xfs
[Top] [All Lists]

[PATCH v5 3/4]xfs: xfs_seek_data() refinements with lookup data buffer o

To: xfs@xxxxxxxxxxx
Subject: [PATCH v5 3/4]xfs: xfs_seek_data() refinements with lookup data buffer offset from page cache.
From: Jeff Liu <jeff.liu@xxxxxxxxxx>
Date: Thu, 26 Jul 2012 23:32:50 +0800
In-reply-to: <50110630.7020902@xxxxxxxxxx>
Organization: Oracle
References: <50110630.7020902@xxxxxxxxxx>
Reply-to: jeff.liu@xxxxxxxxxx
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.28) Gecko/20120313 Thunderbird/3.1.20
Search data buffer offset for given range from page cache.

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 69965a4..b1158b3 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1182,8 +1182,6 @@ 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;
@@ -1199,34 +1197,88 @@ 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

<Prev in Thread] Current Thread [Next in Thread>