xfs: combine xfs_seek_hole & xfs_seek_data

xfs_seek_hole & xfs_seek_data are remarkably similar;
so much so that they can be combined, saving a fair
bit of semi-complex code duplication.

The following patch passes generic/285 and generic/286,
which specifically test seek behavior.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 50 insertions, 122 deletions

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 076b1708d134..1da3b7db5bf7 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -964,7 +964,7 @@ xfs_vm_page_mkwrite(
 
 /*
  * This type is designed to indicate the type of offset we would like
- * to search from page cache for either xfs_seek_data() or xfs_seek_hole().
+ * to search from page cache for xfs_seek_hole_data().
  */
 enum {
         HOLE_OFF = 0,
@@ -1021,7 +1021,7 @@ xfs_lookup_buffer_offset(
 /*
  * This routine is called to find out and return a data or hole offset
  * from the page cache for unwritten extents according to the desired
- * type for xfs_seek_data() or xfs_seek_hole().
+ * type for xfs_seek_hole_data().
  *
  * The argument offset is used to tell where we start to search from the
  * page cache.  Map is used to figure out the end points of the range to
@@ -1181,9 +1181,10 @@ out:
 }
 
 STATIC loff_t
-xfs_seek_data(
+xfs_seek_hole_data(
         struct file             *file,
-        loff_t                  start)
+        loff_t                  start,
+        int                     whence)
 {
         struct inode            *inode = file->f_mapping->host;
         struct xfs_inode        *ip = XFS_I(inode);
@@ -1195,6 +1196,9 @@ xfs_seek_data(
         uint                    lock;
         int                     error;
 
+        if (XFS_FORCED_SHUTDOWN(mp))
+                return -EIO;
+
         lock = xfs_ilock_data_map_shared(ip);
 
         isize = i_size_read(inode);
@@ -1209,6 +1213,7 @@ xfs_seek_data(
          */
         fsbno = XFS_B_TO_FSBT(mp, start);
         end = XFS_B_TO_FSB(mp, isize);
+
         for (;;) {
                 struct xfs_bmbt_irec    map[2];
                 int                     nmap = 2;
@@ -1229,29 +1234,48 @@ xfs_seek_data(
                         offset = max_t(loff_t, start,
                                        XFS_FSB_TO_B(mp, map[i].br_startoff));
 
-                        /* Landed in a data extent */
-                        if (map[i].br_startblock == DELAYSTARTBLOCK ||
-                            (map[i].br_state == XFS_EXT_NORM &&
-                             !isnullstartblock(map[i].br_startblock)))
+                        /* Landed in the hole we wanted? */
+                        if (whence == SEEK_HOLE &&
+                            map[i].br_startblock == HOLESTARTBLOCK)
+                                goto out;
+
+                        /* Landed in the data extent we wanted? */
+                        if (whence == SEEK_DATA &&
+                            (map[i].br_startblock == DELAYSTARTBLOCK ||
+                             (map[i].br_state == XFS_EXT_NORM &&
+                              !isnullstartblock(map[i].br_startblock))))
                                 goto out;
 
                         /*
-                         * Landed in an unwritten extent, try to search data
-                         * from page cache.
+                         * Landed in an unwritten extent, try to search
+                         * for hole or data from page cache.
                          */
                         if (map[i].br_state == XFS_EXT_UNWRITTEN) {
                                 if (xfs_find_get_desired_pgoff(inode, &map[i],
-                                                        DATA_OFF, &offset))
+                                      whence == SEEK_HOLE ? HOLE_OFF : DATA_OFF,
+                                                        &offset))
                                         goto out;
                         }
                 }
 
                 /*
-                 * map[0] is hole or its an unwritten extent but
-                 * without data in page cache.  Probably means that
-                 * we are reading after EOF if nothing in map[1].
+                 * We only received one extent out of the two requested. This
+                 * means we've hit EOF and didn't find what we are looking for.
                  */
                 if (nmap == 1) {
+                        /*
+                         * If we were looking for a hole, set offset to
+                         * the end of the file (i.e., there is an implicit
+                         * hole at the end of any file).
+                         */
+                        if (whence == SEEK_HOLE) {
+                                offset = isize;
+                                break;
+                        }
+                        /*
+                         * If we were looking for data, it's nowhere to be found
+                         */
+                        ASSERT(whence == SEEK_DATA);
                         error = -ENXIO;
                         goto out_unlock;
                 }
@@ -1260,125 +1284,30 @@ xfs_seek_data(
 
