iomap: add a IOMAP_DAX flag

Add a flag so that the file system can easily detect DAX operations
based just on the iomap operation requested instead of looking at
inode state using IS_DAX.  This will be needed to apply the to be
added partition offset only for operations that actually use DAX,
but not things like fiemap that are based on the block device.
In the long run it should also allow turning the bdev, dax_dev
and inline_data into a union.

Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Dan Williams <[email protected]>
Reviewed-by: Darrick J. Wong <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Dan Williams <[email protected]>

Author: Christoph Hellwig

fs/dax.c

@@ -1180,7 +1180,7 @@ int dax_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
 		.inode		= inode,
 		.pos		= pos,
 		.len		= len,
-		.flags		= IOMAP_ZERO,
+		.flags		= IOMAP_DAX | IOMAP_ZERO,
 	};
 	int ret;
 
@@ -1308,6 +1308,7 @@ dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		.inode		= iocb->ki_filp->f_mapping->host,
 		.pos		= iocb->ki_pos,
 		.len		= iov_iter_count(iter),
+		.flags		= IOMAP_DAX,
 	};
 	loff_t done = 0;
 	int ret;
@@ -1461,7 +1462,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 		.inode		= mapping->host,
 		.pos		= (loff_t)vmf->pgoff << PAGE_SHIFT,
 		.len		= PAGE_SIZE,
-		.flags		= IOMAP_FAULT,
+		.flags		= IOMAP_DAX | IOMAP_FAULT,
 	};
 	vm_fault_t ret = 0;
 	void *entry;
@@ -1570,7 +1571,7 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
 	struct iomap_iter iter = {
 		.inode		= mapping->host,
 		.len		= PMD_SIZE,
-		.flags		= IOMAP_FAULT,
+		.flags		= IOMAP_DAX | IOMAP_FAULT,
 	};
 	vm_fault_t ret = VM_FAULT_FALLBACK;
 	pgoff_t max_pgoff;

fs/ext4/inode.c

@@ -3349,8 +3349,8 @@ static int ext4_iomap_alloc(struct inode *inode, struct ext4_map_blocks *map,
 	 * DAX and direct I/O are the only two operations that are currently
 	 * supported with IOMAP_WRITE.
 	 */
-	WARN_ON(!IS_DAX(inode) && !(flags & IOMAP_DIRECT));
-	if (IS_DAX(inode))
+	WARN_ON(!(flags & (IOMAP_DAX | IOMAP_DIRECT)));
+	if (flags & IOMAP_DAX)
 		m_flags = EXT4_GET_BLOCKS_CREATE_ZERO;
 	/*
 	 * We use i_size instead of i_disksize here because delalloc writeback

fs/xfs/xfs_iomap.c

@@ -188,6 +188,7 @@ xfs_iomap_write_direct(
 	struct xfs_inode	*ip,
 	xfs_fileoff_t		offset_fsb,
 	xfs_fileoff_t		count_fsb,
+	unsigned int		flags,
 	struct xfs_bmbt_irec	*imap)
 {
 	struct xfs_mount	*mp = ip->i_mount;
@@ -229,7 +230,7 @@ xfs_iomap_write_direct(
 	 * the reserve block pool for bmbt block allocation if there is no space
 	 * left but we need to do unwritten extent conversion.
 	 */
-	if (IS_DAX(VFS_I(ip))) {
+	if (flags & IOMAP_DAX) {
 		bmapi_flags = XFS_BMAPI_CONVERT | XFS_BMAPI_ZERO;
 		if (imap->br_state == XFS_EXT_UNWRITTEN) {
 			force = true;
@@ -620,7 +621,7 @@ imap_needs_alloc(
 	    imap->br_startblock == DELAYSTARTBLOCK)
 		return true;
 	/* we convert unwritten extents before copying the data for DAX */
-	if (IS_DAX(inode) && imap->br_state == XFS_EXT_UNWRITTEN)
+	if ((flags & IOMAP_DAX) && imap->br_state == XFS_EXT_UNWRITTEN)
 		return true;
 	return false;
 }
@@ -826,7 +827,7 @@ xfs_direct_write_iomap_begin(
 	xfs_iunlock(ip, lockmode);
 
 	error = xfs_iomap_write_direct(ip, offset_fsb, end_fsb - offset_fsb,
-			&imap);
+			flags, &imap);
 	if (error)
 		return error;
 

fs/xfs/xfs_iomap.h

@@ -12,7 +12,8 @@ struct xfs_inode;
 struct xfs_bmbt_irec;
 
 int xfs_iomap_write_direct(struct xfs_inode *ip, xfs_fileoff_t offset_fsb,
-		xfs_fileoff_t count_fsb, struct xfs_bmbt_irec *imap);
+		xfs_fileoff_t count_fsb, unsigned int flags,
+		struct xfs_bmbt_irec *imap);
 int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t, bool);
 xfs_fileoff_t xfs_iomap_eof_align_last_fsb(struct xfs_inode *ip,
 		xfs_fileoff_t end_fsb);

fs/xfs/xfs_pnfs.c

@@ -155,7 +155,7 @@ xfs_fs_map_blocks(
 		xfs_iunlock(ip, lock_flags);
 
 		error = xfs_iomap_write_direct(ip, offset_fsb,
-				end_fsb - offset_fsb, &imap);
+				end_fsb - offset_fsb, 0, &imap);
 		if (error)
 			goto out_unlock;
 

include/linux/iomap.h

@@ -141,6 +141,11 @@ struct iomap_page_ops {
 #define IOMAP_NOWAIT		(1 << 5) /* do not block */
 #define IOMAP_OVERWRITE_ONLY	(1 << 6) /* only pure overwrites allowed */
 #define IOMAP_UNSHARE		(1 << 7) /* unshare_file_range */
+#ifdef CONFIG_FS_DAX
+#define IOMAP_DAX		(1 << 8) /* DAX mapping */
+#else
+#define IOMAP_DAX		0
+#endif /* CONFIG_FS_DAX */
 
 struct iomap_ops {
 	/*