19 files changed, 246 insertions, 293 deletions

diff --git a/Documentation/filesystems/dax.txt b/Documentation/filesystems/dax.txt
index 7bde64014a89..ce4587d257d2 100644
--- a/Documentation/filesystems/dax.txt
+++ b/Documentation/filesystems/dax.txt
@@ -79,6 +79,38 @@ These filesystems may be used for inspiration:
 - ext4: the fourth extended filesystem, see Documentation/filesystems/ext4.txt
 
 
+Handling Media Errors
+---------------------
+
+The libnvdimm subsystem stores a record of known media error locations for
+each pmem block device (in gendisk->badblocks). If we fault at such location,
+or one with a latent error not yet discovered, the application can expect
+to receive a SIGBUS. Libnvdimm also allows clearing of these errors by simply
+writing the affected sectors (through the pmem driver, and if the underlying
+NVDIMM supports the clear_poison DSM defined by ACPI).
+
+Since DAX IO normally doesn't go through the driver/bio path, applications or
+sysadmins have an option to restore the lost data from a prior backup/inbuilt
+redundancy in the following ways:
+
+1. Delete the affected file, and restore from a backup (sysadmin route):
+   This will free the file system blocks that were being used by the file,
+   and the next time they're allocated, they will be zeroed first, which
+   happens through the driver, and will clear bad sectors.
+
+2. Truncate or hole-punch the part of the file that has a bad-block (at least
+   an entire aligned sector has to be hole-punched, but not necessarily an
+   entire filesystem block).
+
+These are the two basic paths that allow DAX filesystems to continue operating
+in the presence of media errors. More robust error recovery mechanisms can be
+built on top of this in the future, for example, involving redundancy/mirroring
+provided at the block layer through DM, or additionally, at the filesystem
+level. These would have to rely on the above two tenets, that error clearing
+can happen either by sending an IO through the driver, or zeroing (also through
+the driver).
+
+
 Shortcomings
 ------------
 
diff --git a/arch/powerpc/sysdev/axonram.c b/arch/powerpc/sysdev/axonram.c
index 0d112b94d91d..ff75d70f7285 100644
--- a/arch/powerpc/sysdev/axonram.c
+++ b/arch/powerpc/sysdev/axonram.c
@@ -143,7 +143,7 @@ axon_ram_make_request(struct request_queue *queue, struct bio *bio)
  */
 static long
 axon_ram_direct_access(struct block_device *device, sector_t sector,
-                       void __pmem **kaddr, pfn_t *pfn)
+                       void __pmem **kaddr, pfn_t *pfn, long size)
 {
         struct axon_ram_bank *bank = device->bd_disk->private_data;
         loff_t offset = (loff_t)sector << AXON_RAM_SECTOR_SHIFT;
diff --git a/block/ioctl.c b/block/ioctl.c
index 698c7933d582..ed2397f8de9d 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -4,7 +4,6 @@
 #include <linux/gfp.h>
 #include <linux/blkpg.h>
 #include <linux/hdreg.h>
-#include <linux/badblocks.h>
 #include <linux/backing-dev.h>
 #include <linux/fs.h>
 #include <linux/blktrace_api.h>
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 51a071e32221..c04bd9bc39fd 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -381,7 +381,7 @@ static int brd_rw_page(struct block_device *bdev, sector_t sector,
 
 #ifdef CONFIG_BLK_DEV_RAM_DAX
 static long brd_direct_access(struct block_device *bdev, sector_t sector,
-                        void __pmem **kaddr, pfn_t *pfn)
+                        void __pmem **kaddr, pfn_t *pfn, long size)
 {
         struct brd_device *brd = bdev->bd_disk->private_data;
         struct page *page;
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 042baec56931..608fc4464574 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -164,14 +164,22 @@ static int pmem_rw_page(struct block_device *bdev, sector_t sector,
 }
 
 static long pmem_direct_access(struct block_device *bdev, sector_t sector,
-                      void __pmem **kaddr, pfn_t *pfn)
+                      void __pmem **kaddr, pfn_t *pfn, long size)
 {
         struct pmem_device *pmem = bdev->bd_queue->queuedata;
         resource_size_t offset = sector * 512 + pmem->data_offset;
 
+        if (unlikely(is_bad_pmem(&pmem->bb, sector, size)))
+                return -EIO;
         *kaddr = pmem->virt_addr + offset;
         *pfn = phys_to_pfn_t(pmem->phys_addr + offset, pmem->pfn_flags);
 
+        /*
+         * If badblocks are present, limit known good range to the
+         * requested range.
+         */
+        if (unlikely(pmem->bb.count))
+                return size;
         return pmem->size - pmem->pfn_pad - offset;
 }
 
diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index b83908670a9a..bed53c46dd90 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -31,7 +31,7 @@ static void dcssblk_release(struct gendisk *disk, fmode_t mode);
 static blk_qc_t dcssblk_make_request(struct request_queue *q,
                                                 struct bio *bio);
 static long dcssblk_direct_access(struct block_device *bdev, sector_t secnum,
-                         void __pmem **kaddr, pfn_t *pfn);
+                         void __pmem **kaddr, pfn_t *pfn, long size);
 
 static char dcssblk_segments[DCSSBLK_PARM_LEN] = "\0";
 
