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Commit 97a89413 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Linus Torvalds
Browse files

mm: Remove i_mmap_lock lockbreak 



Hugh says:
 "The only significant loser, I think, would be page reclaim (when
  concurrent with truncation): could spin for a long time waiting for
  the i_mmap_mutex it expects would soon be dropped? "

Counter points:
 - cpu contention makes the spin stop (need_resched())
 - zap pages should be freeing pages at a higher rate than reclaim
   ever can

I think the simplification of the truncate code is definitely worth it.

Effectively reverts: 2aa15890 ("mm: prevent concurrent
unmap_mapping_range() on the same inode") and takes out the code that
caused its problem.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Miller <davem@davemloft.net>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e4c70a66

fs/inode.c

+0 −1
Original line number Diff line number Diff line
@@ -331,7 +331,6 @@ void address_space_init_once(struct address_space *mapping) 
	spin_lock_init(&mapping->private_lock);

	INIT_RAW_PRIO_TREE_ROOT(&mapping->i_mmap);

	INIT_LIST_HEAD(&mapping->i_mmap_nonlinear);

	mutex_init(&mapping->unmap_mutex);

}

EXPORT_SYMBOL(address_space_init_once);

include/linux/fs.h

+0 −2
Original line number Diff line number Diff line
@@ -635,7 +635,6 @@ struct address_space { 
	struct prio_tree_root	i_mmap;		/* tree of private and shared mappings */

	struct list_head	i_mmap_nonlinear;/*list VM_NONLINEAR mappings */

	spinlock_t		i_mmap_lock;	/* protect tree, count, list */

	unsigned int		truncate_count;	/* Cover race condition with truncate */

	unsigned long		nrpages;	/* number of total pages */

	pgoff_t			writeback_index;/* writeback starts here */

	const struct address_space_operations *a_ops;	/* methods */
@@ -644,7 +643,6 @@ struct address_space { 
	spinlock_t		private_lock;	/* for use by the address_space */

	struct list_head	private_list;	/* ditto */

	struct address_space	*assoc_mapping;	/* ditto */

	struct mutex		unmap_mutex;    /* to protect unmapping */

} __attribute__((aligned(sizeof(long))));

	/*

	 * On most architectures that alignment is already the case; but

include/linux/mm.h

+0 −2
Original line number Diff line number Diff line
@@ -895,8 +895,6 @@ struct zap_details { 
	struct address_space *check_mapping;	/* Check page->mapping if set */

	pgoff_t	first_index;			/* Lowest page->index to unmap */

	pgoff_t last_index;			/* Highest page->index to unmap */

	spinlock_t *i_mmap_lock;		/* For unmap_mapping_range: */

	unsigned long truncate_count;		/* Compare vm_truncate_count */

};



struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,

include/linux/mm_types.h

+0 −1
Original line number Diff line number Diff line
@@ -175,7 +175,6 @@ struct vm_area_struct { 
					   units, *not* PAGE_CACHE_SIZE */

	struct file * vm_file;		/* File we map to (can be NULL). */

	void * vm_private_data;		/* was vm_pte (shared mem) */

	unsigned long vm_truncate_count;/* truncate_count or restart_addr */



#ifndef CONFIG_MMU

	struct vm_region *vm_region;	/* NOMMU mapping region */

kernel/fork.c

+0 −1
Original line number Diff line number Diff line
@@ -386,7 +386,6 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 
			spin_lock(&mapping->i_mmap_lock);

			if (tmp->vm_flags & VM_SHARED)

				mapping->i_mmap_writable++;

			tmp->vm_truncate_count = mpnt->vm_truncate_count;

			flush_dcache_mmap_lock(mapping);

			/* insert tmp into the share list, just after mpnt */

			vma_prio_tree_add(tmp, mpnt);