ext2: use iomap to implement DAX

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

4 files changed, 129 insertions, 12 deletions

diff --git a/fs/ext2/Kconfig b/fs/ext2/Kconfig
index c634874e12d9..36bea5adcaba 100644
--- a/fs/ext2/Kconfig
+++ b/fs/ext2/Kconfig
@@ -1,5 +1,6 @@
 config EXT2_FS
         tristate "Second extended fs support"
+        select FS_IOMAP if FS_DAX
         help
           Ext2 is a standard Linux file system for hard disks.
 
diff --git a/fs/ext2/ext2.h b/fs/ext2/ext2.h
index 06af2f92226c..37e2be784ac7 100644
--- a/fs/ext2/ext2.h
+++ b/fs/ext2/ext2.h
@@ -814,6 +814,7 @@ extern const struct file_operations ext2_file_operations;
 /* inode.c */
 extern const struct address_space_operations ext2_aops;
 extern const struct address_space_operations ext2_nobh_aops;
+extern struct iomap_ops ext2_iomap_ops;
 
 /* namei.c */
 extern const struct inode_operations ext2_dir_inode_operations;
diff --git a/fs/ext2/file.c b/fs/ext2/file.c
index 5efeefe17abb..423cc01c9d41 100644
--- a/fs/ext2/file.c
+++ b/fs/ext2/file.c
@@ -22,11 +22,59 @@
 #include <linux/pagemap.h>
 #include <linux/dax.h>
 #include <linux/quotaops.h>
+#include <linux/iomap.h>
+#include <linux/uio.h>
 #include "ext2.h"
 #include "xattr.h"
 #include "acl.h"
 
 #ifdef CONFIG_FS_DAX
+static ssize_t ext2_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+        struct inode *inode = iocb->ki_filp->f_mapping->host;
+        ssize_t ret;
+
+        if (!iov_iter_count(to))
+                return 0; /* skip atime */
+
+        inode_lock_shared(inode);
+        ret = iomap_dax_rw(iocb, to, &ext2_iomap_ops);
+        inode_unlock_shared(inode);
+
+        file_accessed(iocb->ki_filp);
+        return ret;
+}
+
+static ssize_t ext2_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+        struct file *file = iocb->ki_filp;
+        struct inode *inode = file->f_mapping->host;
+        ssize_t ret;
+
+        inode_lock(inode);
+        ret = generic_write_checks(iocb, from);
+        if (ret <= 0)
+                goto out_unlock;
+        ret = file_remove_privs(file);
+        if (ret)
+                goto out_unlock;
+        ret = file_update_time(file);
+        if (ret)
+                goto out_unlock;
+
+        ret = iomap_dax_rw(iocb, from, &ext2_iomap_ops);
+        if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
+                i_size_write(inode, iocb->ki_pos);
+                mark_inode_dirty(inode);
+        }
+
+out_unlock:
+        inode_unlock(inode);
+        if (ret > 0)
+                ret = generic_write_sync(iocb, ret);
+        return ret;
+}
+
 /*
  * The lock ordering for ext2 DAX fault paths is:
  *
@@ -51,7 +99,7 @@ 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);
+        ret = iomap_dax_fault(vma, vmf, &ext2_iomap_ops);
 
         up_read(&ei->dax_sem);
         if (vmf->flags & FAULT_FLAG_WRITE)
@@ -156,14 +204,28 @@ int ext2_fsync(struct file *file, loff_t start, loff_t end, int datasync)
         return ret;
 }
 