@@ -884,7 +884,7 @@ fail:
 
 static long
 dcssblk_direct_access (struct block_device *bdev, sector_t secnum,
-                        void __pmem **kaddr, pfn_t *pfn)
+                        void __pmem **kaddr, pfn_t *pfn, long size)
 {
         struct dcssblk_dev_info *dev_info;
         unsigned long offset, dev_sz;
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 1089dbf25925..71ccab1d22c6 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -51,6 +51,18 @@ struct block_device *I_BDEV(struct inode *inode)
 }
 EXPORT_SYMBOL(I_BDEV);
 
+void __vfs_msg(struct super_block *sb, const char *prefix, const char *fmt, ...)
+{
+        struct va_format vaf;
+        va_list args;
+
+        va_start(args, fmt);
+        vaf.fmt = fmt;
+        vaf.va = &args;
+        printk_ratelimited("%sVFS (%s): %pV\n", prefix, sb->s_id, &vaf);
+        va_end(args);
+}
+
 static void bdev_write_inode(struct block_device *bdev)
 {
         struct inode *inode = bdev->bd_inode;
@@ -489,7 +501,7 @@ long bdev_direct_access(struct block_device *bdev, struct blk_dax_ctl *dax)
         sector += get_start_sect(bdev);
         if (sector % (PAGE_SIZE / 512))
                 return -EINVAL;
-        avail = ops->direct_access(bdev, sector, &dax->addr, &dax->pfn);
+        avail = ops->direct_access(bdev, sector, &dax->addr, &dax->pfn, size);
         if (!avail)
                 return -ERANGE;
         if (avail > 0 && avail & ~PAGE_MASK)
@@ -498,6 +510,75 @@ long bdev_direct_access(struct block_device *bdev, struct blk_dax_ctl *dax)
 }
 EXPORT_SYMBOL_GPL(bdev_direct_access);
 
+/**
+ * bdev_dax_supported() - Check if the device supports dax for filesystem
+ * @sb: The superblock of the device
+ * @blocksize: The block size of the device
+ *
+ * This is a library function for filesystems to check if the block device
+ * can be mounted with dax option.
+ *
+ * Return: negative errno if unsupported, 0 if supported.
+ */
+int bdev_dax_supported(struct super_block *sb, int blocksize)
+{
+        struct blk_dax_ctl dax = {
+                .sector = 0,
+                .size = PAGE_SIZE,
+        };
+        int err;
+
+        if (blocksize != PAGE_SIZE) {
+                vfs_msg(sb, KERN_ERR, "error: unsupported blocksize for dax");
+                return -EINVAL;
+        }
+
+        err = bdev_direct_access(sb->s_bdev, &dax);
+        if (err < 0) {
+                switch (err) {
+                case -EOPNOTSUPP:
+                        vfs_msg(sb, KERN_ERR,
+                                "error: device does not support dax");
+                        break;
+                case -EINVAL:
+                        vfs_msg(sb, KERN_ERR,
+                                "error: unaligned partition for dax");
+                        break;
+                default:
+                        vfs_msg(sb, KERN_ERR,
+                                "error: dax access failed (%d)", err);
+                }
+                return err;
+        }
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(bdev_dax_supported);
+
+/**
+ * bdev_dax_capable() - Return if the raw device is capable for dax
+ * @bdev: The device for raw block device access
+ */
+bool bdev_dax_capable(struct block_device *bdev)
+{
+        struct blk_dax_ctl dax = {
+                .size = PAGE_SIZE,
+        };
+
+        if (!IS_ENABLED(CONFIG_FS_DAX))
+                return false;
+
+        dax.sector = 0;
+        if (bdev_direct_access(bdev, &dax) < 0)
+                return false;
+
+        dax.sector = bdev->bd_part->nr_sects - (PAGE_SIZE / 512);
+        if (bdev_direct_access(bdev, &dax) < 0)
+                return false;
+
+        return true;
+}
+
 /*
  * pseudo-fs
  */
@@ -1160,33 +1241,6 @@ void bd_set_size(struct block_device *bdev, loff_t size)
 }
 EXPORT_SYMBOL(bd_set_size);
 
-static bool blkdev_dax_capable(struct block_device *bdev)
-{
-        struct gendisk *disk = bdev->bd_disk;
-
-        if (!disk->fops->direct_access || !IS_ENABLED(CONFIG_FS_DAX))
-                return false;
-
-        /*
-         * If the partition is not aligned on a page boundary, we can't
-         * do dax I/O to it.
-         */
-        if ((bdev->bd_part->start_sect % (PAGE_SIZE / 512))
-                        || (bdev->bd_part->nr_sects % (PAGE_SIZE / 512)))
-                return false;
-
-        /*
-         * If the device has known bad blocks, force all I/O through the
-         * driver / page cache.
-         *
-         * TODO: support finer grained dax error handling
-         */
-        if (disk->bb && disk->bb->count)
-                return false;
-
-        return true;
-}
-
 static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part);
 