                 /*
                  * Nothing was found, proceed to the next round of search
-                 * if reading offset not beyond or hit EOF.
+                 * if the next reading offset is not at or beyond EOF.
                  */
                 fsbno = map[i - 1].br_startoff + map[i - 1].br_blockcount;
                 start = XFS_FSB_TO_B(mp, fsbno);
                 if (start >= isize) {
+                        if (whence == SEEK_HOLE) {
+                                offset = isize;
+                                break;
+                        }
+                        ASSERT(whence == SEEK_DATA);
                         error = -ENXIO;
                         goto out_unlock;
                 }
         }
 
 out:
-        offset = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
-
-out_unlock:
-        xfs_iunlock(ip, lock);
-
-        if (error)
-                return error;
-        return offset;
-}
-
-STATIC loff_t
-xfs_seek_hole(
-        struct file             *file,
-        loff_t                  start)
-{
-        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);
-        xfs_fsize_t             isize;
-        xfs_fileoff_t           fsbno;
-        xfs_filblks_t           end;
-        uint                    lock;
-        int                     error;
-
-        if (XFS_FORCED_SHUTDOWN(mp))
-                return -EIO;
-
-        lock = xfs_ilock_data_map_shared(ip);
-
-        isize = i_size_read(inode);
-        if (start >= isize) {
-                error = -ENXIO;
-                goto out_unlock;
-        }
-
-        fsbno = XFS_B_TO_FSBT(mp, start);
-        end = XFS_B_TO_FSB(mp, isize);
-
-        for (;;) {
-                struct xfs_bmbt_irec    map[2];
-                int                     nmap = 2;
-                unsigned int            i;
-
-                error = xfs_bmapi_read(ip, fsbno, end - fsbno, map, &nmap,
-                                       XFS_BMAPI_ENTIRE);
-                if (error)
-                        goto out_unlock;
-
-                /* No extents at given offset, must be beyond EOF */
-                if (nmap == 0) {
-                        error = -ENXIO;
-                        goto out_unlock;
-                }
-
-                for (i = 0; i < nmap; i++) {
-                        offset = max_t(loff_t, start,
-                                       XFS_FSB_TO_B(mp, map[i].br_startoff));
-
-                        /* Landed in a hole */
-                        if (map[i].br_startblock == HOLESTARTBLOCK)
-                                goto out;
-
-                        /*
-                         * Landed in an unwritten extent, try to search hole
-                         * from page cache.
-                         */
-                        if (map[i].br_state == XFS_EXT_UNWRITTEN) {
-                                if (xfs_find_get_desired_pgoff(inode, &map[i],
-                                                        HOLE_OFF, &offset))
-                                        goto out;
-                        }
-                }
-
-                /*
-                 * map[0] contains data or its unwritten but contains
-                 * data in page cache, probably means that we are
-                 * reading after EOF.  We should fix offset to point
-                 * to the end of the file(i.e., there is an implicit
-                 * hole at the end of any file).
-                 */
-                if (nmap == 1) {
-                        offset = isize;
-                        break;
-                }
-
-                ASSERT(i > 1);
-
-                /*
-                 * Both mappings contains data, proceed to the next round of
-                 * search if the current reading offset not beyond or hit EOF.
-                 */
-                fsbno = map[i - 1].br_startoff + map[i - 1].br_blockcount;
-                start = XFS_FSB_TO_B(mp, fsbno);
-                if (start >= isize) {
-                        offset = isize;
-                        break;
-                }
-        }
-
-out:
         /*
-         * At this point, we must have found a hole.  However, the returned
+         * If at this point we have found the hole we wanted, the returned
          * offset may be bigger than the file size as it may be aligned to
-         * page boundary for unwritten extents, we need to deal with this
+         * page boundary for unwritten extents.  We need to deal with this
          * situation in particular.
          */
-        offset = min_t(loff_t, offset, isize);
+        if (whence == SEEK_HOLE)
+                offset = min_t(loff_t, offset, isize);
         offset = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
 
 out_unlock:
@@ -1400,10 +1329,9 @@ xfs_file_llseek(
         case SEEK_CUR:
         case SEEK_SET:
                 return generic_file_llseek(file, offset, origin);
-        case SEEK_DATA:
-                return xfs_seek_data(file, offset);
         case SEEK_HOLE:
-                return xfs_seek_hole(file, offset);
+        case SEEK_DATA:
+                return xfs_seek_hole_data(file, offset, origin);
         default:
                 return -EINVAL;
         }