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Revert "ANDROID: mm: use raw seqcount variants in vm_write_*"

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This reverts commit f2c1ef71ed.

Change-Id: I5dc242f3d5aa05eb4630426d7444c36412ed6191
Signed-off-by: Alexander Winkowski <dereference23@outlook.com>
This commit is contained in:
Alexander Winkowski 2024-01-12 05:02:10 +00:00
commit 5f80d03c8c
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GPG key ID: 72762A66704CDE44
3 changed files with 57 additions and 18 deletions
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29
include/linux/mm.h
View file

@ -1613,13 +1613,22 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
#ifdef CONFIG_SPECULATIVE_PAGE_FAULT
static inline void vm_write_begin(struct vm_area_struct *vma)
{
/*
* The reads never spins and preemption
* disablement is not required.
*/
raw_write_seqcount_begin(&vma->vm_sequence);
write_seqcount_begin(&vma->vm_sequence);
}
static inline void vm_write_begin_nested(struct vm_area_struct *vma,
int subclass)
{
write_seqcount_begin_nested(&vma->vm_sequence, subclass);
}
static inline void vm_write_end(struct vm_area_struct *vma)
{
write_seqcount_end(&vma->vm_sequence);
}
static inline void vm_raw_write_begin(struct vm_area_struct *vma)
{
raw_write_seqcount_begin(&vma->vm_sequence);
}
static inline void vm_raw_write_end(struct vm_area_struct *vma)
{
raw_write_seqcount_end(&vma->vm_sequence);
}
@ -1627,9 +1636,19 @@ static inline void vm_write_end(struct vm_area_struct *vma)
static inline void vm_write_begin(struct vm_area_struct *vma)
{
}
static inline void vm_write_begin_nested(struct vm_area_struct *vma,
int subclass)
{
}
static inline void vm_write_end(struct vm_area_struct *vma)
{
}
static inline void vm_raw_write_begin(struct vm_area_struct *vma)
{
}
static inline void vm_raw_write_end(struct vm_area_struct *vma)
{
}
#endif /* CONFIG_SPECULATIVE_PAGE_FAULT */
extern void truncate_pagecache(struct inode *inode, loff_t new);

38
mm/mmap.c
View file

@ -767,9 +767,29 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
long adjust_next = 0;
int remove_next = 0;
vm_write_begin(vma);
/*
* Why using vm_raw_write*() functions here to avoid lockdep's warning ?
*
* Locked is complaining about a theoretical lock dependency, involving
* 3 locks:
* mapping->i_mmap_rwsem --> vma->vm_sequence --> fs_reclaim
*
* Here are the major path leading to this dependency :
* 1. __vma_adjust() mmap_sem -> vm_sequence -> i_mmap_rwsem
* 2. move_vmap() mmap_sem -> vm_sequence -> fs_reclaim
* 3. __alloc_pages_nodemask() fs_reclaim -> i_mmap_rwsem
* 4. unmap_mapping_range() i_mmap_rwsem -> vm_sequence
*
* So there is no way to solve this easily, especially because in
* unmap_mapping_range() the i_mmap_rwsem is grab while the impacted
* VMAs are not yet known.
* However, the way the vm_seq is used is guarantying that we will
* never block on it since we just check for its value and never wait
* for it to move, see vma_has_changed() and handle_speculative_fault().
*/
vm_raw_write_begin(vma);
if (next)
vm_write_begin(next);
vm_raw_write_begin(next);
if (next && !insert) {
struct vm_area_struct *exporter = NULL, *importer = NULL;
@ -853,8 +873,8 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
error = anon_vma_clone(importer, exporter);
if (error) {
if (next && next != vma)
vm_write_end(next);
vm_write_end(vma);
vm_raw_write_end(next);
vm_raw_write_end(vma);
return error;
}
}
@ -983,7 +1003,7 @@ again:
if (next->anon_vma)
anon_vma_merge(vma, next);
mm->map_count--;
vm_write_end(next);
vm_raw_write_end(next);
put_vma(next);
/*
* In mprotect's case 6 (see comments on vma_merge),
@ -999,7 +1019,7 @@ again:
*/
next = vma->vm_next;
if (next)
vm_write_begin(next);
vm_raw_write_begin(next);
} else {
/*
* For the scope of the comment "next" and
@ -1047,9 +1067,9 @@ again:
uprobe_mmap(insert);
if (next && next != vma)
vm_write_end(next);
vm_raw_write_end(next);
if (!keep_locked)
vm_write_end(vma);
vm_raw_write_end(vma);
validate_mm(mm);
@ -3409,7 +3429,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
* that we protect it right now, and let the caller unprotect
* it once the move is done.
*/
vm_write_begin(new_vma);
vm_raw_write_begin(new_vma);
vma_link(mm, new_vma, prev, rb_link, rb_parent);
*need_rmap_locks = false;
}

8
mm/mremap.c
View file

@ -533,7 +533,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,
* to be mapped in our back while we are copying the PTEs.
*/
if (vma != new_vma)
vm_write_begin(vma);
vm_raw_write_begin(vma);
moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
need_rmap_locks);
@ -552,7 +552,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,
move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
true);
if (vma != new_vma)
vm_write_end(vma);
vm_raw_write_end(vma);
vma = new_vma;
old_len = new_len;
old_addr = new_addr;
@ -562,9 +562,9 @@ static unsigned long move_vma(struct vm_area_struct *vma,
arch_remap(mm, old_addr, old_addr + old_len,
new_addr, new_addr + new_len);
if (vma != new_vma)
vm_write_end(vma);
vm_raw_write_end(vma);
}
vm_write_end(new_vma);
vm_raw_write_end(new_vma);
/* Conceal VM_ACCOUNT so old reservation is not undone */
if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) {