 /*
@@ -1266,7 +1320,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
 
                         if (!ret) {
                                 bd_set_size(bdev,(loff_t)get_capacity(disk)<<9);
-                                if (!blkdev_dax_capable(bdev))
+                                if (!bdev_dax_capable(bdev))
                                         bdev->bd_inode->i_flags &= ~S_DAX;
                         }
 
@@ -1303,7 +1357,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                                 goto out_clear;
                         }
                         bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9);
-                        if (!blkdev_dax_capable(bdev))
+                        if (!bdev_dax_capable(bdev))
                                 bdev->bd_inode->i_flags &= ~S_DAX;
                 }
         } else {
diff --git a/fs/dax.c b/fs/dax.c
index 7d9df93b3a14..5a282260d27e 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -87,50 +87,6 @@ struct page *read_dax_sector(struct block_device *bdev, sector_t n)
         return page;
 }
 
-/*
- * dax_clear_sectors() is called from within transaction context from XFS,
- * and hence this means the stack from this point must follow GFP_NOFS
- * semantics for all operations.
- */
-int dax_clear_sectors(struct block_device *bdev, sector_t _sector, long _size)
-{
-        struct blk_dax_ctl dax = {
-                .sector = _sector,
-                .size = _size,
-        };
-
-        might_sleep();
-        do {
-                long count, sz;
-
-                count = dax_map_atomic(bdev, &dax);
-                if (count < 0)
-                        return count;
-                sz = min_t(long, count, SZ_128K);
-                clear_pmem(dax.addr, sz);
-                dax.size -= sz;
-                dax.sector += sz / 512;
-                dax_unmap_atomic(bdev, &dax);
-                cond_resched();
-        } while (dax.size);
-
-        wmb_pmem();
-        return 0;
-}
-EXPORT_SYMBOL_GPL(dax_clear_sectors);
-
-/* the clear_pmem() calls are ordered by a wmb_pmem() in the caller */
-static void dax_new_buf(void __pmem *addr, unsigned size, unsigned first,
-                loff_t pos, loff_t end)
-{
-        loff_t final = end - pos + first; /* The final byte of the buffer */
-
-        if (first > 0)
-                clear_pmem(addr, first);
-        if (final < size)
-                clear_pmem(addr + final, size - final);
-}
-
 static bool buffer_written(struct buffer_head *bh)
 {
         return buffer_mapped(bh) && !buffer_unwritten(bh);
@@ -169,6 +125,9 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
         struct blk_dax_ctl dax = {
                 .addr = (void __pmem *) ERR_PTR(-EIO),
         };
+        unsigned blkbits = inode->i_blkbits;
+        sector_t file_blks = (i_size_read(inode) + (1 << blkbits) - 1)
+                                                                >> blkbits;
 
         if (rw == READ)
                 end = min(end, i_size_read(inode));
@@ -176,7 +135,6 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
         while (pos < end) {
                 size_t len;
                 if (pos == max) {
-                        unsigned blkbits = inode->i_blkbits;
                         long page = pos >> PAGE_SHIFT;
                         sector_t block = page << (PAGE_SHIFT - blkbits);
                         unsigned first = pos - (block << blkbits);
@@ -192,6 +150,13 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
                                         bh->b_size = 1 << blkbits;
                                 bh_max = pos - first + bh->b_size;
                                 bdev = bh->b_bdev;
+                                /*
+                                 * We allow uninitialized buffers for writes
+                                 * beyond EOF as those cannot race with faults
+                                 */
+                                WARN_ON_ONCE(
+                                        (buffer_new(bh) && block < file_blks) ||
+                                        (rw == WRITE && buffer_unwritten(bh)));
                         } else {
                                 unsigned done = bh->b_size -
                                                 (bh_max - (pos - first));
@@ -211,11 +176,6 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
                                         rc = map_len;
                                         break;
                                 }
-                                if (buffer_unwritten(bh) || buffer_new(bh)) {
-                                        dax_new_buf(dax.addr, map_len, first,
-                                                        pos, end);
-                                        need_wmb = true;
-                                }
                                 dax.addr += first;
                                 size = map_len - first;
                         }
@@ -276,15 +236,8 @@ ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
         memset(&bh, 0, sizeof(bh));
         bh.b_bdev = inode->i_sb->s_bdev;
 
-        if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ) {
-                struct address_space *mapping = inode->i_mapping;
+        if ((flags & DIO_LOCKING) && iov_iter_rw(iter) == READ)
                 inode_lock(inode);
-                retval = filemap_write_and_wait_range(mapping, pos, end - 1);
-                if (retval) {
-                        inode_unlock(inode);
-                        goto out;
-                }
-        }
 
