestas
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BACKPORT: FROMLIST: Revert "mremap: don't allow MREMAP_DONTUNMAP on special_mappings and aio" 

This reverts commit cd544fd1dc9293c6702fab6effa63dac1cc67e99.

As discussed in [1] this commit was a no-op because the mapping type was
checked in vma_to_resize before move_vma is ever called. This meant that
vm_ops->mremap() would never be called on such mappings. Furthermore,
we've since expanded support of MREMAP_DONTUNMAP to non-anonymous
mappings, and these special mappings are still protected by the existing
check of !VM_DONTEXPAND and !VM_PFNMAP which will result in a -EINVAL.

1. https://lkml.org/lkml/2020/12/28/2340



Signed-off-by: default avatarBrian Geffon <bgeffon@google.com>
Acked-by: default avatarHugh Dickins <hughd@google.com>
Reviewed-by: default avatarDmitry Safonov <0x7f454c46@gmail.com>

Signed-off-by: default avatarLokesh Gidra <lokeshgidra@google.com>
Link: https://lore.kernel.org/patchwork/patch/1401226/
Conflicts: include/linux/mm.h
(Resolved minor conflict with manual rebase)
Bug: 160737021
Bug: 169683130
Change-Id: I97d29e6a54cee07ba69d6bb880778ee1fea8ff7c
parent 7629defa

arch/x86/kernel/cpu/resctrl/pseudo_lock.c

+1 −1
Original line number Diff line number Diff line
@@ -1464,7 +1464,7 @@ static int pseudo_lock_dev_release(struct inode *inode, struct file *filp) 
	return 0;

}



static int pseudo_lock_dev_mremap(struct vm_area_struct *area, unsigned long flags)

static int pseudo_lock_dev_mremap(struct vm_area_struct *area)

{

	/* Not supported */

	return -EINVAL;

fs/aio.c

+1 −4
Original line number Diff line number Diff line
@@ -320,16 +320,13 @@ static void aio_free_ring(struct kioctx *ctx) 
	}

}



static int aio_ring_mremap(struct vm_area_struct *vma, unsigned long flags)

static int aio_ring_mremap(struct vm_area_struct *vma)

{

	struct file *file = vma->vm_file;

	struct mm_struct *mm = vma->vm_mm;

	struct kioctx_table *table;

	int i, res = -EINVAL;



	if (flags & MREMAP_DONTUNMAP)

		return -EINVAL;



	spin_lock(&mm->ioctx_lock);

	rcu_read_lock();

	table = rcu_dereference(mm->ioctx_table);

include/linux/mm.h

+1 −1
Original line number Diff line number Diff line
@@ -499,7 +499,7 @@ struct vm_operations_struct { 
	void (*open)(struct vm_area_struct * area);

	void (*close)(struct vm_area_struct * area);

	int (*split)(struct vm_area_struct * area, unsigned long addr);

	int (*mremap)(struct vm_area_struct *area, unsigned long flags);

	int (*mremap)(struct vm_area_struct *area);

	vm_fault_t (*fault)(struct vm_fault *vmf);

	vm_fault_t (*huge_fault)(struct vm_fault *vmf,

			enum page_entry_size pe_size);

mm/mmap.c

+1 −5
Original line number Diff line number Diff line
@@ -3492,14 +3492,10 @@ static const char *special_mapping_name(struct vm_area_struct *vma) 
	return ((struct vm_special_mapping *)vma->vm_private_data)->name;

}



static int special_mapping_mremap(struct vm_area_struct *new_vma,

				  unsigned long flags)

static int special_mapping_mremap(struct vm_area_struct *new_vma)

{

	struct vm_special_mapping *sm = new_vma->vm_private_data;



	if (flags & MREMAP_DONTUNMAP)

		return -EINVAL;



	if (WARN_ON_ONCE(current->mm != new_vma->vm_mm))

		return -EFAULT;

mm/mremap.c

+1 −1
Original line number Diff line number Diff line
@@ -577,7 +577,7 @@ static unsigned long move_vma(struct vm_area_struct *vma, 
	if (moved_len < old_len) {

		err = -ENOMEM;

	} else if (vma->vm_ops && vma->vm_ops->mremap) {

		err = vma->vm_ops->mremap(new_vma, flags);

		err = vma->vm_ops->mremap(new_vma);

	}



	if (unlikely(err)) {