1 files changed, 240 insertions, 12 deletions

diff --git a/fs/dax.c b/fs/dax.c
index 993dc6fe0416..cc025f82ef07 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -31,6 +31,8 @@
 #include <linux/vmstat.h>
 #include <linux/pfn_t.h>
 #include <linux/sizes.h>
+#include <linux/iomap.h>
+#include "internal.h"
 
 /*
  * We use lowest available bit in exceptional entry for locking, other two
@@ -580,14 +582,13 @@ static int dax_load_hole(struct address_space *mapping, void *entry,
         return VM_FAULT_LOCKED;
 }
 
-static int copy_user_bh(struct page *to, struct inode *inode,
-                struct buffer_head *bh, unsigned long vaddr)
+static int copy_user_dax(struct block_device *bdev, sector_t sector, size_t size,
+                struct page *to, unsigned long vaddr)
 {
         struct blk_dax_ctl dax = {
-                .sector = to_sector(bh, inode),
-                .size = bh->b_size,
+                .sector = sector,
+                .size = size,
         };
-        struct block_device *bdev = bh->b_bdev;
         void *vto;
 
         if (dax_map_atomic(bdev, &dax) < 0)
@@ -790,14 +791,13 @@ int dax_writeback_mapping_range(struct address_space *mapping,
 EXPORT_SYMBOL_GPL(dax_writeback_mapping_range);
 
