[PATCH 09/10 V2] Use FIEMAP for FIBMAP calls

[Carlos Maiolino <cmaiolino@xxxxxxxxxx>]

Enables the usage of FIEMAP ioctl infrastructure to handle FIBMAP calls.
>From now on, ->bmap() methods can start to be removed from filesystems
which already provides ->fiemap().

This adds a new helper - bmap_fiemap() - which is used to fill in the
fiemap request, call into the underlying filesystem and check the flags
set in the extent requested.

Add a new fiemap fill extent callback to handl the in-kernel only
fiemap_extent structure used for FIBMAP.

V2:
	- Now based on the updated fiemap_extent_info,
	- move the fiemap call itself to a new helper

Signed-off-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
---
 fs/inode.c         | 42 ++++++++++++++++++++++++++++++++++++++++--
 fs/ioctl.c         | 32 ++++++++++++++++++++++++++++++++
 include/linux/fs.h |  2 ++
 3 files changed, 74 insertions(+), 2 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index db681d310465..f07cc183ddbd 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1578,6 +1578,40 @@ void iput(struct inode *inode)
 }
 EXPORT_SYMBOL(iput);
 
+static int bmap_fiemap(struct inode *inode, sector_t *block)
+{
+	struct fiemap_extent_info fieinfo = { 0, };
+	struct fiemap_extent fextent;
+	u64 start = *block << inode->i_blkbits;
+	int error = -EINVAL;
+
+	fextent.fe_logical = 0;
+	fextent.fe_physical = 0;
+	fieinfo.fi_extents_max = 1;
+	fieinfo.fi_extents_mapped = 0;
+	fieinfo.fi_extents_start = &fextent;
+	fieinfo.fi_start = start;
+	fieinfo.fi_len = 1 << inode->i_blkbits;
+	fieinfo.fi_flags = 0;
+	fieinfo.fi_cb = fiemap_fill_kernel_extent;
+
+	error = inode->i_op->fiemap(inode, &fieinfo);
+
+	if (error)
+		return error;
+
+	if (fieinfo.fi_flags & (FIEMAP_EXTENT_UNKNOWN |
+				FIEMAP_EXTENT_ENCODED |
+				FIEMAP_EXTENT_DATA_INLINE |
+				FIEMAP_EXTENT_UNWRITTEN))
+		return -EINVAL;
+
+	*block = (fextent.fe_physical +
+		  (start - fextent.fe_logical)) >> inode->i_blkbits;
+
+	return error;
+}
+
 /**
  *	bmap	- find a block number in a file
  *	@inode:  inode owning the block number being requested
@@ -1594,10 +1628,14 @@ EXPORT_SYMBOL(iput);
  */
 int bmap(struct inode *inode, sector_t *block)
 {
-	if (!inode->i_mapping->a_ops->bmap)
+	if (inode->i_op->fiemap)
+		return bmap_fiemap(inode, block);
+	else if (inode->i_mapping->a_ops->bmap)
+		*block = inode->i_mapping->a_ops->bmap(inode->i_mapping,
+						       *block);
+	else
 		return -EINVAL;
 
-	*block = inode->i_mapping->a_ops->bmap(inode->i_mapping, *block);
 	return 0;
 }
 EXPORT_SYMBOL(bmap);
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 6086978fe01e..bfa59df332bf 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -116,6 +116,38 @@ int fiemap_fill_user_extent(struct fiemap_extent_info *fieinfo, u64 logical,
 	return (flags & FIEMAP_EXTENT_LAST) ? 1 : 0;
 }
 
+int fiemap_fill_kernel_extent(struct fiemap_extent_info *fieinfo, u64 logical,
+			    u64 phys, u64 len, u32 flags)
+{
+	struct fiemap_extent *extent = fieinfo->fi_extents_start;
+
+	/* only count the extents */
+	if (fieinfo->fi_extents_max == 0) {
+		fieinfo->fi_extents_mapped++;
+		return (flags & FIEMAP_EXTENT_LAST) ? 1 : 0;
+	}
+
+	if (fieinfo->fi_extents_mapped >= fieinfo->fi_extents_max)
+		return 1;
+
+	if (flags & SET_UNKNOWN_FLAGS)
+		flags |= FIEMAP_EXTENT_UNKNOWN;
+	if (flags & SET_NO_UNMOUNTED_IO_FLAGS)
+		flags |= FIEMAP_EXTENT_ENCODED;
+	if (flags & SET_NOT_ALIGNED_FLAGS)
+		flags |= FIEMAP_EXTENT_NOT_ALIGNED;
+
+	extent->fe_logical = logical;
+	extent->fe_physical = phys;
+	extent->fe_length = len;
+	extent->fe_flags = flags;
+
+	fieinfo->fi_extents_mapped++;
+
+	if (fieinfo->fi_extents_mapped == fieinfo->fi_extents_max)
+		return 1;
+	return (flags & FIEMAP_EXTENT_LAST) ? 1 : 0;
+}
 /**
  * fiemap_fill_next_extent - Fiemap helper function
  * @fieinfo:	Fiemap context passed into ->fiemap
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7a434979201c..28bb523d532a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1711,6 +1711,8 @@ struct fiemap_extent_info {
 	fiemap_fill_cb	fi_cb;
 };
 
+int fiemap_fill_kernel_extent(struct fiemap_extent_info *info, u64 logical,
+			      u64 phys, u64 len, u32 flags);
 int fiemap_fill_next_extent(struct fiemap_extent_info *info, u64 logical,
 			    u64 phys, u64 len, u32 flags);
 int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags);
-- 
2.17.2