         /* Protects against truncate */
         if (!(flags & DIO_SKIP_DIO_COUNT))
@@ -305,7 +258,6 @@ ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
 
         if (!(flags & DIO_SKIP_DIO_COUNT))
                 inode_dio_end(inode);
- out:
         return retval;
 }
 EXPORT_SYMBOL_GPL(dax_do_io);
@@ -321,20 +273,11 @@ EXPORT_SYMBOL_GPL(dax_do_io);
 static int dax_load_hole(struct address_space *mapping, struct page *page,
                                                         struct vm_fault *vmf)
 {
-        unsigned long size;
-        struct inode *inode = mapping->host;
         if (!page)
                 page = find_or_create_page(mapping, vmf->pgoff,
                                                 GFP_KERNEL | __GFP_ZERO);
         if (!page)
                 return VM_FAULT_OOM;
-        /* Recheck i_size under page lock to avoid truncate race */
-        size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
-        if (vmf->pgoff >= size) {
-                unlock_page(page);
-                put_page(page);
-                return VM_FAULT_SIGBUS;
-        }
 
         vmf->page = page;
         return VM_FAULT_LOCKED;
@@ -565,33 +508,14 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
                 .sector = to_sector(bh, inode),
                 .size = bh->b_size,
         };
-        pgoff_t size;
         int error;
 
         i_mmap_lock_read(mapping);
 
-        /*
-         * Check truncate didn't happen while we were allocating a block.
-         * If it did, this block may or may not be still allocated to the
-         * file.  We can't tell the filesystem to free it because we can't
-         * take i_mutex here.  In the worst case, the file still has blocks
-         * allocated past the end of the file.
-         */
-        size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
-        if (unlikely(vmf->pgoff >= size)) {
-                error = -EIO;
-                goto out;
-        }
-
         if (dax_map_atomic(bdev, &dax) < 0) {
                 error = PTR_ERR(dax.addr);
                 goto out;
         }
-
-        if (buffer_unwritten(bh) || buffer_new(bh)) {
-                clear_pmem(dax.addr, PAGE_SIZE);
-                wmb_pmem();
-        }
         dax_unmap_atomic(bdev, &dax);
 
         error = dax_radix_entry(mapping, vmf->pgoff, dax.sector, false,
@@ -612,19 +536,13 @@ static int dax_insert_mapping(struct inode *inode, struct buffer_head *bh,
  * @vma: The virtual memory area where the fault occurred
  * @vmf: The description of the fault
  * @get_block: The filesystem method used to translate file offsets to blocks
- * @complete_unwritten: The filesystem method used to convert unwritten blocks
- *      to written so the data written to them is exposed. This is required for
- *      required by write faults for filesystems that will return unwritten
- *      extent mappings from @get_block, but it is optional for reads as
- *      dax_insert_mapping() will always zero unwritten blocks. If the fs does
- *      not support unwritten extents, the it should pass NULL.
  *
  * When a page fault occurs, filesystems may call this helper in their
  * fault handler for DAX files. __dax_fault() assumes the caller has done all
  * the necessary locking for the page fault to proceed successfully.
  */
 int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
-                        get_block_t get_block, dax_iodone_t complete_unwritten)
+                        get_block_t get_block)
 {
         struct file *file = vma->vm_file;
         struct address_space *mapping = file->f_mapping;
@@ -659,15 +577,6 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
                         put_page(page);
                         goto repeat;
                 }
-                size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
-                if (unlikely(vmf->pgoff >= size)) {
-                        /*
-                         * We have a struct page covering a hole in the file
-                         * from a read fault and we've raced with a truncate
-                         */
-                        error = -EIO;
-                        goto unlock_page;
-                }
         }
 
         error = get_block(inode, block, &bh, 0);
@@ -700,17 +609,8 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
                 if (error)
                         goto unlock_page;
                 vmf->page = page;
-                if (!page) {
+                if (!page)
                         i_mmap_lock_read(mapping);
-                        /* Check we didn't race with truncate */
-                        size = (i_size_read(inode) + PAGE_SIZE - 1) >>
-                                                                PAGE_SHIFT;
-                        if (vmf->pgoff >= size) {
-                                i_mmap_unlock_read(mapping);
-                                error = -EIO;
-                                goto out;
-                        }
-                }
                 return VM_FAULT_LOCKED;
         }
 
@@ -727,23 +627,9 @@ int __dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
                 page = NULL;
         }
 
-        /*
-         * If we successfully insert the new mapping over an unwritten extent,
-         * we need to ensure we convert the unwritten extent. If there is an
-         * error inserting the mapping, the filesystem needs to leave it as
-         * unwritten to prevent exposure of the stale underlying data to
-         * userspace, but we still need to call the completion function so
-         * the private resources on the mapping buffer can be released. We
-         * indicate what the callback should do via the uptodate variable, same
-         * as for normal BH based IO completions.
-         */
+        /* Filesystem should not return unwritten buffers to us! */
+        WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh));
         error = dax_insert_mapping(inode, &bh, vma, vmf);
-        if (buffer_unwritten(&bh)) {
-                if (complete_unwritten)
-                        complete_unwritten(&bh, !error);
-                else
-                        WARN_ON_ONCE(!(vmf->flags & FAULT_FLAG_WRITE));
-        }
 
  out:
         if (error == -ENOMEM)
@@ -772,7 +658,7 @@ EXPORT_SYMBOL(__dax_fault);
  * fault handler for DAX files.
  */
 int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
-              get_block_t get_block, dax_iodone_t complete_unwritten)
+              get_block_t get_block)
 {
         int result;
         struct super_block *sb = file_inode(vma->vm_file)->i_sb;
@@ -781,7 +667,7 @@ int dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
                 sb_start_pagefault(sb);
                 file_update_time(vma->vm_file);
         }
-        result = __dax_fault(vma, vmf, get_block, complete_unwritten);
+        result = __dax_fault(vma, vmf, get_block);
         if (vmf->flags & FAULT_FLAG_WRITE)
                 sb_end_pagefault(sb);
 
