xfs: xfs_seek_data() refinement with unwritten extents check up from page cache
xfs_seek_data() refinement with unwritten extents check up from page cache.
Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index d78a746..3f91074 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1186,8 +1186,6 @@
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;
@@ -1203,36 +1201,74 @@
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.
*/
+ 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;
+ 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 {
+ /* 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 data extent */
+ if (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.
+ */
+ if (map[i].br_state == XFS_EXT_UNWRITTEN) {
+ if (xfs_find_get_desired_pgoff(inode, &map[i],
+ 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].
+ */
if (nmap == 1) {
error = ENXIO;
goto out_unlock;
}
- offset = max_t(loff_t, start,
- XFS_FSB_TO_B(mp, map[1].br_startoff));
+ ASSERT(i > 1);
+
+ /*
+ * Nothing was found, proceed to the next round of search
+ * if 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) {
+ error = ENXIO;
+ goto out_unlock;
+ }
}
+out:
if (offset != file->f_pos)
file->f_pos = offset;