blk_queue_exit(bdev->bd_queue);
}
+static int dax_is_pmd_entry(void *entry)
+{
+ return (unsigned long)entry & RADIX_DAX_PMD;
+}
+
+static int dax_is_pte_entry(void *entry)
+{
+ return !((unsigned long)entry & RADIX_DAX_PMD);
+}
+
+static int dax_is_zero_entry(void *entry)
+{
+ return (unsigned long)entry & RADIX_DAX_HZP;
+}
+
+static int dax_is_empty_entry(void *entry)
+{
+ return (unsigned long)entry & RADIX_DAX_EMPTY;
+}
+
struct page *read_dax_sector(struct block_device *bdev, sector_t n)
{
struct page *page = alloc_pages(GFP_KERNEL, 0);
* queue to the start of that PMD. This ensures that all offsets in
* the range covered by the PMD map to the same bit lock.
*/
- if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+ if (dax_is_pmd_entry(entry))
index &= ~((1UL << (PMD_SHIFT - PAGE_SHIFT)) - 1);
key->mapping = mapping;
* radix tree entry locked. If the radix tree doesn't contain given index,
* create empty exceptional entry for the index and return with it locked.
*
+ * When requesting an entry with size RADIX_DAX_PMD, grab_mapping_entry() will
+ * either return that locked entry or will return an error. This error will
+ * happen if there are any 4k entries (either zero pages or DAX entries)
+ * within the 2MiB range that we are requesting.
+ *
+ * We always favor 4k entries over 2MiB entries. There isn't a flow where we
+ * evict 4k entries in order to 'upgrade' them to a 2MiB entry. A 2MiB
+ * insertion will fail if it finds any 4k entries already in the tree, and a
+ * 4k insertion will cause an existing 2MiB entry to be unmapped and
+ * downgraded to 4k entries. This happens for both 2MiB huge zero pages as
+ * well as 2MiB empty entries.
+ *
+ * The exception to this downgrade path is for 2MiB DAX PMD entries that have
+ * real storage backing them. We will leave these real 2MiB DAX entries in
+ * the tree, and PTE writes will simply dirty the entire 2MiB DAX entry.
+ *
* Note: Unlike filemap_fault() we don't honor FAULT_FLAG_RETRY flags. For
* persistent memory the benefit is doubtful. We can add that later if we can
* show it helps.
*/
-static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index)
+static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
+ unsigned long size_flag)
{
+ bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
void *entry, **slot;
restart:
spin_lock_irq(&mapping->tree_lock);
entry = get_unlocked_mapping_entry(mapping, index, &slot);
+
+ if (entry) {
+ if (size_flag & RADIX_DAX_PMD) {
+ if (!radix_tree_exceptional_entry(entry) ||
+ dax_is_pte_entry(entry)) {
+ put_unlocked_mapping_entry(mapping, index,
+ entry);
+ entry = ERR_PTR(-EEXIST);
+ goto out_unlock;
+ }
+ } else { /* trying to grab a PTE entry */
+ if (radix_tree_exceptional_entry(entry) &&
+ dax_is_pmd_entry(entry) &&
+ (dax_is_zero_entry(entry) ||
+ dax_is_empty_entry(entry))) {
+ pmd_downgrade = true;
+ }
+ }
+ }
+
/* No entry for given index? Make sure radix tree is big enough. */
- if (!entry) {
+ if (!entry || pmd_downgrade) {
int err;
+ if (pmd_downgrade) {
+ /*
+ * Make sure 'entry' remains valid while we drop
+ * mapping->tree_lock.
+ */
+ entry = lock_slot(mapping, slot);
+ }
+
spin_unlock_irq(&mapping->tree_lock);
err = radix_tree_preload(
mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
- if (err)
+ if (err) {
+ if (pmd_downgrade)
+ put_locked_mapping_entry(mapping, index, entry);
return ERR_PTR(err);
- entry = (void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
- RADIX_DAX_ENTRY_LOCK);
+ }
+
+ /*
+ * Besides huge zero pages the only other thing that gets
+ * downgraded are empty entries which don't need to be
+ * unmapped.