@@ -815,8 +701,7 @@ static void __dax_dbg(struct buffer_head *bh, unsigned long address,
 #define dax_pmd_dbg(bh, address, reason)        __dax_dbg(bh, address, reason, "dax_pmd")
 
 int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
-                pmd_t *pmd, unsigned int flags, get_block_t get_block,
-                dax_iodone_t complete_unwritten)
+                pmd_t *pmd, unsigned int flags, get_block_t get_block)
 {
         struct file *file = vma->vm_file;
         struct address_space *mapping = file->f_mapping;
@@ -875,6 +760,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
                 if (get_block(inode, block, &bh, 1) != 0)
                         return VM_FAULT_SIGBUS;
                 alloc = true;
+                WARN_ON_ONCE(buffer_unwritten(&bh) || buffer_new(&bh));
         }
 
         bdev = bh.b_bdev;
@@ -902,23 +788,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
 
         i_mmap_lock_read(mapping);
 
-        /*
-         * If a truncate happened while we were allocating blocks, we may
-         * leave blocks allocated to the file that are beyond EOF.  We can't
-         * take i_mutex here, so just leave them hanging; they'll be freed
-         * when the file is deleted.
-         */
-        size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
-        if (pgoff >= size) {
-                result = VM_FAULT_SIGBUS;
-                goto out;
-        }
-        if ((pgoff | PG_PMD_COLOUR) >= size) {
-                dax_pmd_dbg(&bh, address,
-                                "offset + huge page size > file size");
-                goto fallback;
-        }
-
         if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
                 spinlock_t *ptl;
                 pmd_t entry;
@@ -954,8 +823,8 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
                 long length = dax_map_atomic(bdev, &dax);
 
                 if (length < 0) {
-                        result = VM_FAULT_SIGBUS;
-                        goto out;
+                        dax_pmd_dbg(&bh, address, "dax-error fallback");
+                        goto fallback;
                 }
                 if (length < PMD_SIZE) {
                         dax_pmd_dbg(&bh, address, "dax-length too small");
@@ -973,14 +842,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
                         dax_pmd_dbg(&bh, address, "pfn not in memmap");
                         goto fallback;
                 }
-
-                if (buffer_unwritten(&bh) || buffer_new(&bh)) {
-                        clear_pmem(dax.addr, PMD_SIZE);
-                        wmb_pmem();
-                        count_vm_event(PGMAJFAULT);
-                        mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
-                        result |= VM_FAULT_MAJOR;
-                }
                 dax_unmap_atomic(bdev, &dax);
 
                 /*
@@ -1020,9 +881,6 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
  out:
         i_mmap_unlock_read(mapping);
 
-        if (buffer_unwritten(&bh))
-                complete_unwritten(&bh, !(result & VM_FAULT_ERROR));
-
         return result;
 
  fallback:
@@ -1042,8 +900,7 @@ EXPORT_SYMBOL_GPL(__dax_pmd_fault);
  * pmd_fault handler for DAX files.
  */
 int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
-                        pmd_t *pmd, unsigned int flags, get_block_t get_block,
-                        dax_iodone_t complete_unwritten)
+                        pmd_t *pmd, unsigned int flags, get_block_t get_block)
 {
         int result;
         struct super_block *sb = file_inode(vma->vm_file)->i_sb;
@@ -1052,8 +909,7 @@ int dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
                 sb_start_pagefault(sb);
                 file_update_time(vma->vm_file);
         }
-        result = __dax_pmd_fault(vma, address, pmd, flags, get_block,
-                                complete_unwritten);
+        result = __dax_pmd_fault(vma, address, pmd, flags, get_block);
         if (flags & FAULT_FLAG_WRITE)
                 sb_end_pagefault(sb);
 
@@ -1091,6 +947,43 @@ int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 }
 EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
 
