From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
This time, we want to convert get_unlocked_mapping_entry() to use the
XArray. That has a ripple effect, causing us to change the waitqueues
to hash on the address of the xarray rather than the address of the
mapping (functionally equivalent), and create a lot of on-the-stack
xa_state which are only used as a container for passing the xarray and
the index down to deeper function calls.
Also rename dax_wake_mapping_entry_waiter() to dax_wake_entry().
Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
---
fs/dax.c | 80 +++++++++++++++++++++++++++++-----------------------------------
1 file changed, 36 insertions(+), 44 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index d2007a17d257..ad984dece12e 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -120,7 +120,7 @@ static int dax_is_empty_entry(void *entry)
* DAX radix tree locking
*/
struct exceptional_entry_key {
- struct address_space *mapping;
+ struct xarray *xa;
pgoff_t entry_start;
};
@@ -129,9 +129,10 @@ struct wait_exceptional_entry_queue {
struct exceptional_entry_key key;
};
-static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
- pgoff_t index, void *entry, struct exceptional_entry_key *key)
+static wait_queue_head_t *dax_entry_waitqueue(struct xa_state *xas,
+ void *entry, struct exceptional_entry_key *key)
{
+ unsigned long index = xas->xa_index;
unsigned long hash;
/*
@@ -142,10 +143,10 @@ static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
if (dax_is_pmd_entry(entry))
index &= ~PG_PMD_COLOUR;
- key->mapping = mapping;
+ key->xa = xas->xa;
key->entry_start = index;
- hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
+ hash = hash_long((unsigned long)xas->xa ^ index, DAX_WAIT_TABLE_BITS);
return wait_table + hash;
}
@@ -156,26 +157,23 @@ static int wake_exceptional_entry_func(wait_queue_entry_t *wait, unsigned int mo
struct wait_exceptional_entry_queue *ewait =
container_of(wait, struct wait_exceptional_entry_queue, wait);
- if (key->mapping != ewait->key.mapping ||
+ if (key->xa != ewait->key.xa ||
key->entry_start != ewait->key.entry_start)
return 0;
return autoremove_wake_function(wait, mode, sync, NULL);
}
/*
- * We do not necessarily hold the mapping xa_lock when we call this
- * function so it is possible that 'entry' is no longer a valid item in the
- * radix tree. This is okay because all we really need to do is to find the
- * correct waitqueue where tasks might be waiting for that old 'entry' and
- * wake them.
+ * @entry may no longer be the entry at the index in the array. The
+ * important information it's conveying is whether the entry at this
+ * index *used* to be a PMD entry..
*/
-static void dax_wake_mapping_entry_waiter(struct address_space *mapping,
- pgoff_t index, void *entry, bool wake_all)
+static void dax_wake_entry(struct xa_state *xas, void *entry, bool wake_all)
{
struct exceptional_entry_key key;
wait_queue_head_t *wq;
- wq = dax_entry_waitqueue(mapping, index, entry, &key);
+ wq = dax_entry_waitqueue(xas, entry, &key);
/*
* Checking for locked entry and prepare_to_wait_exclusive() happens
@@ -207,10 +205,9 @@ static inline void *lock_slot(struct xa_state *xas)
*
* The function must be called with mapping xa_lock held.
*/
-static void *get_unlocked_mapping_entry(struct address_space *mapping,
- pgoff_t index, void ***slotp)
+static void *get_unlocked_mapping_entry(struct xa_state *xas)
{
- void *entry, **slot;
+ void *entry;
struct wait_exceptional_entry_queue ewait;
wait_queue_head_t *wq;
@@ -218,22 +215,19 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
ewait.wait.func = wake_exceptional_entry_func;
for (;;) {
- entry = __radix_tree_lookup(&mapping->pages, index, NULL,
- &slot);
- if (!entry ||
- WARN_ON_ONCE(!xa_is_value(entry)) || !dax_locked(entry)) {
- if (slotp)
- *slotp = slot;
+ entry = xas_load(xas);
+ if (!entry || WARN_ON_ONCE(!xa_is_value(entry)) ||
+ !dax_locked(entry))
return entry;
- }
- wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
+ wq = dax_entry_waitqueue(xas, entry, &ewait.key);
prepare_to_wait_exclusive(wq, &ewait.wait,
TASK_UNINTERRUPTIBLE);
- xa_unlock_irq(&mapping->pages);
+ xas_pause(xas);
+ xas_unlock_irq(xas);
schedule();
finish_wait(wq, &ewait.wait);
- xa_lock_irq(&mapping->pages);
+ xas_lock_irq(xas);
}
}
@@ -253,7 +247,7 @@ static void dax_unlock_mapping_entry(struct address_space *mapping,
xas_store(&xas, entry);
/* Safe to not call xas_pause here -- we don't touch the array after */
xas_unlock_irq(&xas);
- dax_wake_mapping_entry_waiter(mapping, index, entry, false);
+ dax_wake_entry(&xas, entry, false);
}
static void put_locked_mapping_entry(struct address_space *mapping,
@@ -266,14 +260,13 @@ static void put_locked_mapping_entry(struct address_space *mapping,
* Called when we are done with radix tree entry we looked up via
* get_unlocked_mapping_entry() and which we didn't lock in the end.
