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kernel/fork: use maple tree for dup_mmap() during forking

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The maple tree was already tracking VMAs in this function by an earlier
commit, but the rbtree iterator was being used to iterate the list.
Change the iterator to use a maple tree native iterator and switch to the
maple tree advanced API to avoid multiple walks of the tree during insert
operations.  Unexport the now-unused vma_store() function.

For performance reasons we bulk allocate the maple tree nodes.  The node
calculations are done internally to the tree and use the VMA count and
assume the worst-case node requirements.  The VM_DONT_COPY flag does not
allow for the most efficient copy method of the tree and so a bulk loading
algorithm is used.

Link: https://lkml.kernel.org/r/20220906194824.2110408-15-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Liam R. Howlett 2022-09-06 19:48:47 +00:00 committed by Andrew Morton
parent 3499a13168
commit c9dbe82cb9
2 changed files with 13 additions and 4 deletions
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2
include/linux/mm.h
View File

@ -2599,8 +2599,6 @@ extern bool arch_has_descending_max_zone_pfns(void);
/* nommu.c */
extern atomic_long_t mmap_pages_allocated;
extern int nommu_shrink_inode_mappings(struct inode *, size_t, size_t);
/* mmap.c */
void vma_mas_store(struct vm_area_struct *vma, struct ma_state *mas);
/* interval_tree.c */
void vma_interval_tree_insert(struct vm_area_struct *node,

15
kernel/fork.c
View File

@ -583,8 +583,9 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
struct rb_node **rb_link, *rb_parent;
int retval;
unsigned long charge;
unsigned long charge = 0;
LIST_HEAD(uf);
MA_STATE(old_mas, &oldmm->mm_mt, 0, 0);
MA_STATE(mas, &mm->mm_mt, 0, 0);
uprobe_start_dup_mmap();
@ -620,7 +621,12 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
goto out;
prev = NULL;
for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
retval = mas_expected_entries(&mas, oldmm->map_count);
if (retval)
goto out;
mas_for_each(&old_mas, mpnt, ULONG_MAX) {
struct file *file;
if (mpnt->vm_flags & VM_DONTCOPY) {
@ -703,6 +709,8 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
mas.index = tmp->vm_start;
mas.last = tmp->vm_end - 1;
mas_store(&mas, tmp);
if (mas_is_err(&mas))
goto fail_nomem_mas_store;
mm->map_count++;
if (!(tmp->vm_flags & VM_WIPEONFORK))
@ -726,6 +734,9 @@ out:
fail_uprobe_end:
uprobe_end_dup_mmap();
return retval;
fail_nomem_mas_store:
unlink_anon_vmas(tmp);
fail_nomem_anon_vma_fork:
mpol_put(vma_policy(tmp));
fail_nomem_policy: