Commit 7ee78232 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
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[PATCH] mm: dup_mmap down new mmap_sem



One anomaly remains from when Andrea rationalized the responsibilities of
mmap_sem and page_table_lock: in dup_mmap we add vmas to the child holding its
page_table_lock, but not the mmap_sem which normally guards the vma list and
rbtree.  Which could be an issue for unuse_mm: though since it just walks down
the list (today with page_table_lock, tomorrow not), it's probably okay.  Will
need a memory barrier?  Oh, keep it simple, Nick and I agreed, no harm in
taking child's mmap_sem here.
Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent fd3e42fc
...@@ -192,6 +192,8 @@ static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) ...@@ -192,6 +192,8 @@ static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
down_write(&oldmm->mmap_sem); down_write(&oldmm->mmap_sem);
flush_cache_mm(oldmm); flush_cache_mm(oldmm);
down_write(&mm->mmap_sem);
mm->locked_vm = 0; mm->locked_vm = 0;
mm->mmap = NULL; mm->mmap = NULL;
mm->mmap_cache = NULL; mm->mmap_cache = NULL;
...@@ -251,10 +253,7 @@ static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) ...@@ -251,10 +253,7 @@ static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
} }
/* /*
* Link in the new vma and copy the page table entries: * Link in the new vma and copy the page table entries.
* link in first so that swapoff can see swap entries.
* Note that, exceptionally, here the vma is inserted
* without holding mm->mmap_sem.
*/ */
spin_lock(&mm->page_table_lock); spin_lock(&mm->page_table_lock);
*pprev = tmp; *pprev = tmp;
...@@ -275,8 +274,8 @@ static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) ...@@ -275,8 +274,8 @@ static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
goto out; goto out;
} }
retval = 0; retval = 0;
out: out:
up_write(&mm->mmap_sem);
flush_tlb_mm(oldmm); flush_tlb_mm(oldmm);
up_write(&oldmm->mmap_sem); up_write(&oldmm->mmap_sem);
return retval; return retval;
......
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