Revision 3f758e844aa9800eb660d60ee10226fa802594d4 authored by Paolo Valente on 07 August 2019, 14:17:54 UTC, committed by Jens Axboe on 08 August 2019, 13:30:52 UTC
Since commit 13a857a4c4e8 ("block, bfq: detect wakers and unconditionally inject their I/O"), every bfq_queue has a pointer to a waker bfq_queue and a list of the bfq_queues it may wake. In this respect, when a bfq_queue, say Q, remains with no I/O source attached to it, Q cannot be woken by any other bfq_queue, and cannot wake any other bfq_queue. Then Q must be removed from the woken list of its possible waker bfq_queue, and all bfq_queues in the woken list of Q must stop having a waker bfq_queue. Q remains with no I/O source in two cases: when the last process associated with Q exits or when such a process gets associated with a different bfq_queue. Unfortunately, commit 13a857a4c4e8 ("block, bfq: detect wakers and unconditionally inject their I/O") performed the above updates only in the first case. This commit fixes this bug by moving these updates to when Q gets freed. This is a simple and safe way to handle all cases, as both the above events, process exit and re-association, lead to Q being freed soon, and because dangling references would come out only after Q gets freed (if no update were performed). Fixes: 13a857a4c4e8 ("block, bfq: detect wakers and unconditionally inject their I/O") Reported-by: Douglas Anderson <dianders@chromium.org> Tested-by: Douglas Anderson <dianders@chromium.org> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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interval_tree.c
// SPDX-License-Identifier: GPL-2.0-only
/*
* mm/interval_tree.c - interval tree for mapping->i_mmap
*
* Copyright (C) 2012, Michel Lespinasse <walken@google.com>
*/
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/rmap.h>
#include <linux/interval_tree_generic.h>
static inline unsigned long vma_start_pgoff(struct vm_area_struct *v)
{
return v->vm_pgoff;
}
static inline unsigned long vma_last_pgoff(struct vm_area_struct *v)
{
return v->vm_pgoff + vma_pages(v) - 1;
}
INTERVAL_TREE_DEFINE(struct vm_area_struct, shared.rb,
unsigned long, shared.rb_subtree_last,
vma_start_pgoff, vma_last_pgoff,, vma_interval_tree)
/* Insert node immediately after prev in the interval tree */
void vma_interval_tree_insert_after(struct vm_area_struct *node,
struct vm_area_struct *prev,
struct rb_root_cached *root)
{
struct rb_node **link;
struct vm_area_struct *parent;
unsigned long last = vma_last_pgoff(node);
VM_BUG_ON_VMA(vma_start_pgoff(node) != vma_start_pgoff(prev), node);
if (!prev->shared.rb.rb_right) {
parent = prev;
link = &prev->shared.rb.rb_right;
} else {
parent = rb_entry(prev->shared.rb.rb_right,
struct vm_area_struct, shared.rb);
if (parent->shared.rb_subtree_last < last)
parent->shared.rb_subtree_last = last;
while (parent->shared.rb.rb_left) {
parent = rb_entry(parent->shared.rb.rb_left,
struct vm_area_struct, shared.rb);
if (parent->shared.rb_subtree_last < last)
parent->shared.rb_subtree_last = last;
}
link = &parent->shared.rb.rb_left;
}
node->shared.rb_subtree_last = last;
rb_link_node(&node->shared.rb, &parent->shared.rb, link);
rb_insert_augmented(&node->shared.rb, &root->rb_root,
&vma_interval_tree_augment);
}
static inline unsigned long avc_start_pgoff(struct anon_vma_chain *avc)
{
return vma_start_pgoff(avc->vma);
}
static inline unsigned long avc_last_pgoff(struct anon_vma_chain *avc)
{
return vma_last_pgoff(avc->vma);
}
INTERVAL_TREE_DEFINE(struct anon_vma_chain, rb, unsigned long, rb_subtree_last,
avc_start_pgoff, avc_last_pgoff,
static inline, __anon_vma_interval_tree)
void anon_vma_interval_tree_insert(struct anon_vma_chain *node,
struct rb_root_cached *root)
{
#ifdef CONFIG_DEBUG_VM_RB
node->cached_vma_start = avc_start_pgoff(node);
node->cached_vma_last = avc_last_pgoff(node);
#endif
__anon_vma_interval_tree_insert(node, root);
}
void anon_vma_interval_tree_remove(struct anon_vma_chain *node,
struct rb_root_cached *root)
{
__anon_vma_interval_tree_remove(node, root);
}
struct anon_vma_chain *
anon_vma_interval_tree_iter_first(struct rb_root_cached *root,
unsigned long first, unsigned long last)
{
return __anon_vma_interval_tree_iter_first(root, first, last);
}
struct anon_vma_chain *
anon_vma_interval_tree_iter_next(struct anon_vma_chain *node,
unsigned long first, unsigned long last)
{
return __anon_vma_interval_tree_iter_next(node, first, last);
}
#ifdef CONFIG_DEBUG_VM_RB
void anon_vma_interval_tree_verify(struct anon_vma_chain *node)
{
WARN_ON_ONCE(node->cached_vma_start != avc_start_pgoff(node));
WARN_ON_ONCE(node->cached_vma_last != avc_last_pgoff(node));
}
#endif
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