*/
-static void put_unlocked_mapping_entry(struct address_space *mapping,
- pgoff_t index, void *entry)
+static void put_unlocked_mapping_entry(struct xa_state *xas, void *entry)
{
if (!entry)
return;
/* We have to wake up next waiter for the radix tree entry lock */
- dax_wake_mapping_entry_waiter(mapping, index, entry, false);
+ dax_wake_entry(xas, entry, false);
}
/*
@@ -310,7 +303,7 @@ static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
restart:
xa_lock_irq(&mapping->pages);
- entry = get_unlocked_mapping_entry(mapping, index, &slot);
+ entry = get_unlocked_mapping_entry(&xas);
if (WARN_ON_ONCE(entry && !xa_is_value(entry))) {
entry = ERR_PTR(-EIO);
@@ -320,8 +313,7 @@ static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
if (entry) {
if (size_flag & DAX_PMD) {
if (dax_is_pte_entry(entry)) {
- put_unlocked_mapping_entry(mapping, index,
- entry);
+ put_unlocked_mapping_entry(&xas, entry);
entry = ERR_PTR(-EEXIST);
goto out_unlock;
}
@@ -384,8 +376,7 @@ static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
if (pmd_downgrade) {
radix_tree_delete(&mapping->pages, index);
mapping->nrexceptional--;
- dax_wake_mapping_entry_waiter(mapping, index, entry,
- true);
+ dax_wake_entry(&xas, entry, true);
}
entry = dax_radix_locked_entry(0, size_flag | DAX_EMPTY);
@@ -419,12 +410,13 @@ static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
static int __dax_invalidate_mapping_entry(struct address_space *mapping,
pgoff_t index, bool trunc)
{
+ XA_STATE(xas, &mapping->pages, index);
int ret = 0;
void *entry;
struct radix_tree_root *pages = &mapping->pages;
xa_lock_irq(&mapping->pages);
- entry = get_unlocked_mapping_entry(mapping, index, NULL);
+ entry = get_unlocked_mapping_entry(&xas);
if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))
goto out;
if (!trunc &&
@@ -435,7 +427,7 @@ static int __dax_invalidate_mapping_entry(struct address_space *mapping,
mapping->nrexceptional--;
ret = 1;
out:
- put_unlocked_mapping_entry(mapping, index, entry);
+ put_unlocked_mapping_entry(&xas, entry);
xa_unlock_irq(&mapping->pages);
return ret;
}
@@ -643,7 +635,7 @@ static int dax_writeback_one(struct block_device *bdev,
{
struct radix_tree_root *pages = &mapping->pages;
XA_STATE(xas, pages, index);
- void *entry2, **slot, *kaddr;
+ void *entry2, *kaddr;
long ret = 0, id;
sector_t sector;
pgoff_t pgoff;
@@ -658,7 +650,7 @@ static int dax_writeback_one(struct block_device *bdev,
return -EIO;
xa_lock_irq(&mapping->pages);
- entry2 = get_unlocked_mapping_entry(mapping, index, &slot);
+ entry2 = get_unlocked_mapping_entry(&xas);
/* Entry got punched out / reallocated? */
if (!entry2 || WARN_ON_ONCE(!xa_is_value(entry2)))
goto put_unlocked;
@@ -736,7 +728,7 @@ static int dax_writeback_one(struct block_device *bdev,
return ret;
put_unlocked:
- put_unlocked_mapping_entry(mapping, index, entry2);
+ put_unlocked_mapping_entry(&xas, entry2);
xa_unlock_irq(&mapping->pages);
return ret;
}
@@ -1506,16 +1498,16 @@ static int dax_insert_pfn_mkwrite(struct vm_fault *vmf,
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
pgoff_t index = vmf->pgoff;
XA_STATE(xas, &mapping->pages, index);
- void *entry, **slot;
+ void *entry;
int vmf_ret, error;
xa_lock_irq(&mapping->pages);
- entry = get_unlocked_mapping_entry(mapping, index, &slot);
+ entry = get_unlocked_mapping_entry(&xas);
/* Did we race with someone splitting entry or so? */
if (!entry ||
(pe_size == PE_SIZE_PTE && !dax_is_pte_entry(entry)) ||
(pe_size == PE_SIZE_PMD && !dax_is_pmd_entry(entry))) {
- put_unlocked_mapping_entry(mapping, index, entry);
+ put_unlocked_mapping_entry(&xas, entry);
xa_unlock_irq(&mapping->pages);
trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf,
VM_FAULT_NOPAGE);
--
2.15.0
--
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