afs: Do not limit fetches based on vcache length

[openafs.git] / src / afs / afs_dcache.c

diff --git a/src/afs/afs_dcache.c b/src/afs/afs_dcache.c
index 3fc0bb5..be80c7a 100644 (file)
--- a/src/afs/afs_dcache.c
+++ b/src/afs/afs_dcache.c
@@ -2111,6 +2111,32 @@ afs_GetDCache(struct vcache *avc, afs_size_t abyte,
                afs_AdjustSize(tdc, size);      /* changes chunkBytes */
                /* max size for transfer still in size */
            }
+
+           if (size) {
+               /* For the actual fetch, do not limit the request to the
+                * length of the file. If this results in a read past EOF on
+                * the server, the server will just reply with less data than
+                * requested. If we limit ourselves to only requesting data up
+                * to the avc file length, we open ourselves up to races if the
+                * file is extended on the server at about the same time.
+                *
+                * However, we must restrict ourselves to the avc->f.truncPos
+                * length, since this represents an outstanding local
+                * truncation of the file that will be committed to the
+                * fileserver when we actually write the fileserver contents.
+                * If we do not restrict the fetch length based on
+                * avc->f.truncPos, a different truncate operation extending
+                * the file length could cause the old data after
+                * avc->f.truncPos to reappear, instead of extending the file
+                * with NUL bytes. */
+               size = AFS_CHUNKSIZE(abyte);
+               if (Position + size > avc->f.truncPos) {
+                   size = avc->f.truncPos - Position;
+               }
+               if (size < 0) {
+                   size = 0;
+               }
+           }
        }
        if (afs_mariner && !tdc->f.chunk)
            afs_MarinerLog("fetch$Fetching", avc);      /* , Position, size, afs_indexCounter ); */