[PATCH 18/20] Use FIEMAP for FIBMAP calls

[Carlos Maiolino <cmaiolino@redhat.com>]

Enables the usage of FIEMAP ioctl infrastructure to handle FIBMAP calls,
from this point, ->bmap() methods can start to be removed.

Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
---

This patch can be improved, since fiemap_fill_kernel_extent and
fiemap_fill_usr_extent shares a lot of common code, which still is WIP.

 fs/inode.c         | 35 ++++++++++++++++++++++++++++++-----
 fs/ioctl.c         | 31 +++++++++++++++++++++++++++++++
 include/linux/fs.h |  2 ++
 3 files changed, 63 insertions(+), 5 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index d09a6f4f0335..389c2165959c 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1591,11 +1591,36 @@ EXPORT_SYMBOL(iput);
  */
 int bmap(struct inode *inode, sector_t *block)
 {
-	if (!inode->i_mapping->a_ops->bmap)
-		return -EINVAL;
-
-	*block = inode->i_mapping->a_ops->bmap(inode->i_mapping, *block);
-	return 0;
+	struct fiemap_ctx f_ctx;
+	struct fiemap_extent fextent;
+	u64 start = *block << inode->i_blkbits;
+	int error = -EINVAL;
+
+	if (inode->i_op->fiemap) {
+		fextent.fe_logical = 0;
+		fextent.fe_physical = 0;
+		f_ctx.fc_extents_max = 1;
+		f_ctx.fc_extents_mapped = 0;
+		f_ctx.fc_data = &fextent;
+		f_ctx.fc_start = start;
+		f_ctx.fc_len = 1;
+		f_ctx.fc_flags = 0;
+		f_ctx.fc_cb = fiemap_fill_kernel_extent;
+
+		error = inode->i_op->fiemap(inode, &f_ctx);
+
+		if (error)
+			goto out;
+
+		*block = (fextent.fe_physical +
+			(start - fextent.fe_logical)) >> inode->i_blkbits;
+
+	} else if (inode->i_mapping->a_ops->bmap) {
+		*block = inode->i_mapping->a_ops->bmap(inode->i_mapping, *block);
+		error = 0;
+	}
+out:
+	return error;
 }
 EXPORT_SYMBOL(bmap);
 
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 71d11201a06b..dce710699b82 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -113,6 +113,37 @@ int fiemap_fill_usr_extent(struct fiemap_ctx *f_ctx, u64 logical,
 	return (flags & FIEMAP_EXTENT_LAST) ? 1 : 0;
 }
 
+int fiemap_fill_kernel_extent(struct fiemap_ctx *f_ctx, u64 logical,
+			      u64 phys, u64 len, u32 flags)
+{
+	struct fiemap_extent *extent = f_ctx->fc_data;
+
+	if (f_ctx->fc_extents_max == 0) {
+		f_ctx->fc_extents_mapped++;
+		return (flags & FIEMAP_EXTENT_LAST) ? 1 : 0;
+	}
+
+	if (f_ctx->fc_extents_mapped >= f_ctx->fc_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;
+
+	f_ctx->fc_extents_mapped++;
+
+	if (f_ctx->fc_extents_mapped == f_ctx->fc_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 4c6dee908a38..7f623a434cb0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1704,6 +1704,8 @@ struct fiemap_ctx {
 	u64 fc_len;
 };
 
+int fiemap_fill_kernel_extent(struct fiemap_ctx *f_ctx, u64 logical,
+			      u64 phys, u64 len, u32 flags);
 int fiemap_fill_next_extent(struct fiemap_ctx *f_ctx, u64 logical,
 			    u64 phys, u64 len, u32 flags);
 int fiemap_check_flags(struct fiemap_ctx *f_ctx, u32 fs_flags);
-- 
2.17.1