apfs/linux-apfs
0
0
Fork 0
mirror of https://github.com/linux-apfs/linux-apfs.git synced 2026-05-01 15:00:59 -07:00
Code Issues Packages Projects Releases Wiki Activity

[PATCH] mm: ptd_alloc take ptlock

Browse Source 
Second step in pushing down the page_table_lock.  Remove the temporary
bridging hack from __pud_alloc, __pmd_alloc, __pte_alloc: expect callers not
to hold page_table_lock, whether it's on init_mm or a user mm; take
page_table_lock internally to check if a racing task already allocated.

Convert their callers from common code.  But avoid coming back to change them
again later: instead of moving the spin_lock(&mm->page_table_lock) down,
switch over to new macros pte_alloc_map_lock and pte_unmap_unlock, which
encapsulate the mapping+locking and unlocking+unmapping together, and in the
end may use alternatives to the mm page_table_lock itself.

These callers all hold mmap_sem (some exclusively, some not), so at no level
can a page table be whipped away from beneath them; and pte_alloc uses the
"atomic" pmd_present to test whether it needs to allocate.  It appears that on
all arches we can safely descend without page_table_lock.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Hugh Dickins
2005-10-29 18:16:23 -07:00
committed by Linus Torvalds
parent 1bb3630e89
commit c74df32c72
7 changed files with 90 additions and 135 deletions
Download Patch File Download Diff File Expand all files Collapse all files
mm/mremap.c
+9 -18
View File
@@ -28,9 +28,6 @@ static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
pud_t *pud;
pmd_t *pmd;
/*
* We don't need page_table_lock: we have mmap_sem exclusively.
*/
pgd = pgd_offset(mm, addr);
if (pgd_none_or_clear_bad(pgd))
return NULL;
@@ -50,25 +47,20 @@ static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr)
{
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd = NULL;
pmd_t *pmd;
/*
* We do need page_table_lock: because allocators expect that.
*/
spin_lock(&mm->page_table_lock);
pgd = pgd_offset(mm, addr);
pud = pud_alloc(mm, pgd, addr);
if (!pud)
goto out;
return NULL;
pmd = pmd_alloc(mm, pud, addr);
if (!pmd)
goto out;
return NULL;
if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr))
pmd = NULL;
out:
spin_unlock(&mm->page_table_lock);
return NULL;
return pmd;
}
@@ -80,6 +72,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
struct address_space *mapping = NULL;
struct mm_struct *mm = vma->vm_mm;
pte_t *old_pte, *new_pte, pte;
spinlock_t *old_ptl;
if (vma->vm_file) {
/*
@@ -95,9 +88,8 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
new_vma->vm_truncate_count = 0;
}
spin_lock(&mm->page_table_lock);
old_pte = pte_offset_map(old_pmd, old_addr);
new_pte = pte_offset_map_nested(new_pmd, new_addr);
old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
new_pte = pte_offset_map_nested(new_pmd, new_addr);
for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
new_pte++, new_addr += PAGE_SIZE) {
@@ -110,8 +102,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
}
pte_unmap_nested(new_pte - 1);
pte_unmap(old_pte - 1);
spin_unlock(&mm->page_table_lock);
pte_unmap_unlock(old_pte - 1, old_ptl);
if (mapping)
spin_unlock(&mapping->i_mmap_lock);
}