+static bool dax_range_is_aligned(struct block_device *bdev,
+                                 unsigned int offset, unsigned int length)
+{
+        unsigned short sector_size = bdev_logical_block_size(bdev);
+
+        if (!IS_ALIGNED(offset, sector_size))
+                return false;
+        if (!IS_ALIGNED(length, sector_size))
+                return false;
+
+        return true;
+}
+
+int __dax_zero_page_range(struct block_device *bdev, sector_t sector,
+                unsigned int offset, unsigned int length)
+{
+        struct blk_dax_ctl dax = {
+                .sector         = sector,
+                .size           = PAGE_SIZE,
+        };
+
+        if (dax_range_is_aligned(bdev, offset, length)) {
+                sector_t start_sector = dax.sector + (offset >> 9);
+
+                return blkdev_issue_zeroout(bdev, start_sector,
+                                length >> 9, GFP_NOFS, true);
+        } else {
+                if (dax_map_atomic(bdev, &dax) < 0)
+                        return PTR_ERR(dax.addr);
+                clear_pmem(dax.addr + offset, length);
+                wmb_pmem();
+                dax_unmap_atomic(bdev, &dax);
+        }
+        return 0;
+}
+EXPORT_SYMBOL_GPL(__dax_zero_page_range);
+
 /**
  * dax_zero_page_range - zero a range within a page of a DAX file
  * @inode: The file being truncated
@@ -1102,12 +995,6 @@ EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
  * page in a DAX file.  This is intended for hole-punch operations.  If
  * you are truncating a file, the helper function dax_truncate_page() may be
  * more convenient.
- *
- * We work in terms of PAGE_SIZE here for commonality with
- * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
- * took care of disposing of the unnecessary blocks.  Even if the filesystem
- * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
- * since the file might be mmapped.
  */
 int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
                                                         get_block_t get_block)
@@ -1126,23 +1013,11 @@ int dax_zero_page_range(struct inode *inode, loff_t from, unsigned length,
         bh.b_bdev = inode->i_sb->s_bdev;
         bh.b_size = PAGE_SIZE;
         err = get_block(inode, index, &bh, 0);
-        if (err < 0)
+        if (err < 0 || !buffer_written(&bh))
                 return err;
-        if (buffer_written(&bh)) {
-                struct block_device *bdev = bh.b_bdev;
-                struct blk_dax_ctl dax = {
-                        .sector = to_sector(&bh, inode),
-                        .size = PAGE_SIZE,
-                };
-
-                if (dax_map_atomic(bdev, &dax) < 0)
-                        return PTR_ERR(dax.addr);
-                clear_pmem(dax.addr + offset, length);
-                wmb_pmem();
-                dax_unmap_atomic(bdev, &dax);
-        }
 
-        return 0;
+        return __dax_zero_page_range(bh.b_bdev, to_sector(&bh, inode),
+                        offset, length);
 }
 EXPORT_SYMBOL_GPL(dax_zero_page_range);
 
@@ -1154,12 +1029,6 @@ EXPORT_SYMBOL_GPL(dax_zero_page_range);
  *
  * Similar to block_truncate_page(), this function can be called by a
  * filesystem when it is truncating a DAX file to handle the partial page.
- *
- * We work in terms of PAGE_SIZE here for commonality with
- * block_truncate_page(), but we could go down to PAGE_SIZE if the filesystem
- * took care of disposing of the unnecessary blocks.  Even if the filesystem
- * block size is smaller than PAGE_SIZE, we have to zero the rest of the page
- * since the file might be mmapped.
  */
 int dax_truncate_page(struct inode *inode, loff_t from, get_block_t get_block)
 {
diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index c1400b109805..868c02317b05 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -51,7 +51,7 @@ static int ext2_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
         }
         down_read(&ei->dax_sem);
 
-        ret = __dax_fault(vma, vmf, ext2_get_block, NULL);
+        ret = __dax_fault(vma, vmf, ext2_get_block);
 
         up_read(&ei->dax_sem);
         if (vmf->flags & FAULT_FLAG_WRITE)
@@ -72,7 +72,7 @@ static int ext2_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
         }
         down_read(&ei->dax_sem);
 
-        ret = __dax_pmd_fault(vma, addr, pmd, flags, ext2_get_block, NULL);
+        ret = __dax_pmd_fault(vma, addr, pmd, flags, ext2_get_block);
 
         up_read(&ei->dax_sem);
         if (flags & FAULT_FLAG_WRITE)
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index b675610391b8..fcbe58641e40 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -26,6 +26,7 @@
 #include <linux/highuid.h>
 #include <linux/pagemap.h>
 #include <linux/dax.h>
+#include <linux/blkdev.h>
 #include <linux/quotaops.h>
 #include <linux/writeback.h>
 #include <linux/buffer_head.h>
@@ -737,19 +738,18 @@ static int ext2_get_blocks(struct inode *inode,
                  * so that it's not found by another thread before it's
                  * initialised
                  */
-                err = dax_clear_sectors(inode->i_sb->s_bdev,
-                                le32_to_cpu(chain[depth-1].key) <<
-                                (inode->i_blkbits - 9),
-                                1 << inode->i_blkbits);
+                err = sb_issue_zeroout(inode->i_sb,
+                                le32_to_cpu(chain[depth-1].key), count,
+                                GFP_NOFS);
                 if (err) {
                         mutex_unlock(&ei->truncate_mutex);
                         goto cleanup;
                 }
-        }
+        } else
+                set_buffer_new(bh_result);
 
         ext2_splice_branch(inode, iblock, partial, indirect_blks, count);
         mutex_unlock(&ei->truncate_mutex);
-        set_buffer_new(bh_result);
 got_it:
         map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
         if (count > blocks_to_boundary)
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index b78caf25f746..1d9379568aa8 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -922,16 +922,9 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
         blocksize = BLOCK_SIZE << le32_to_cpu(sbi->s_es->s_log_block_size);
 
         if (sbi->s_mount_opt & EXT2_MOUNT_DAX) {
-                if (blocksize != PAGE_SIZE) {
-                        ext2_msg(sb, KERN_ERR,
-                                        "error: unsupported blocksize for dax");
+                err = bdev_dax_supported(sb, blocksize);
+                if (err)
                         goto failed_mount;
-                }
-                if (!sb->s_bdev->bd_disk->fops->direct_access) {
-                        ext2_msg(sb, KERN_ERR,
-                                        "error: device does not support dax");
-                        goto failed_mount;
-                }
         }
 