+ */
+ if (pmd_downgrade && dax_is_zero_entry(entry))
+ unmap_mapping_range(mapping,
+ (index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
+
spin_lock_irq(&mapping->tree_lock);
- err = radix_tree_insert(&mapping->page_tree, index, entry);
+
+ if (pmd_downgrade) {
+ radix_tree_delete(&mapping->page_tree, index);
+ mapping->nrexceptional--;
+ dax_wake_mapping_entry_waiter(mapping, index, entry,
+ true);
+ }
+
+ entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);
+
+ err = __radix_tree_insert(&mapping->page_tree, index,
+ dax_radix_order(entry), entry);
radix_tree_preload_end();
if (err) {
spin_unlock_irq(&mapping->tree_lock);
- /* Someone already created the entry? */
- if (err == -EEXIST)
+ /*
+ * Someone already created the entry? This is a
+ * normal failure when inserting PMDs in a range
+ * that already contains PTEs. In that case we want
+ * to return -EEXIST immediately.
+ */
+ if (err == -EEXIST && !(size_flag & RADIX_DAX_PMD))
goto restart;
+ /*
+ * Our insertion of a DAX PMD entry failed, most
+ * likely because it collided with a PTE sized entry
+ * at a different index in the PMD range. We haven't
+ * inserted anything into the radix tree and have no
+ * waiters to wake.
+ */
return ERR_PTR(err);
}
/* Good, we have inserted empty locked entry into the tree. */
return page;
}
entry = lock_slot(mapping, slot);
+ out_unlock:
spin_unlock_irq(&mapping->tree_lock);
return entry;
}
/*
* We do not necessarily hold the mapping->tree_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, though, because all we really need to do is to
- * find the correct waitqueue where tasks might be sleeping waiting for that
- * old 'entry' and wake them.
+ * 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.
*/
void dax_wake_mapping_entry_waiter(struct address_space *mapping,
pgoff_t index, void *entry, bool wake_all)
return 0;
}
-#define DAX_PMD_INDEX(page_index) (page_index & (PMD_MASK >> PAGE_SHIFT))
-
+/*
+ * By this point grab_mapping_entry() has ensured that we have a locked entry
+ * of the appropriate size so we don't have to worry about downgrading PMDs to
+ * PTEs. If we happen to be trying to insert a PTE and there is a PMD
+ * already in the tree, we will skip the insertion and just dirty the PMD as
+ * appropriate.
+ */
static void *dax_insert_mapping_entry(struct address_space *mapping,
struct vm_fault *vmf,
- void *entry, sector_t sector)
+ void *entry, sector_t sector,
+ unsigned long flags)
{
struct radix_tree_root *page_tree = &mapping->page_tree;
int error = 0;
error = radix_tree_preload(vmf->gfp_mask & ~__GFP_HIGHMEM);
if (error)
return ERR_PTR(error);
+ } else if (dax_is_zero_entry(entry) && !(flags & RADIX_DAX_HZP)) {
+ /* replacing huge zero page with PMD block mapping */
+ unmap_mapping_range(mapping,
+ (vmf->pgoff << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
}
spin_lock_irq(&mapping->tree_lock);
- new_entry = (void *)((unsigned long)RADIX_DAX_ENTRY(sector, false) |
- RADIX_DAX_ENTRY_LOCK);
+ new_entry = dax_radix_locked_entry(sector, flags);
+
if (hole_fill) {
__delete_from_page_cache(entry, NULL);
/* Drop pagecache reference */
put_page(entry);
- error = radix_tree_insert(page_tree, index, new_entry);
+ error = __radix_tree_insert(page_tree, index,
+ dax_radix_order(new_entry), new_entry);
if (error) {
new_entry = ERR_PTR(error);
goto unlock;
}
mapping->nrexceptional++;
- } else {
+ } else if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
+ /*
+ * Only swap our new entry into the radix tree if the current
+ * entry is a zero page or an empty entry. If a normal PTE or
+ * PMD entry is already in the tree, we leave it alone. This
+ * means that if we are trying to insert a PTE and the
+ * existing entry is a PMD, we will just leave the PMD in the
+ * tree and dirty it if necessary.
+ */
void **slot;
void *ret;
struct address_space *mapping, pgoff_t index, void *entry)
{
struct radix_tree_root *page_tree = &mapping->page_tree;
- int type = RADIX_DAX_TYPE(entry);
struct radix_tree_node *node;
struct blk_dax_ctl dax;
void **slot;
if (!radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))
goto unlock;
- if (WARN_ON_ONCE(type != RADIX_DAX_PTE && type != RADIX_DAX_PMD)) {
+ if (WARN_ON_ONCE(dax_is_empty_entry(entry) ||
+ dax_is_zero_entry(entry))) {
ret = -EIO;
goto unlock;
}
- dax.sector = RADIX_DAX_SECTOR(entry);
- dax.size = (type == RADIX_DAX_PMD ? PMD_SIZE : PAGE_SIZE);
+ /*
+ * 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.