 static int dax_insert_mapping(struct address_space *mapping,
-                        struct buffer_head *bh, void **entryp,
-                        struct vm_area_struct *vma, struct vm_fault *vmf)
+                struct block_device *bdev, sector_t sector, size_t size,
+                void **entryp, struct vm_area_struct *vma, struct vm_fault *vmf)
 {
         unsigned long vaddr = (unsigned long)vmf->virtual_address;
-        struct block_device *bdev = bh->b_bdev;
         struct blk_dax_ctl dax = {
-                .sector = to_sector(bh, mapping->host),
-                .size = bh->b_size,
+                .sector = sector,
+                .size = size,
         };
         void *ret;
         void *entry = *entryp;
@@ -868,7 +868,8 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
         if (vmf->cow_page) {
                 struct page *new_page = vmf->cow_page;
                 if (buffer_written(&bh))
-                        error = copy_user_bh(new_page, inode, &bh, vaddr);
+                        error = copy_user_dax(bh.b_bdev, to_sector(&bh, inode),
+                                        bh.b_size, new_page, vaddr);
                 else
                         clear_user_highpage(new_page, vaddr);
                 if (error)
@@ -898,7 +899,8 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 
         /* Filesystem should not return unwritten buffers to us! */
         WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh));
-        error = dax_insert_mapping(mapping, &bh, &entry, vma, vmf);
+        error = dax_insert_mapping(mapping, bh.b_bdev, to_sector(&bh, inode),
+                        bh.b_size, &entry, vma, vmf);
  unlock_entry:
         put_locked_mapping_entry(mapping, vmf->pgoff, entry);
  out:
@@ -1241,3 +1243,229 @@ int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
         return dax_zero_page_range(inode, from, length, get_block);
 }
 EXPORT_SYMBOL_GPL(dax_truncate_page);
+
+#ifdef CONFIG_FS_IOMAP
+static loff_t
+iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
+                struct iomap *iomap)
+{
+        struct iov_iter *iter = data;
+        loff_t end = pos + length, done = 0;
+        ssize_t ret = 0;
+
+        if (iov_iter_rw(iter) == READ) {
+                end = min(end, i_size_read(inode));
+                if (pos >= end)
+                        return 0;
+
+                if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
+                        return iov_iter_zero(min(length, end - pos), iter);
+        }
+
+        if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
+                return -EIO;
+
+        while (pos < end) {
+                unsigned offset = pos & (PAGE_SIZE - 1);
+                struct blk_dax_ctl dax = { 0 };
+                ssize_t map_len;
+
+                dax.sector = iomap->blkno +
+                        (((pos & PAGE_MASK) - iomap->offset) >> 9);
+                dax.size = (length + offset + PAGE_SIZE - 1) & PAGE_MASK;
+                map_len = dax_map_atomic(iomap->bdev, &dax);
+                if (map_len < 0) {
+                        ret = map_len;
+                        break;
+                }
+
+                dax.addr += offset;
+                map_len -= offset;
+                if (map_len > end - pos)
+                        map_len = end - pos;
+
+                if (iov_iter_rw(iter) == WRITE)
+                        map_len = copy_from_iter_pmem(dax.addr, map_len, iter);
+                else
+                        map_len = copy_to_iter(dax.addr, map_len, iter);
+                dax_unmap_atomic(iomap->bdev, &dax);
+                if (map_len <= 0) {
+                        ret = map_len ? map_len : -EFAULT;
+                        break;
+                }
+
+                pos += map_len;
+                length -= map_len;
+                done += map_len;
+        }
+
+        return done ? done : ret;
+}
+
+/**
+ * iomap_dax_rw - Perform I/O to a DAX file
+ * @iocb:       The control block for this I/O
+ * @iter:       The addresses to do I/O from or to
+ * @ops:        iomap ops passed from the file system
+ *
+ * This function performs read and write operations to directly mapped
+ * persistent memory.  The callers needs to take care of read/write exclusion
+ * and evicting any page cache pages in the region under I/O.
+ */
+ssize_t
+iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
+                struct iomap_ops *ops)
+{
+        struct address_space *mapping = iocb->ki_filp->f_mapping;
+        struct inode *inode = mapping->host;
+        loff_t pos = iocb->ki_pos, ret = 0, done = 0;
+        unsigned flags = 0;
+
+        if (iov_iter_rw(iter) == WRITE)
+                flags |= IOMAP_WRITE;
+
+        /*
+         * Yes, even DAX files can have page cache attached to them:  A zeroed
+         * page is inserted into the pagecache when we have to serve a write
+         * fault on a hole.  It should never be dirtied and can simply be
+         * dropped from the pagecache once we get real data for the page.
+         *
+         * XXX: This is racy against mmap, and there's nothing we can do about
+         * it. We'll eventually need to shift this down even further so that
+         * we can check if we allocated blocks over a hole first.
+         */
+        if (mapping->nrpages) {
+                ret = invalidate_inode_pages2_range(mapping,
+                                pos >> PAGE_SHIFT,
+                                (pos + iov_iter_count(iter) - 1) >> PAGE_SHIFT);
+                WARN_ON_ONCE(ret);
+        }
+
+        while (iov_iter_count(iter)) {
+                ret = iomap_apply(inode, pos, iov_iter_count(iter), flags, ops,
+                                iter, iomap_dax_actor);
+                if (ret <= 0)
+                        break;
+                pos += ret;
+                done += ret;
+        }
+
+        iocb->ki_pos += done;
+        return done ? done : ret;
+}
+EXPORT_SYMBOL_GPL(iomap_dax_rw);
+
+/**
+ * iomap_dax_fault - handle a page fault on a DAX file
+ * @vma: The virtual memory area where the fault occurred
+ * @vmf: The description of the fault
+ * @ops: iomap ops passed from the file system
+ *
+ * When a page fault occurs, filesystems may call this helper in their fault
+ * or mkwrite handler for DAX files. Assumes the caller has done all the
+ * necessary locking for the page fault to proceed successfully.
+ */
+int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
+                        struct iomap_ops *ops)
+{
+        struct address_space *mapping = vma->vm_file->f_mapping;
+        struct inode *inode = mapping->host;
+        unsigned long vaddr = (unsigned long)vmf->virtual_address;
+        loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT;
+        sector_t sector;
+        struct iomap iomap = { 0 };
+        unsigned flags = 0;
+        int error, major = 0;
+        void *entry;
+
+        /*
+         * 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.
+         */
+        if (pos >= i_size_read(inode))
+                return VM_FAULT_SIGBUS;
+
+        entry = grab_mapping_entry(mapping, vmf->pgoff);
+        if (IS_ERR(entry)) {
+                error = PTR_ERR(entry);
+                goto out;
+        }
+
+        if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
+                flags |= IOMAP_WRITE;
+
+        /*
+         * Note that we don't bother to use iomap_apply here: DAX required
+         * the file system block size to be equal the page size, which means
+         * that we never have to deal with more than a single extent here.
+         */
+        error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
+        if (error)
+                goto unlock_entry;
+        if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
+                error = -EIO;           /* fs corruption? */
+                goto unlock_entry;
+        }
+
+        sector = iomap.blkno + (((pos & PAGE_MASK) - iomap.offset) >> 9);
+
+        if (vmf->cow_page) {
+                switch (iomap.type) {
+                case IOMAP_HOLE:
+                case IOMAP_UNWRITTEN:
+                        clear_user_highpage(vmf->cow_page, vaddr);
+                        break;
+                case IOMAP_MAPPED:
+                        error = copy_user_dax(iomap.bdev, sector, PAGE_SIZE,
+                                        vmf->cow_page, vaddr);
+                        break;
+                default:
+                        WARN_ON_ONCE(1);
+                        error = -EIO;
+                        break;
+                }
+
+                if (error)
+                        goto unlock_entry;
+                if (!radix_tree_exceptional_entry(entry)) {
+                        vmf->page = entry;
+                        return VM_FAULT_LOCKED;
+                }
+                vmf->entry = entry;
+                return VM_FAULT_DAX_LOCKED;
+        }
+
+        switch (iomap.type) {
+        case IOMAP_MAPPED:
+                if (iomap.flags & IOMAP_F_NEW) {
+                        count_vm_event(PGMAJFAULT);
+                        mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
+                        major = VM_FAULT_MAJOR;
+                }
+                error = dax_insert_mapping(mapping, iomap.bdev, sector,
+                                PAGE_SIZE, &entry, vma, vmf);
+                break;
+        case IOMAP_UNWRITTEN:
+        case IOMAP_HOLE:
+                if (!(vmf->flags & FAULT_FLAG_WRITE))
+                        return dax_load_hole(mapping, entry, vmf);
+                /*FALLTHRU*/
+        default:
+                WARN_ON_ONCE(1);
+                error = -EIO;
+                break;
+        }
+
+ unlock_entry:
+        put_locked_mapping_entry(mapping, vmf->pgoff, entry);
+ out:
+        if (error == -ENOMEM)
+                return VM_FAULT_OOM | major;
+        /* -EBUSY is fine, somebody else faulted on the same PTE */
+        if (error < 0 && error != -EBUSY)
+                return VM_FAULT_SIGBUS | major;
+        return VM_FAULT_NOPAGE | major;
+}
+EXPORT_SYMBOL_GPL(iomap_dax_fault);
+#endif /* CONFIG_FS_IOMAP */