         /* If the blocksize doesn't match, re-read the thing.. */
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index d478110c32a6..df44c877892a 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -202,7 +202,7 @@ static int ext4_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
         if (IS_ERR(handle))
                 result = VM_FAULT_SIGBUS;
         else
-                result = __dax_fault(vma, vmf, ext4_dax_get_block, NULL);
+                result = __dax_fault(vma, vmf, ext4_dax_get_block);
 
         if (write) {
                 if (!IS_ERR(handle))
@@ -238,7 +238,7 @@ static int ext4_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
                 result = VM_FAULT_SIGBUS;
         else
                 result = __dax_pmd_fault(vma, addr, pmd, flags,
-                                         ext4_dax_get_block, NULL);
+                                         ext4_dax_get_block);
 
         if (write) {
                 if (!IS_ERR(handle))
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 20c5d52253b4..3822a5aedc61 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3417,16 +3417,9 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
         }
 
         if (sbi->s_mount_opt & EXT4_MOUNT_DAX) {
-                if (blocksize != PAGE_SIZE) {
-                        ext4_msg(sb, KERN_ERR,
-                                        "error: unsupported blocksize for dax");
-                        goto failed_mount;
-                }
-                if (!sb->s_bdev->bd_disk->fops->direct_access) {
-                        ext4_msg(sb, KERN_ERR,
-                                        "error: device does not support dax");
+                err = bdev_dax_supported(sb, blocksize);
+                if (err)
                         goto failed_mount;
-                }
         }
 
         if (ext4_has_feature_encrypt(sb) && es->s_encryption_level) {
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index 613ea2d7ac19..586bb64e674b 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -72,18 +72,11 @@ xfs_zero_extent(
         struct xfs_mount *mp = ip->i_mount;
         xfs_daddr_t     sector = xfs_fsb_to_db(ip, start_fsb);
         sector_t        block = XFS_BB_TO_FSBT(mp, sector);
-        ssize_t         size = XFS_FSB_TO_B(mp, count_fsb);
-
-        if (IS_DAX(VFS_I(ip)))
-                return dax_clear_sectors(xfs_find_bdev_for_inode(VFS_I(ip)),
-                                sector, size);
-
-        /*
-         * let the block layer decide on the fastest method of
-         * implementing the zeroing.
-         */
-        return sb_issue_zeroout(mp->m_super, block, count_fsb, GFP_NOFS);
 
+        return blkdev_issue_zeroout(xfs_find_bdev_for_inode(VFS_I(ip)),
+                block << (mp->m_super->s_blocksize_bits - 9),
+                count_fsb << (mp->m_super->s_blocksize_bits - 9),
+                GFP_NOFS, true);
 }
 
 /*
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 44af22897c8b..47fc63295422 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1551,7 +1551,7 @@ xfs_filemap_page_mkwrite(
         xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
         if (IS_DAX(inode)) {
-                ret = __dax_mkwrite(vma, vmf, xfs_get_blocks_dax_fault, NULL);
+                ret = __dax_mkwrite(vma, vmf, xfs_get_blocks_dax_fault);
         } else {
                 ret = block_page_mkwrite(vma, vmf, xfs_get_blocks);
                 ret = block_page_mkwrite_return(ret);
@@ -1585,7 +1585,7 @@ xfs_filemap_fault(
                  * changes to xfs_get_blocks_direct() to map unwritten extent
                  * ioend for conversion on read-only mappings.
                  */
-                ret = __dax_fault(vma, vmf, xfs_get_blocks_dax_fault, NULL);
+                ret = __dax_fault(vma, vmf, xfs_get_blocks_dax_fault);
         } else
                 ret = filemap_fault(vma, vmf);
         xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
@@ -1622,8 +1622,7 @@ xfs_filemap_pmd_fault(
         }
 
         xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
-        ret = __dax_pmd_fault(vma, addr, pmd, flags, xfs_get_blocks_dax_fault,
-                              NULL);
+        ret = __dax_pmd_fault(vma, addr, pmd, flags, xfs_get_blocks_dax_fault);
         xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
 
         if (flags & FAULT_FLAG_WRITE)
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 416421d7ff10..11ea5d51db56 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1555,14 +1555,12 @@ xfs_fs_fill_super(
 
         if (mp->m_flags & XFS_MOUNT_DAX) {
                 xfs_warn(mp,
-        "DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
-                if (sb->s_blocksize != PAGE_SIZE) {
-                        xfs_alert(mp,
-                "Filesystem block size invalid for DAX Turning DAX off.");
-                        mp->m_flags &= ~XFS_MOUNT_DAX;
-                } else if (!sb->s_bdev->bd_disk->fops->direct_access) {
+                "DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
+
+                error = bdev_dax_supported(sb, sb->s_blocksize);
+                if (error) {
                         xfs_alert(mp,
-                "Block device does not support DAX Turning DAX off.");
+                        "DAX unsupported by block device. Turning off DAX.");
                         mp->m_flags &= ~XFS_MOUNT_DAX;
                 }
         }
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 1fd8fdff2f81..3d9cf326574f 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -768,6 +768,17 @@ static inline void rq_flush_dcache_pages(struct request *rq)
 }
 #endif
 