+ */
+ dax.sector = dax_radix_sector(entry);
+ dax.size = PAGE_SIZE << dax_radix_order(entry);
spin_unlock_irq(&mapping->tree_lock);
/*
struct block_device *bdev, struct writeback_control *wbc)
{
struct inode *inode = mapping->host;
- pgoff_t start_index, end_index, pmd_index;
+ pgoff_t start_index, end_index;
pgoff_t indices[PAGEVEC_SIZE];
struct pagevec pvec;
bool done = false;
int i, ret = 0;
- void *entry;
if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT))
return -EIO;
start_index = wbc->range_start >> PAGE_SHIFT;
end_index = wbc->range_end >> PAGE_SHIFT;
- pmd_index = DAX_PMD_INDEX(start_index);
-
- rcu_read_lock();
- entry = radix_tree_lookup(&mapping->page_tree, pmd_index);
- rcu_read_unlock();
-
- /* see if the start of our range is covered by a PMD entry */
- if (entry && RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
- start_index = pmd_index;
tag_pages_for_writeback(mapping, start_index, end_index);
return PTR_ERR(dax.addr);
dax_unmap_atomic(bdev, &dax);
- ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector);
+ ret = dax_insert_mapping_entry(mapping, vmf, entry, dax.sector, 0);
if (IS_ERR(ret))
return PTR_ERR(ret);
*entryp = ret;
bh.b_bdev = inode->i_sb->s_bdev;
bh.b_size = PAGE_SIZE;
- entry = grab_mapping_entry(mapping, vmf->pgoff);
+ entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
if (IS_ERR(entry)) {
error = PTR_ERR(entry);
goto out;
if (pos >= i_size_read(inode))
return VM_FAULT_SIGBUS;
- entry = grab_mapping_entry(mapping, vmf->pgoff);
+ entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
if (IS_ERR(entry)) {
error = PTR_ERR(entry);
goto out;
return VM_FAULT_NOPAGE | major;
}
EXPORT_SYMBOL_GPL(dax_iomap_fault);
+
+#ifdef CONFIG_FS_DAX_PMD
+/*
+ * The 'colour' (ie low bits) within a PMD of a page offset. This comes up
+ * more often than one might expect in the below functions.
+ */
+#define PG_PMD_COLOUR ((PMD_SIZE >> PAGE_SHIFT) - 1)
+
+static int dax_pmd_insert_mapping(struct vm_area_struct *vma, pmd_t *pmd,
+ struct vm_fault *vmf, unsigned long address,
+ struct iomap *iomap, loff_t pos, bool write, void **entryp)
+{
+ struct address_space *mapping = vma->vm_file->f_mapping;
+ struct block_device *bdev = iomap->bdev;
+ struct blk_dax_ctl dax = {
+ .sector = dax_iomap_sector(iomap, pos),
+ .size = PMD_SIZE,
+ };
+ long length = dax_map_atomic(bdev, &dax);
+ void *ret;
+
+ if (length < 0) /* dax_map_atomic() failed */
+ return VM_FAULT_FALLBACK;
+ if (length < PMD_SIZE)
+ goto unmap_fallback;
+ if (pfn_t_to_pfn(dax.pfn) & PG_PMD_COLOUR)
+ goto unmap_fallback;
+ if (!pfn_t_devmap(dax.pfn))
+ goto unmap_fallback;
+
+ dax_unmap_atomic(bdev, &dax);
+
+ ret = dax_insert_mapping_entry(mapping, vmf, *entryp, dax.sector,
+ RADIX_DAX_PMD);
+ if (IS_ERR(ret))
+ return VM_FAULT_FALLBACK;
+ *entryp = ret;
+
+ return vmf_insert_pfn_pmd(vma, address, pmd, dax.pfn, write);
+
+ unmap_fallback:
+ dax_unmap_atomic(bdev, &dax);
+ return VM_FAULT_FALLBACK;
+}
+
+static int dax_pmd_load_hole(struct vm_area_struct *vma, pmd_t *pmd,
+ struct vm_fault *vmf, unsigned long address,
+ struct iomap *iomap, void **entryp)
+{
+ struct address_space *mapping = vma->vm_file->f_mapping;
+ unsigned long pmd_addr = address & PMD_MASK;
+ struct page *zero_page;
+ spinlock_t *ptl;
+ pmd_t pmd_entry;
+ void *ret;
+
+ zero_page = mm_get_huge_zero_page(vma->vm_mm);
+
+ if (unlikely(!zero_page))
+ return VM_FAULT_FALLBACK;
+
+ ret = dax_insert_mapping_entry(mapping, vmf, *entryp, 0,
+ RADIX_DAX_PMD | RADIX_DAX_HZP);
