ext4: add new ioctl EXT4_IOC_GET_ES_CACHE

For debugging reasons, it's useful to know the contents of the extent
cache.  Since the extent cache contains much of what is in the fiemap
ioctl, use an fiemap-style interface to return this information.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 86 insertions, 8 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 92266a2da7d6b..0620d495fd8a7 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2315,6 +2315,52 @@ static int ext4_fill_fiemap_extents(struct inode *inode,
 	return err;
 }
 
+static int ext4_fill_es_cache_info(struct inode *inode,
+				   ext4_lblk_t block, ext4_lblk_t num,
+				   struct fiemap_extent_info *fieinfo)
+{
+	ext4_lblk_t next, end = block + num - 1;
+	struct extent_status es;
+	unsigned char blksize_bits = inode->i_sb->s_blocksize_bits;
+	unsigned int flags;
+	int err;
+
+	while (block <= end) {
+		next = 0;
+		flags = 0;
+		if (!ext4_es_lookup_extent(inode, block, &next, &es))
+			break;
+		if (ext4_es_is_unwritten(&es))
+			flags |= FIEMAP_EXTENT_UNWRITTEN;
+		if (ext4_es_is_delayed(&es))
+			flags |= (FIEMAP_EXTENT_DELALLOC |
+				  FIEMAP_EXTENT_UNKNOWN);
+		if (ext4_es_is_hole(&es))
+			flags |= EXT4_FIEMAP_EXTENT_HOLE;
+		if (next == 0)
+			flags |= FIEMAP_EXTENT_LAST;
+		if (flags & (FIEMAP_EXTENT_DELALLOC|
+			     EXT4_FIEMAP_EXTENT_HOLE))
+			es.es_pblk = 0;
+		else
+			es.es_pblk = ext4_es_pblock(&es);
+		err = fiemap_fill_next_extent(fieinfo,
+				(__u64)es.es_lblk << blksize_bits,
+				(__u64)es.es_pblk << blksize_bits,
+				(__u64)es.es_len << blksize_bits,
+				flags);
+		if (next == 0)
+			break;
+		block = next;
+		if (err < 0)
+			return err;
+		if (err == 1)
+			return 0;
+	}
+	return 0;
+}
+
+
 /*
  * ext4_ext_determine_hole - determine hole around given block
  * @inode:	inode we lookup in
@@ -5017,8 +5063,6 @@ static int ext4_find_delayed_extent(struct inode *inode,
 
 	return next_del;
 }
-/* fiemap flags we can handle specified here */
-#define EXT4_FIEMAP_FLAGS	(FIEMAP_FLAG_SYNC|FIEMAP_FLAG_XATTR)
 
 static int ext4_xattr_fiemap(struct inode *inode,
 				struct fiemap_extent_info *fieinfo)
@@ -5055,10 +5099,16 @@ static int ext4_xattr_fiemap(struct inode *inode,
 	return (error < 0 ? error : 0);
 }
 
-int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
-		__u64 start, __u64 len)
+static int _ext4_fiemap(struct inode *inode,
+			struct fiemap_extent_info *fieinfo,
+			__u64 start, __u64 len,
+			int (*fill)(struct inode *, ext4_lblk_t,
+				    ext4_lblk_t,
+				    struct fiemap_extent_info *))
 {
 	ext4_lblk_t start_blk;
+	u32 ext4_fiemap_flags = FIEMAP_FLAG_SYNC|FIEMAP_FLAG_XATTR;
+
 	int error = 0;
 
 	if (ext4_has_inline_data(inode)) {
@@ -5075,14 +5125,18 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		error = ext4_ext_precache(inode);
 		if (error)
 			return error;
+		fieinfo->fi_flags &= ~FIEMAP_FLAG_CACHE;
 	}
 
 	/* fallback to generic here if not in extents fmt */
-	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
+	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) &&
+	    fill == ext4_fill_fiemap_extents)
 		return generic_block_fiemap(inode, fieinfo, start, len,
 			ext4_get_block);
 
-	if (fiemap_check_flags(fieinfo, EXT4_FIEMAP_FLAGS))
+	if (fill == ext4_fill_es_cache_info)
+		ext4_fiemap_flags &= FIEMAP_FLAG_XATTR;
+	if (fiemap_check_flags(fieinfo, ext4_fiemap_flags))
 		return -EBADR;
 
 	if (fieinfo->fi_flags & FIEMAP_FLAG_XATTR) {
@@ -5101,12 +5155,36 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		 * Walk the extent tree gathering extent information
 		 * and pushing extents back to the user.
 		 */
-		error = ext4_fill_fiemap_extents(inode, start_blk,
-						 len_blks, fieinfo);
+		error = fill(inode, start_blk, len_blks, fieinfo);
 	}
 	return error;
 }
 
+int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
+		__u64 start, __u64 len)
+{
+	return _ext4_fiemap(inode, fieinfo, start, len,
+			    ext4_fill_fiemap_extents);
+}
+
+int ext4_get_es_cache(struct inode *inode, struct fiemap_extent_info *fieinfo,
+		      __u64 start, __u64 len)
+{
+	if (ext4_has_inline_data(inode)) {
+		int has_inline;
+
+		down_read(&EXT4_I(inode)->xattr_sem);
+		has_inline = ext4_has_inline_data(inode);
+		up_read(&EXT4_I(inode)->xattr_sem);
+		if (has_inline)
+			return 0;
+	}
+
+	return _ext4_fiemap(inode, fieinfo, start, len,
+			    ext4_fill_es_cache_info);
+}
+
+
 /*
  * ext4_access_path:
  * Function to access the path buffer for marking it dirty.