xfs: introduce SEEK_DATA/SEEK_HOLE support

This patch adds lseek(2) SEEK_DATA/SEEK_HOLE functionality to xfs.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 51fc2cf07d5e42633f7a4273c837fb15bfe430ed..8d214b87f6bb06ed1f7ed204cdfda8da9345172f 100644 (file)
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -963,8 +963,149 @@ xfs_vm_page_mkwrite(
        return block_page_mkwrite(vma, vmf, xfs_get_blocks);
 }
 
+STATIC loff_t
+xfs_seek_data(
+       struct file             *file,
+       loff_t                  start,
+       u32                     type)
+{
+       struct inode            *inode = file->f_mapping->host;
+       struct xfs_inode        *ip = XFS_I(inode);
+       struct xfs_mount        *mp = ip->i_mount;
+       struct xfs_bmbt_irec    map[2];
+       int                     nmap = 2;
+       loff_t                  uninitialized_var(offset);
+       xfs_fsize_t             isize;
+       xfs_fileoff_t           fsbno;
+       xfs_filblks_t           end;
+       uint                    lock;
+       int                     error;
+
+       lock = xfs_ilock_map_shared(ip);
+
+       isize = i_size_read(inode);
+       if (start >= isize) {
+               error = ENXIO;
+               goto out_unlock;
+       }
+
+       fsbno = XFS_B_TO_FSBT(mp, start);
+
+       /*
+        * Try to read extents from the first block indicated
+        * by fsbno to the end block of the file.
+        */
+       end = XFS_B_TO_FSB(mp, isize);
+
+       error = xfs_bmapi_read(ip, fsbno, end - fsbno, map, &nmap,
+                              XFS_BMAPI_ENTIRE);
+       if (error)
+               goto out_unlock;
+
+       /*
+        * Treat unwritten extent as data extent since it might
+        * contains dirty data in page cache.
+        */
+       if (map[0].br_startblock != HOLESTARTBLOCK) {
+               offset = max_t(loff_t, start,
+                              XFS_FSB_TO_B(mp, map[0].br_startoff));
+       } else {
+               if (nmap == 1) {
+                       error = ENXIO;
+                       goto out_unlock;
+               }
+
+               offset = max_t(loff_t, start,
+                              XFS_FSB_TO_B(mp, map[1].br_startoff));
+       }
+
+       if (offset != file->f_pos)
+               file->f_pos = offset;
+
+out_unlock:
+       xfs_iunlock_map_shared(ip, lock);
+
+       if (error)
+               return -error;
+       return offset;
+}
+
+STATIC loff_t
+xfs_seek_hole(
+       struct file             *file,
+       loff_t                  start,
+       u32                     type)
+{
+       struct inode            *inode = file->f_mapping->host;
+       struct xfs_inode        *ip = XFS_I(inode);
+       struct xfs_mount        *mp = ip->i_mount;
+       loff_t                  uninitialized_var(offset);
+       loff_t                  holeoff;
+       xfs_fsize_t             isize;
+       xfs_fileoff_t           fsbno;
+       uint                    lock;
+       int                     error;
+
+       if (XFS_FORCED_SHUTDOWN(mp))
+               return -XFS_ERROR(EIO);
+
+       lock = xfs_ilock_map_shared(ip);
+
+       isize = i_size_read(inode);
+       if (start >= isize) {
+               error = ENXIO;
+               goto out_unlock;
+       }
+
+       fsbno = XFS_B_TO_FSBT(mp, start);
+       error = xfs_bmap_first_unused(NULL, ip, 1, &fsbno, XFS_DATA_FORK);
+       if (error)
+               goto out_unlock;
+
+       holeoff = XFS_FSB_TO_B(mp, fsbno);
+       if (holeoff <= start)
+               offset = start;
+       else {
+               /*
+                * xfs_bmap_first_unused() could return a value bigger than
+                * isize if there are no more holes past the supplied offset.
+                */
+               offset = min_t(loff_t, holeoff, isize);
+       }
+
+       if (offset != file->f_pos)
+               file->f_pos = offset;
+
+out_unlock:
+       xfs_iunlock_map_shared(ip, lock);
+
+       if (error)
+               return -error;
+       return offset;
+}
+
+STATIC loff_t
+xfs_file_llseek(
+       struct file     *file,
+       loff_t          offset,
+       int             origin)
+{
+       switch (origin) {
+       case SEEK_END:
+       case SEEK_CUR:
+       case SEEK_SET:
+               return generic_file_llseek(file, offset, origin);
+       case SEEK_DATA:
+               return xfs_seek_data(file, offset, origin);
+       case SEEK_HOLE:
+               return xfs_seek_hole(file, offset, origin);
+       default:
+               return -EINVAL;
+       }
+}
+
 const struct file_operations xfs_file_operations = {
-       .llseek         = generic_file_llseek,
+       .llseek         = xfs_file_llseek,
        .read           = do_sync_read,
        .write          = do_sync_write,
        .aio_read       = xfs_file_aio_read,