+ if (IS_ERR(ret))
+ return VM_FAULT_FALLBACK;
+ *entryp = ret;
+
+ ptl = pmd_lock(vma->vm_mm, pmd);
+ if (!pmd_none(*pmd)) {
+ spin_unlock(ptl);
+ return VM_FAULT_FALLBACK;
+ }
+
+ pmd_entry = mk_pmd(zero_page, vma->vm_page_prot);
+ pmd_entry = pmd_mkhuge(pmd_entry);
+ set_pmd_at(vma->vm_mm, pmd_addr, pmd, pmd_entry);
+ spin_unlock(ptl);
+ return VM_FAULT_NOPAGE;
+}
+
+int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
+ pmd_t *pmd, unsigned int flags, struct iomap_ops *ops)
+{
+ struct address_space *mapping = vma->vm_file->f_mapping;
+ unsigned long pmd_addr = address & PMD_MASK;
+ bool write = flags & FAULT_FLAG_WRITE;
+ unsigned int iomap_flags = write ? IOMAP_WRITE : 0;
+ struct inode *inode = mapping->host;
+ int result = VM_FAULT_FALLBACK;
+ struct iomap iomap = { 0 };
+ pgoff_t max_pgoff, pgoff;
+ struct vm_fault vmf;
+ void *entry;
+ loff_t pos;
+ int error;
+
+ /* Fall back to PTEs if we're going to COW */
+ if (write && !(vma->vm_flags & VM_SHARED))
+ goto fallback;
+
+ /* If the PMD would extend outside the VMA */
+ if (pmd_addr < vma->vm_start)
+ goto fallback;
+ if ((pmd_addr + PMD_SIZE) > vma->vm_end)
+ goto fallback;
+
+ /*
+ * Check whether offset isn't beyond end of file now. Caller is
+ * supposed to hold locks serializing us with truncate / punch hole so
+ * this is a reliable test.
+ */
+ pgoff = linear_page_index(vma, pmd_addr);
+ max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;
+
+ if (pgoff > max_pgoff)
+ return VM_FAULT_SIGBUS;
+
+ /* If the PMD would extend beyond the file size */
+ if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
+ goto fallback;
+
+ /*
+ * grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
+ * PMD or a HZP entry. If it can't (because a 4k page is already in
+ * the tree, for instance), it will return -EEXIST and we just fall
+ * back to 4k entries.
+ */
+ entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
+ if (IS_ERR(entry))
+ goto fallback;
+
+ /*
+ * Note that we don't use iomap_apply here. We aren't doing I/O, only
+ * setting up a mapping, so really we're using iomap_begin() as a way
+ * to look up our filesystem block.
+ */
+ pos = (loff_t)pgoff << PAGE_SHIFT;
+ error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
+ if (error)
+ goto unlock_entry;
+ if (iomap.offset + iomap.length < pos + PMD_SIZE)
+ goto finish_iomap;
+
+ vmf.pgoff = pgoff;
+ vmf.flags = flags;
+ vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
+
+ switch (iomap.type) {
+ case IOMAP_MAPPED:
+ result = dax_pmd_insert_mapping(vma, pmd, &vmf, address,
+ &iomap, pos, write, &entry);
+ break;
+ case IOMAP_UNWRITTEN:
+ case IOMAP_HOLE:
+ if (WARN_ON_ONCE(write))
+ goto finish_iomap;
+ result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
+ &entry);
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ break;
+ }
+
+ finish_iomap:
+ if (ops->iomap_end) {
+ if (result == VM_FAULT_FALLBACK) {
+ ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
+ &iomap);
+ } else {
+ error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
+ iomap_flags, &iomap);
+ if (error)
+ result = VM_FAULT_FALLBACK;
+ }
+ }
+ unlock_entry:
+ put_locked_mapping_entry(mapping, pgoff, entry);
+ fallback:
+ if (result == VM_FAULT_FALLBACK) {
+ split_huge_pmd(vma, pmd, address);
+ count_vm_event(THP_FAULT_FALLBACK);
+ }
+ return result;
+}
+EXPORT_SYMBOL_GPL(dax_iomap_pmd_fault);
+#endif /* CONFIG_FS_DAX_PMD */
#endif /* CONFIG_FS_IOMAP */
projects / linux-beck.git / commitdiff