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>

1 files changed, 142 insertions, 1 deletions

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 51fc2cf07d5e..8d214b87f6bb 100644
--- 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,