mm: move migrate_prep out from under mmap_sem (0aedadf9) · Commits · 戴 / test

Move the migrate_prep outside the mmap_sem for the following system calls 1. sys_move_pages 2. sys_migrate_pages 3. sys_mbind() It really does not matter when we flush the lru. The system is free to add pages onto the lru even during migration which will make the page migration either skip the page (mbind, migrate_pages) or return a busy state (move_pages). Fixes this lockdep warning (and potential deadlock): Some VM place has mmap_sem -> kevent_wq via lru_add_drain_all() net/core/dev.c::dev_ioctl() has rtnl_lock -> mmap_sem (*) the ioctl has copy_from_user() and it can do page fault. linkwatch_event has kevent_wq -> rtnl_lock Signed-off-by:

Christoph Lameter <cl@linux-foundation.org> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reported-by:

Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Hugh Dickins <hugh@veritas.com> Cc: Rik van Riel <riel@redhat.com> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/mempolicy.c

+11 −7

Original line number	Diff line number	Diff line
		@@ -489,12 +489,6 @@ check_range(struct mm_struct *mm, unsigned long start, unsigned long end,
		int err;
		struct vm_area_struct first, vma, *prev;

		if (flags & (MPOL_MF_MOVE \| MPOL_MF_MOVE_ALL)) {

		err = migrate_prep();
		if (err)
		return ERR_PTR(err);
		}

		first = find_vma(mm, start);
		if (!first)
		@@ -809,9 +803,13 @@ int do_migrate_pages(struct mm_struct *mm,
		const nodemask_t from_nodes, const nodemask_t to_nodes, int flags)
		{
		int busy = 0;
		int err = 0;
		int err;
		nodemask_t tmp;

		err = migrate_prep();
		if (err)
		return err;

		down_read(&mm->mmap_sem);

		err = migrate_vmas(mm, from_nodes, to_nodes, flags);
		@@ -974,6 +972,12 @@ static long do_mbind(unsigned long start, unsigned long len,
		start, start + len, mode, mode_flags,
		nmask ? nodes_addr(*nmask)[0] : -1);

		if (flags & (MPOL_MF_MOVE \| MPOL_MF_MOVE_ALL)) {

		err = migrate_prep();
		if (err)
		return err;
		}
		down_write(&mm->mmap_sem);
		vma = check_range(mm, start, end, nmask,
		flags \| MPOL_MF_INVERT, &pagelist);

mm/migrate.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -841,12 +841,12 @@ static int do_move_page_to_node_array(struct mm_struct *mm,
		struct page_to_node *pp;
		LIST_HEAD(pagelist);

		migrate_prep();
		down_read(&mm->mmap_sem);

		/*
		* Build a list of pages to migrate
		*/
		migrate_prep();
		for (pp = pm; pp->node != MAX_NUMNODES; pp++) {
		struct vm_area_struct *vma;
		struct page *page;

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