+#ifdef CONFIG_PRINTK
+#define vfs_msg(sb, level, fmt, ...)                            \
+        __vfs_msg(sb, level, fmt, ##__VA_ARGS__)
+#else
+#define vfs_msg(sb, level, fmt, ...)                            \
+do {                                                            \
+        no_printk(fmt, ##__VA_ARGS__);                          \
+        __vfs_msg(sb, "", " ");                                 \
+} while (0)
+#endif
+
 extern int blk_register_queue(struct gendisk *disk);
 extern void blk_unregister_queue(struct gendisk *disk);
 extern blk_qc_t generic_make_request(struct bio *bio);
@@ -1660,7 +1671,7 @@ struct block_device_operations {
         int (*ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
         int (*compat_ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
         long (*direct_access)(struct block_device *, sector_t, void __pmem **,
-                        pfn_t *);
+                        pfn_t *, long);
         unsigned int (*check_events) (struct gendisk *disk,
                                       unsigned int clearing);
         /* ->media_changed() is DEPRECATED, use ->check_events() instead */
@@ -1680,6 +1691,8 @@ extern int bdev_read_page(struct block_device *, sector_t, struct page *);
 extern int bdev_write_page(struct block_device *, sector_t, struct page *,
                                                 struct writeback_control *);
 extern long bdev_direct_access(struct block_device *, struct blk_dax_ctl *);
+extern int bdev_dax_supported(struct super_block *, int);
+extern bool bdev_dax_capable(struct block_device *);
 #else /* CONFIG_BLOCK */
 
 struct block_device;
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 982a6c4a62f3..7743e51f826c 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -7,41 +7,44 @@
 
 ssize_t dax_do_io(struct kiocb *, struct inode *, struct iov_iter *,
                   get_block_t, dio_iodone_t, int flags);
-int dax_clear_sectors(struct block_device *bdev, sector_t _sector, long _size);
 int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t);
 int dax_truncate_page(struct inode *, loff_t from, get_block_t);
-int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t,
-                dax_iodone_t);
-int __dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t,
-                dax_iodone_t);
+int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
+int __dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
 
 #ifdef CONFIG_FS_DAX
 struct page *read_dax_sector(struct block_device *bdev, sector_t n);
+int __dax_zero_page_range(struct block_device *bdev, sector_t sector,
+                unsigned int offset, unsigned int length);
 #else
 static inline struct page *read_dax_sector(struct block_device *bdev,
                 sector_t n)
 {
         return ERR_PTR(-ENXIO);
 }
+static inline int __dax_zero_page_range(struct block_device *bdev,
+                sector_t sector, unsigned int offset, unsigned int length)
+{
+        return -ENXIO;
+}
 #endif
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 int dax_pmd_fault(struct vm_area_struct *, unsigned long addr, pmd_t *,
-                                unsigned int flags, get_block_t, dax_iodone_t);
+                                unsigned int flags, get_block_t);
 int __dax_pmd_fault(struct vm_area_struct *, unsigned long addr, pmd_t *,
-                                unsigned int flags, get_block_t, dax_iodone_t);
+                                unsigned int flags, get_block_t);
 #else
 static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
-                                pmd_t *pmd, unsigned int flags, get_block_t gb,
-                                dax_iodone_t di)
+                                pmd_t *pmd, unsigned int flags, get_block_t gb)
 {
         return VM_FAULT_FALLBACK;
 }
 #define __dax_pmd_fault dax_pmd_fault
 #endif
 int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
-#define dax_mkwrite(vma, vmf, gb, iod)          dax_fault(vma, vmf, gb, iod)
-#define __dax_mkwrite(vma, vmf, gb, iod)        __dax_fault(vma, vmf, gb, iod)
+#define dax_mkwrite(vma, vmf, gb)       dax_fault(vma, vmf, gb)
+#define __dax_mkwrite(vma, vmf, gb)     __dax_fault(vma, vmf, gb)
 
 static inline bool vma_is_dax(struct vm_area_struct *vma)
 {
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 5f61431d8673..9ace7f745bcd 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -74,7 +74,6 @@ typedef int (get_block_t)(struct inode *inode, sector_t iblock,
                         struct buffer_head *bh_result, int create);
 typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
                         ssize_t bytes, void *private);
-typedef void (dax_iodone_t)(struct buffer_head *bh_map, int uptodate);
 
 #define MAY_EXEC                0x00000001
 #define MAY_WRITE               0x00000002