-/*
- * We have mostly NULL's here: the current defaults are ok for
- * the ext2 filesystem.
- */
+static ssize_t ext2_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+#ifdef CONFIG_FS_DAX
+        if (IS_DAX(iocb->ki_filp->f_mapping->host))
+                return ext2_dax_read_iter(iocb, to);
+#endif
+        return generic_file_read_iter(iocb, to);
+}
+
+static ssize_t ext2_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+#ifdef CONFIG_FS_DAX
+        if (IS_DAX(iocb->ki_filp->f_mapping->host))
+                return ext2_dax_write_iter(iocb, from);
+#endif
+        return generic_file_write_iter(iocb, from);
+}
+
 const struct file_operations ext2_file_operations = {
         .llseek         = generic_file_llseek,
-        .read_iter      = generic_file_read_iter,
-        .write_iter     = generic_file_write_iter,
+        .read_iter      = ext2_file_read_iter,
+        .write_iter     = ext2_file_write_iter,
         .unlocked_ioctl = ext2_ioctl,
 #ifdef CONFIG_COMPAT
         .compat_ioctl   = ext2_compat_ioctl,
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 2a69ab2e7bb0..aae5f61f980b 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -32,6 +32,7 @@
 #include <linux/buffer_head.h>
 #include <linux/mpage.h>
 #include <linux/fiemap.h>
+#include <linux/iomap.h>
 #include <linux/namei.h>
 #include <linux/uio.h>
 #include "ext2.h"
@@ -787,6 +788,59 @@ int ext2_get_block(struct inode *inode, sector_t iblock,
 
 }
 
+#ifdef CONFIG_FS_DAX
+static int ext2_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
+                unsigned flags, struct iomap *iomap)
+{
+        unsigned int blkbits = inode->i_blkbits;
+        unsigned long first_block = offset >> blkbits;
+        unsigned long max_blocks = (length + (1 << blkbits) - 1) >> blkbits;
+        bool new = false, boundary = false;
+        u32 bno;
+        int ret;
+
+        ret = ext2_get_blocks(inode, first_block, max_blocks,
+                        &bno, &new, &boundary, flags & IOMAP_WRITE);
+        if (ret < 0)
+                return ret;
+
+        iomap->flags = 0;
+        iomap->bdev = inode->i_sb->s_bdev;
+        iomap->offset = first_block << blkbits;
+
+        if (ret == 0) {
+                iomap->type = IOMAP_HOLE;
+                iomap->blkno = IOMAP_NULL_BLOCK;
+                iomap->length = 1 << blkbits;
+        } else {
+                iomap->type = IOMAP_MAPPED;
+                iomap->blkno = (sector_t)bno << (blkbits - 9);
+                iomap->length = (u64)ret << blkbits;
+                iomap->flags |= IOMAP_F_MERGED;
+        }
+
+        if (new)
+                iomap->flags |= IOMAP_F_NEW;
+        return 0;
+}
+
+static int
+ext2_iomap_end(struct inode *inode, loff_t offset, loff_t length,
+                ssize_t written, unsigned flags, struct iomap *iomap)
+{
+        if (iomap->type == IOMAP_MAPPED &&
+            written < length &&
+            (flags & IOMAP_WRITE))
+                ext2_write_failed(inode->i_mapping, offset + length);
+        return 0;
+}
+
+struct iomap_ops ext2_iomap_ops = {
+        .iomap_begin            = ext2_iomap_begin,
+        .iomap_end              = ext2_iomap_end,
+};
+#endif /* CONFIG_FS_DAX */
+
 int ext2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
                 u64 start, u64 len)
 {
@@ -872,11 +926,10 @@ ext2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
         loff_t offset = iocb->ki_pos;
         ssize_t ret;
 
-        if (IS_DAX(inode))
-                ret = dax_do_io(iocb, inode, iter, ext2_get_block, NULL,
-                                DIO_LOCKING);
-        else
-                ret = blockdev_direct_IO(iocb, inode, iter, ext2_get_block);
+        if (WARN_ON_ONCE(IS_DAX(inode)))
+                return -EIO;
+
+        ret = blockdev_direct_IO(iocb, inode, iter, ext2_get_block);
         if (ret < 0 && iov_iter_rw(iter) == WRITE)
                 ext2_write_failed(mapping, offset + count);
         return ret;