Search data buffer offset for given range from page cache for unwritten extents.
Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
Reviewed-by: Mark Tinguely <tinguely@xxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
fs/xfs/xfs_file.c | 88 ++++++++++++++++++++++++++++++++++++++++++-----------
1 files changed, 70 insertions(+), 18 deletions(-)
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 43f5e61..15acd4d 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1177,8 +1177,6 @@ xfs_seek_data(
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;
@@ -1194,34 +1192,88 @@ xfs_seek_data(
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;
- 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 {
- if (nmap == 1) {
+ /* No extents at given offset, must be beyond EOF */
+ if (nmap == 0) {
error = ENXIO;
goto out_unlock;
}
offset = max_t(loff_t, start,
- XFS_FSB_TO_B(mp, map[1].br_startoff));
+ XFS_FSB_TO_B(mp, map[0].br_startoff));
+ if (map[0].br_state == XFS_EXT_NORM &&
+ !isnullstartblock(map[0].br_startblock))
+ break;
+ else {
+ /*
+ * Landed in an unwritten extent, try to lookup data
+ * buffer from the page cache before proceeding to
+ * check the next extent map. It's a hole if nothing
+ * was found.
+ */
+ if (map[0].br_startblock == DELAYSTARTBLOCK ||
+ map[0].br_state == XFS_EXT_UNWRITTEN) {
+ /* Probing page cache start from offset */
+ if (xfs_find_get_desired_pgoff(inode, &map[0],
+ DATA_OFF, &offset))
+ break;
+ }
+
+ /*
+ * Found a hole in map[0] and nothing in map[1].
+ * Probably means that we are reading after EOF.
+ */
+ if (nmap == 1) {
+ error = ENXIO;
+ goto out_unlock;
+ }
+
+ /*
+ * We have two mappings, proceed to check map[1].
+ */
+ offset = max_t(loff_t, start,
+ XFS_FSB_TO_B(mp, map[1].br_startoff));
+ if (map[1].br_state == XFS_EXT_NORM &&
+ !isnullstartblock(map[1].br_startblock))
+ break;
+ else {
+ /*
+ * map[1] is also an unwritten extent, lookup
+ * data buffer from page cache now.
+ */
+ if (map[1].br_startblock == DELAYSTARTBLOCK ||
+ map[1].br_state == XFS_EXT_UNWRITTEN) {
+ if (xfs_find_get_desired_pgoff(inode,
+ &map[1], DATA_OFF, &offset))
+ break;
+ }
+ }
+ }
+
+ /*
+ * Nothing was found, proceed to the next round of search if
+ * reading offset not beyond or hit EOF.
+ */
+ fsbno = map[1].br_startoff + map[1].br_blockcount;
+ start = XFS_FSB_TO_B(mp, fsbno);
+ if (start >= isize) {
+ error = ENXIO;
+ goto out_unlock;
+ }
}
if (offset != file->f_pos)
--
1.7.4.1
_______________________________________________
xfs mailing list
xfs@xxxxxxxxxxx
http://oss.sgi.com/mailman/listinfo/xfs
