[PATCH v7 01/14] dax: store pfns in the radix

Dan Williams
2018-03-21T23:06:29Z

In preparation for examining the busy state of dax pages in the truncate
path, switch from sectors to pfns in the radix.

Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/dax/super.c | 15 +++++++--
fs/dax.c | 83 +++++++++++++++++++--------------------------------
2 files changed, 43 insertions(+), 55 deletions(-)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index ecdc292aa4e4..2b2332b605e4 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -124,10 +124,19 @@ int __bdev_dax_supported(struct super_block *sb, int blocksize)
return len < 0 ? len : -EIO;
}

- if ((IS_ENABLED(CONFIG_FS_DAX_LIMITED) && pfn_t_special(pfn))
- || pfn_t_devmap(pfn))
+ if (IS_ENABLED(CONFIG_FS_DAX_LIMITED) && pfn_t_special(pfn)) {
+ /*
+ * An arch that has enabled the pmem api should also
+ * have its drivers support pfn_t_devmap()
+ *
+ * This is a developer warning and should not trigger in
+ * production. dax_flush() will crash since it depends
+ * on being able to do (page_address(pfn_to_page())).
+ */
+ WARN_ON(IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API));
+ } else if (pfn_t_devmap(pfn)) {
/* pass */;
- else {
+ } else {
pr_debug("VFS (%s): error: dax support not enabled\n",
sb->s_id);
return -EOPNOTSUPP;
diff --git a/fs/dax.c b/fs/dax.c
index 0276df90e86c..b646a46e4d12 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -73,16 +73,15 @@ fs_initcall(init_dax_wait_table);
#define RADIX_DAX_ZERO_PAGE (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 2))
#define RADIX_DAX_EMPTY (1 << (RADIX_TREE_EXCEPTIONAL_SHIFT + 3))

-static unsigned long dax_radix_sector(void *entry)
+static unsigned long dax_radix_pfn(void *entry)
{
return (unsigned long)entry >> RADIX_DAX_SHIFT;
}

-static void *dax_radix_locked_entry(sector_t sector, unsigned long flags)
+static void *dax_radix_locked_entry(unsigned long pfn, unsigned long flags)
{
return (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY | flags |
- ((unsigned long)sector << RADIX_DAX_SHIFT) |
- RADIX_DAX_ENTRY_LOCK);
+ (pfn << RADIX_DAX_SHIFT) | RADIX_DAX_ENTRY_LOCK);
}

static unsigned int dax_radix_order(void *entry)
@@ -526,12 +525,13 @@ static int copy_user_dax(struct block_device *bdev, struct dax_device *dax_dev,
*/
static void *dax_insert_mapping_entry(struct address_space *mapping,
struct vm_fault *vmf,
- void *entry, sector_t sector,
+ void *entry, pfn_t pfn_t,
unsigned long flags, bool dirty)
{
struct radix_tree_root *page_tree = &mapping->page_tree;
- void *new_entry;
+ unsigned long pfn = pfn_t_to_pfn(pfn_t);
pgoff_t index = vmf->pgoff;
+ void *new_entry;

if (dirty)
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
@@ -546,7 +546,7 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
}

spin_lock_irq(&mapping->tree_lock);
- new_entry = dax_radix_locked_entry(sector, flags);
+ new_entry = dax_radix_locked_entry(pfn, flags);

if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
/*
@@ -657,17 +657,14 @@ static void dax_mapping_entry_mkclean(struct address_space *mapping,
i_mmap_unlock_read(mapping);
}

-static int dax_writeback_one(struct block_device *bdev,
- struct dax_device *dax_dev, struct address_space *mapping,
- pgoff_t index, void *entry)
+static int dax_writeback_one(struct dax_device *dax_dev,
+ struct address_space *mapping, pgoff_t index, void *entry)
{
struct radix_tree_root *page_tree = &mapping->page_tree;
- void *entry2, **slot, *kaddr;
- long ret = 0, id;
- sector_t sector;
- pgoff_t pgoff;
+ void *entry2, **slot;
+ unsigned long pfn;
+ long ret = 0;
size_t size;
- pfn_t pfn;

/*
* A page got tagged dirty in DAX mapping? Something is seriously
@@ -683,10 +680,10 @@ static int dax_writeback_one(struct block_device *bdev,
goto put_unlocked;
/*
* Entry got reallocated elsewhere? No need to writeback. We have to
- * compare sectors as we must not bail out due to difference in lockbit
+ * compare pfns as we must not bail out due to difference in lockbit
* or entry type.
*/
- if (dax_radix_sector(entry2) != dax_radix_sector(entry))
+ if (dax_radix_pfn(entry2) != dax_radix_pfn(entry))
goto put_unlocked;
if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
dax_is_zero_entry(entry))) {
@@ -712,33 +709,15 @@ static int dax_writeback_one(struct block_device *bdev,
/*
* Even if dax_writeback_mapping_range() was given a wbc->range_start
* in the middle of a PMD, the 'index' we are given will be aligned to
- * the start index of the PMD, as will the sector we pull from
- * 'entry'. This allows us to flush for PMD_SIZE and not have to
- * worry about partial PMD writebacks.
+ * the start index of the PMD, as will the pfn we pull from 'entry'.
+ * This allows us to flush for PMD_SIZE and not have to worry about
+ * partial PMD writebacks.
*/
- sector = dax_radix_sector(entry);
+ pfn = dax_radix_pfn(entry);
size = PAGE_SIZE << dax_radix_order(entry);

