vfs: vfs-level fiemap interface

Basic vfs-level fiemap infrastructure, which sets up a new ->fiemap
inode operation.

Userspace can get extent information on a file via fiemap ioctl. As input,
the fiemap ioctl takes a struct fiemap which includes an array of struct
fiemap_extent (fm_extents). Size of the extent array is passed as
fm_extent_count and number of extents returned will be written into
fm_mapped_extents. Offset and length fields on the fiemap structure
(fm_start, fm_length) describe a logical range which will be searched for
extents. All extents returned will at least partially contain this range.
The actual extent offsets and ranges returned will be unmodified from their
offset and range on-disk.

The fiemap ioctl returns '0' on success. On error, -1 is returned and errno
is set. If errno is equal to EBADR, then fm_flags will contain those flags
which were passed in which the kernel did not understand. On all other
errors, the contents of fm_extents is undefined.

As fiemap evolved, there have been many authors of the vfs patch. As far as
I can tell, the list includes:
Kalpak Shah <kalpak.shah@sun.com>
Andreas Dilger <adilger@sun.com>
Eric Sandeen <sandeen@redhat.com>
Mark Fasheh <mfasheh@suse.com>

Signed-off-by: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: linux-api@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org

1 files changed, 18 insertions, 0 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 580b513668fe..194fb237a307 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -231,6 +231,7 @@ extern int dir_notify_enable;
 #define FS_IOC_SETFLAGS                 _IOW('f', 2, long)
 #define FS_IOC_GETVERSION               _IOR('v', 1, long)
 #define FS_IOC_SETVERSION               _IOW('v', 2, long)
+#define FS_IOC_FIEMAP                   _IOWR('f', 11, struct fiemap)
 #define FS_IOC32_GETFLAGS               _IOR('f', 1, int)
 #define FS_IOC32_SETFLAGS               _IOW('f', 2, int)
 #define FS_IOC32_GETVERSION             _IOR('v', 1, int)
@@ -291,6 +292,7 @@ extern int dir_notify_enable;
 #include <linux/mutex.h>
 #include <linux/capability.h>
 #include <linux/semaphore.h>
+#include <linux/fiemap.h>
 
 #include <asm/atomic.h>
 #include <asm/byteorder.h>
@@ -1179,6 +1181,20 @@ extern void dentry_unhash(struct dentry *dentry);
 extern int file_permission(struct file *, int);
 
 /*
+ * VFS FS_IOC_FIEMAP helper definitions.
+ */
+struct fiemap_extent_info {
+        unsigned int fi_flags;          /* Flags as passed from user */
+        unsigned int fi_extents_mapped; /* Number of mapped extents */
+        unsigned int fi_extents_max;    /* Size of fiemap_extent array */
+        struct fiemap_extent *fi_extents_start; /* Start of fiemap_extent
+                                                 * array */
+};
+int fiemap_fill_next_extent(struct fiemap_extent_info *info, u64 logical,
+                            u64 phys, u64 len, u32 flags);
+int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags);
+
+/*
  * File types
  *
  * NOTE! These match bits 12..15 of stat.st_mode
@@ -1287,6 +1303,8 @@ struct inode_operations {
         void (*truncate_range)(struct inode *, loff_t, loff_t);
         long (*fallocate)(struct inode *inode, int mode, loff_t offset,
                           loff_t len);
+        int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
+                      u64 len);
 };
 
 struct seq_file;