fs: iomap based fiemap implementation

Add a simple fiemap implementation based on iomap_ops, partially based
on a previous implementation from Bob Peterson <rpeterso@redhat.com>.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

2 files changed, 93 insertions, 0 deletions

diff --git a/fs/iomap.c b/fs/iomap.c
index 477817c00bac..48141b8eff5f 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -405,3 +405,93 @@ out_unlock:
         return ret;
 }
 EXPORT_SYMBOL_GPL(iomap_page_mkwrite);
+
+struct fiemap_ctx {
+        struct fiemap_extent_info *fi;
+        struct iomap prev;
+};
+
+static int iomap_to_fiemap(struct fiemap_extent_info *fi,
+                struct iomap *iomap, u32 flags)
+{
+        switch (iomap->type) {
+        case IOMAP_HOLE:
+                /* skip holes */
+                return 0;
+        case IOMAP_DELALLOC:
+                flags |= FIEMAP_EXTENT_DELALLOC | FIEMAP_EXTENT_UNKNOWN;
+                break;
+        case IOMAP_UNWRITTEN:
+                flags |= FIEMAP_EXTENT_UNWRITTEN;
+                break;
+        case IOMAP_MAPPED:
+                break;
+        }
+
+        return fiemap_fill_next_extent(fi, iomap->offset,
+                        iomap->blkno != IOMAP_NULL_BLOCK ? iomap->blkno << 9: 0,
+                        iomap->length, flags | FIEMAP_EXTENT_MERGED);
+
+}
+
+static loff_t
+iomap_fiemap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
+                struct iomap *iomap)
+{
+        struct fiemap_ctx *ctx = data;
+        loff_t ret = length;
+
+        if (iomap->type == IOMAP_HOLE)
+                return length;
+
+        ret = iomap_to_fiemap(ctx->fi, &ctx->prev, 0);
+        ctx->prev = *iomap;
+        switch (ret) {
+        case 0:         /* success */
+                return length;
+        case 1:         /* extent array full */
+                return 0;
+        default:
+                return ret;
+        }
+}
+
+int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
+                loff_t start, loff_t len, struct iomap_ops *ops)
+{
+        struct fiemap_ctx ctx;
+        loff_t ret;
+
+        memset(&ctx, 0, sizeof(ctx));
+        ctx.fi = fi;
+        ctx.prev.type = IOMAP_HOLE;
+
+        ret = fiemap_check_flags(fi, FIEMAP_FLAG_SYNC);
+        if (ret)
+                return ret;
+
+        ret = filemap_write_and_wait(inode->i_mapping);
+        if (ret)
+                return ret;
+
+        while (len > 0) {
+                ret = iomap_apply(inode, start, len, 0, ops, &ctx,
+                                iomap_fiemap_actor);
+                if (ret < 0)
+                        return ret;
+                if (ret == 0)
+                        break;
+
+                start += ret;
+                len -= ret;
+        }
+
+        if (ctx.prev.type != IOMAP_HOLE) {
+                ret = iomap_to_fiemap(fi, &ctx.prev, FIEMAP_EXTENT_LAST);
+                if (ret < 0)
+                        return ret;
+        }
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(iomap_fiemap);
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index d2f469ae899a..3267df461012 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -3,6 +3,7 @@
 
 #include <linux/types.h>
 
+struct fiemap_extent_info;
 struct inode;
 struct iov_iter;
 struct kiocb;
@@ -63,5 +64,7 @@ int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
                 struct iomap_ops *ops);
 int iomap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
                 struct iomap_ops *ops);
+int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
+                loff_t start, loff_t len, struct iomap_ops *ops);
 
 #endif /* LINUX_IOMAP_H */