Btrfs: fiemap support

Now that bmap support is gone, this is the only way to get extent
mappings for userland.  These are still not valid for IO, but they
can tell us if a file has holes or how much fragmentation there is.

Signed-off-by: Yehuda Sadeh <yehuda@hq.newdream.net>

3 files changed, 101 insertions, 0 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index c9446d4840ed..a3b0676403f7 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2854,6 +2854,98 @@ out:
         return sector;
 }
 
+int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
+                __u64 start, __u64 len, get_extent_t *get_extent)
+{
+        int ret;
+        u64 off = start;
+        u64 max = start + len;
+        u32 flags = 0;
+        u64 disko = 0;
+        struct extent_map *em = NULL;
+        int end = 0;
+        u64 em_start = 0, em_len = 0;
+        unsigned long emflags;
+        ret = 0;
+
+        if (len == 0)
+                return -EINVAL;
+
+        lock_extent(&BTRFS_I(inode)->io_tree, start, start + len,
+                GFP_NOFS);
+        em = get_extent(inode, NULL, 0, off, max - off, 0);
+        if (!em)
+                goto out;
+        if (IS_ERR(em)) {
+                ret = PTR_ERR(em);
+                goto out;
+        }
+        while (!end) {
+                off = em->start + em->len;
+                if (off >= max)
+                        end = 1;
+
+                em_start = em->start;
+                em_len = em->len;
+
+                disko = 0;
+                flags = 0;
+
+                switch (em->block_start) {
+                case EXTENT_MAP_LAST_BYTE:
+                        end = 1;
+                        flags |= FIEMAP_EXTENT_LAST;
+                        break;
+                case EXTENT_MAP_HOLE:
+                        flags |= FIEMAP_EXTENT_UNWRITTEN;
+                        break;
+                case EXTENT_MAP_INLINE:
+                        flags |= (FIEMAP_EXTENT_DATA_INLINE |
+                                  FIEMAP_EXTENT_NOT_ALIGNED);
+                        break;
+                case EXTENT_MAP_DELALLOC:
+                        flags |= (FIEMAP_EXTENT_DELALLOC |
+                                  FIEMAP_EXTENT_UNKNOWN);
+                        break;
+                default:
+                        disko = em->block_start;
+                        break;
+                }
+                if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
+                        flags |= FIEMAP_EXTENT_ENCODED;
+
+                emflags = em->flags;
+                free_extent_map(em);
+                em = NULL;
+
+                if (!end) {
+                        em = get_extent(inode, NULL, 0, off, max - off, 0);
+                        if (!em)
+                                goto out;
+                        if (IS_ERR(em)) {
+                                ret = PTR_ERR(em);
+                                goto out;
+                        }
+                        emflags = em->flags;
+                }
+                if (test_bit(EXTENT_FLAG_VACANCY, &emflags)) {
+                        flags |= FIEMAP_EXTENT_LAST;
+                        end = 1;
+                }
+
+                ret = fiemap_fill_next_extent(fieinfo, em_start, disko,
+                                        em_len, flags);
+                if (ret)
+                        goto out_free;
+        }
+out_free:
+        free_extent_map(em);
+out:
+        unlock_extent(&BTRFS_I(inode)->io_tree, start, start + len,
+                        GFP_NOFS);
+        return ret;
+}
+
 static inline struct page *extent_buffer_page(struct extent_buffer *eb,
                                               unsigned long i)
 {
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index c5b483a79137..e80c6d96b318 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -193,6 +193,8 @@ int extent_commit_write(struct extent_io_tree *tree,
                         unsigned from, unsigned to);
 sector_t extent_bmap(struct address_space *mapping, sector_t iblock,
                 get_extent_t *get_extent);
+int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
+                __u64 start, __u64 len, get_extent_t *get_extent);
 int set_range_dirty(struct extent_io_tree *tree, u64 start, u64 end);
 int set_state_private(struct extent_io_tree *tree, u64 start, u64 private);
 int get_state_private(struct extent_io_tree *tree, u64 start, u64 *private);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 2e25d698bab0..288c2cdc7543 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4156,6 +4156,12 @@ static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
         return -EINVAL;
 }
 
+static int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
+                __u64 start, __u64 len)
+{
+        return extent_fiemap(inode, fieinfo, start, len, btrfs_get_extent);
+}
+
 int btrfs_readpage(struct file *file, struct page *page)
 {
         struct extent_io_tree *tree;
@@ -5021,6 +5027,7 @@ static struct inode_operations btrfs_file_inode_operations = {
         .removexattr    = btrfs_removexattr,
         .permission     = btrfs_permission,
         .fallocate      = btrfs_fallocate,
+        .fiemap         = btrfs_fiemap,
 };
 static struct inode_operations btrfs_special_inode_operations = {
         .getattr        = btrfs_getattr,