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, 72 insertions, 0 deletions

diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index ffb7bde4900d..d6242b7b8718 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -745,6 +745,74 @@ static void ext4_fill_fsxattr(struct inode *inode, struct fsxattr *fa)
 		fa->fsx_projid = from_kprojid(&init_user_ns, ei->i_projid);
 }
 
+/* copied from fs/ioctl.c */
+static int fiemap_check_ranges(struct super_block *sb,
+			       u64 start, u64 len, u64 *new_len)
+{
+	u64 maxbytes = (u64) sb->s_maxbytes;
+
+	*new_len = len;
+
+	if (len == 0)
+		return -EINVAL;
+
+	if (start > maxbytes)
+		return -EFBIG;
+
+	/*
+	 * Shrink request scope to what the fs can actually handle.
+	 */
+	if (len > maxbytes || (maxbytes - len) < start)
+		*new_len = maxbytes - start;
+
+	return 0;
+}
+
+/* So that the fiemap access checks can't overflow on 32 bit machines. */
+#define FIEMAP_MAX_EXTENTS	(UINT_MAX / sizeof(struct fiemap_extent))
+
+static int ext4_ioctl_get_es_cache(struct file *filp, unsigned long arg)
+{
+	struct fiemap fiemap;
+	struct fiemap __user *ufiemap = (struct fiemap __user *) arg;
+	struct fiemap_extent_info fieinfo = { 0, };
+	struct inode *inode = file_inode(filp);
+	struct super_block *sb = inode->i_sb;
+	u64 len;
+	int error;
+
+	if (copy_from_user(&fiemap, ufiemap, sizeof(fiemap)))
+		return -EFAULT;
+
+	if (fiemap.fm_extent_count > FIEMAP_MAX_EXTENTS)
+		return -EINVAL;
+
+	error = fiemap_check_ranges(sb, fiemap.fm_start, fiemap.fm_length,
+				    &len);
+	if (error)
+		return error;
+
+	fieinfo.fi_flags = fiemap.fm_flags;
+	fieinfo.fi_extents_max = fiemap.fm_extent_count;
+	fieinfo.fi_extents_start = ufiemap->fm_extents;
+
+	if (fiemap.fm_extent_count != 0 &&
+	    !access_ok(fieinfo.fi_extents_start,
+		       fieinfo.fi_extents_max * sizeof(struct fiemap_extent)))
+		return -EFAULT;
+
+	if (fieinfo.fi_flags & FIEMAP_FLAG_SYNC)
+		filemap_write_and_wait(inode->i_mapping);
+
+	error = ext4_get_es_cache(inode, &fieinfo, fiemap.fm_start, len);
+	fiemap.fm_flags = fieinfo.fi_flags;
+	fiemap.fm_mapped_extents = fieinfo.fi_extents_mapped;
+	if (copy_to_user(ufiemap, &fiemap, sizeof(fiemap)))
+		error = -EFAULT;
+
+	return error;
+}
+
 long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	struct inode *inode = file_inode(filp);
@@ -1139,6 +1207,9 @@ resizefs_out:
 		return put_user(state, (__u32 __user *) arg);
 	}
 
+	case EXT4_IOC_GET_ES_CACHE:
+		return ext4_ioctl_get_es_cache(filp, arg);
+
 	case EXT4_IOC_FSGETXATTR:
 	{
 		struct fsxattr fa;
@@ -1259,6 +1330,7 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case FS_IOC_GETFSMAP:
 	case EXT4_IOC_CLEAR_ES_CACHE:
 	case EXT4_IOC_GETSTATE:
+	case EXT4_IOC_GET_ES_CACHE:
 		break;
 	default:
 		return -ENOIOCTLCMD;