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dax fixes for 5.13-rc2 

- Fix a hang condition (missed wakeups with virtiofs when invalidating
   entries)
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Merge tag 'dax-fixes-5.13-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm

Pull dax fixes from Dan Williams:
 "A fix for a hang condition due to missed wakeups in the filesystem-dax
  core when exercised by virtiofs.

  This bug has been there from the beginning, but the condition has
  not triggered on other filesystems since they hold a lock over
  invalidation events"

* tag 'dax-fixes-5.13-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  dax: Wake up all waiters after invalidating dax entry
  dax: Add a wakeup mode parameter to put_unlocked_entry()
  dax: Add an enum for specifying dax wakup mode
This commit is contained in:
Linus Torvalds 2021-05-15 08:28:08 -07:00
parent 33f85ca44e 237388320d
commit 393f42f113
1 changed files with 23 additions and 12 deletions
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35
fs/dax.c
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@ -144,6 +144,16 @@ struct wait_exceptional_entry_queue {
struct exceptional_entry_key key;
};
/**
* enum dax_wake_mode: waitqueue wakeup behaviour
* @WAKE_ALL: wake all waiters in the waitqueue
* @WAKE_NEXT: wake only the first waiter in the waitqueue
*/
enum dax_wake_mode {
WAKE_ALL,
WAKE_NEXT,
};
static wait_queue_head_t *dax_entry_waitqueue(struct xa_state *xas,
void *entry, struct exceptional_entry_key *key)
{
@ -182,7 +192,8 @@ static int wake_exceptional_entry_func(wait_queue_entry_t *wait,
* The important information it's conveying is whether the entry at
* this index used to be a PMD entry.
*/
static void dax_wake_entry(struct xa_state *xas, void *entry, bool wake_all)
static void dax_wake_entry(struct xa_state *xas, void *entry,
enum dax_wake_mode mode)
{
struct exceptional_entry_key key;
wait_queue_head_t *wq;
@ -196,7 +207,7 @@ static void dax_wake_entry(struct xa_state *xas, void *entry, bool wake_all)
* must be in the waitqueue and the following check will see them.
*/
if (waitqueue_active(wq))
__wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
__wake_up(wq, TASK_NORMAL, mode == WAKE_ALL ? 0 : 1, &key);
}
/*
@ -264,11 +275,11 @@ static void wait_entry_unlocked(struct xa_state *xas, void *entry)
finish_wait(wq, &ewait.wait);
}
static void put_unlocked_entry(struct xa_state *xas, void *entry)
static void put_unlocked_entry(struct xa_state *xas, void *entry,
enum dax_wake_mode mode)
{
/* If we were the only waiter woken, wake the next one */
if (entry && !dax_is_conflict(entry))
dax_wake_entry(xas, entry, false);
dax_wake_entry(xas, entry, mode);
}
/*
@ -286,7 +297,7 @@ static void dax_unlock_entry(struct xa_state *xas, void *entry)
old = xas_store(xas, entry);
xas_unlock_irq(xas);
BUG_ON(!dax_is_locked(old));
dax_wake_entry(xas, entry, false);
dax_wake_entry(xas, entry, WAKE_NEXT);
}
/*
@ -524,7 +535,7 @@ static void *grab_mapping_entry(struct xa_state *xas,
dax_disassociate_entry(entry, mapping, false);
xas_store(xas, NULL); /* undo the PMD join */
dax_wake_entry(xas, entry, true);
dax_wake_entry(xas, entry, WAKE_ALL);
mapping->nrpages -= PG_PMD_NR;
entry = NULL;
xas_set(xas, index);
@ -622,7 +633,7 @@ struct page *dax_layout_busy_page_range(struct address_space *mapping,
entry = get_unlocked_entry(&xas, 0);
if (entry)
page = dax_busy_page(entry);
put_unlocked_entry(&xas, entry);
put_unlocked_entry(&xas, entry, WAKE_NEXT);
if (page)
break;
if (++scanned % XA_CHECK_SCHED)
@ -664,7 +675,7 @@ static int __dax_invalidate_entry(struct address_space *mapping,
mapping->nrpages -= 1UL << dax_entry_order(entry);
ret = 1;
out:
put_unlocked_entry(&xas, entry);
put_unlocked_entry(&xas, entry, WAKE_ALL);
xas_unlock_irq(&xas);
return ret;
}
@ -937,13 +948,13 @@ static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev,
xas_lock_irq(xas);
xas_store(xas, entry);
xas_clear_mark(xas, PAGECACHE_TAG_DIRTY);
dax_wake_entry(xas, entry, false);
dax_wake_entry(xas, entry, WAKE_NEXT);
trace_dax_writeback_one(mapping->host, index, count);
return ret;
put_unlocked:
put_unlocked_entry(xas, entry);
put_unlocked_entry(xas, entry, WAKE_NEXT);
return ret;
}
@ -1684,7 +1695,7 @@ dax_insert_pfn_mkwrite(struct vm_fault *vmf, pfn_t pfn, unsigned int order)
/* Did we race with someone splitting entry or so? */
if (!entry || dax_is_conflict(entry) ||
(order == 0 && !dax_is_pte_entry(entry))) {
put_unlocked_entry(&xas, entry);
put_unlocked_entry(&xas, entry, WAKE_NEXT);
xas_unlock_irq(&xas);
trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf,
VM_FAULT_NOPAGE);