- id = dax_read_lock();
- ret = bdev_dax_pgoff(bdev, sector, size, &pgoff);
- if (ret)
- goto dax_unlock;
-
- /*
- * dax_direct_access() may sleep, so cannot hold tree_lock over
- * its invocation.
- */
- ret = dax_direct_access(dax_dev, pgoff, size / PAGE_SIZE, &kaddr, &pfn);
- if (ret < 0)
- goto dax_unlock;
-
- if (WARN_ON_ONCE(ret < size / PAGE_SIZE)) {
- ret = -EIO;
- goto dax_unlock;
- }
-
- dax_mapping_entry_mkclean(mapping, index, pfn_t_to_pfn(pfn));
- dax_flush(dax_dev, kaddr, size);
+ dax_mapping_entry_mkclean(mapping, index, pfn);
+ dax_flush(dax_dev, page_address(pfn_to_page(pfn)), size);
/*
* After we have flushed the cache, we can clear the dirty tag. There
* cannot be new dirty data in the pfn after the flush has completed as
@@ -749,8 +728,6 @@ static int dax_writeback_one(struct block_device *bdev,
radix_tree_tag_clear(page_tree, index, PAGECACHE_TAG_DIRTY);
spin_unlock_irq(&mapping->tree_lock);
trace_dax_writeback_one(mapping->host, index, size >> PAGE_SHIFT);
- dax_unlock:
- dax_read_unlock(id);
put_locked_mapping_entry(mapping, index);
return ret;

@@ -808,8 +785,8 @@ int dax_writeback_mapping_range(struct address_space *mapping,
break;
}

- ret = dax_writeback_one(bdev, dax_dev, mapping,
- indices[i], pvec.pages[i]);
+ ret = dax_writeback_one(dax_dev, mapping, indices[i],
+ pvec.pages[i]);
if (ret < 0) {
mapping_set_error(mapping, ret);
goto out;
@@ -877,6 +854,7 @@ static int dax_load_hole(struct address_space *mapping, void *entry,
int ret = VM_FAULT_NOPAGE;
struct page *zero_page;
void *entry2;
+ pfn_t pfn;

zero_page = ZERO_PAGE(0);
if (unlikely(!zero_page)) {
@@ -884,14 +862,15 @@ static int dax_load_hole(struct address_space *mapping, void *entry,
goto out;
}

- entry2 = dax_insert_mapping_entry(mapping, vmf, entry, 0,
+ pfn = page_to_pfn_t(zero_page);
+ entry2 = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
RADIX_DAX_ZERO_PAGE, false);
if (IS_ERR(entry2)) {
ret = VM_FAULT_SIGBUS;
goto out;
}

- vm_insert_mixed(vmf->vma, vaddr, page_to_pfn_t(zero_page));
+ vm_insert_mixed(vmf->vma, vaddr, pfn);
out:
trace_dax_load_hole(inode, vmf, ret);
return ret;
@@ -1200,8 +1179,7 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
if (error < 0)
goto error_finish_iomap;

- entry = dax_insert_mapping_entry(mapping, vmf, entry,
- dax_iomap_sector(&iomap, pos),
+ entry = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
0, write && !sync);
if (IS_ERR(entry)) {
error = PTR_ERR(entry);
@@ -1280,13 +1258,15 @@ static int dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap,
void *ret = NULL;
spinlock_t *ptl;
pmd_t pmd_entry;
+ pfn_t pfn;

zero_page = mm_get_huge_zero_page(vmf->vma->vm_mm);

if (unlikely(!zero_page))
goto fallback;

- ret = dax_insert_mapping_entry(mapping, vmf, entry, 0,
+ pfn = page_to_pfn_t(zero_page);
+ ret = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
RADIX_DAX_PMD | RADIX_DAX_ZERO_PAGE, false);
if (IS_ERR(ret))
goto fallback;
@@ -1409,8 +1389,7 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
if (error < 0)
goto finish_iomap;

- entry = dax_insert_mapping_entry(mapping, vmf, entry,
- dax_iomap_sector(&iomap, pos),
+ entry = dax_insert_mapping_entry(mapping, vmf, entry, pfn,
RADIX_DAX_PMD, write && !sync);
if (IS_ERR(entry))
goto finish_iomap;