SOLARIS: Granular multiPage detection

[openafs.git] / src / afs / SOLARIS / osi_vnodeops.c

diff --git a/src/afs/SOLARIS/osi_vnodeops.c b/src/afs/SOLARIS/osi_vnodeops.c
index 514294e..b0076ec 100644 (file)
--- a/src/afs/SOLARIS/osi_vnodeops.c
+++ b/src/afs/SOLARIS/osi_vnodeops.c
@@ -158,14 +158,39 @@ afs_getpage(struct vnode *vp, offset_t off, u_int len, u_int *protp,
        code =
            afs_GetOnePage(vp, off, len, protp, pl, plsz, seg, addr, rw, acred);
     else {
+       struct multiPage_range range;
        struct vcache *vcp = VTOAFS(vp);
+
+       /* We've been asked to get more than one page. We must return all
+        * requested pages at once, all of them locked, which means all of
+        * these dcache entries cannot be kicked out of the cache before we
+        * return (since their pages cannot be invalidated).
+        *
+        * afs_GetOnePage will be called multiple times by pvn_getpages in
+        * order to get all of the requested pages. One of the later
+        * afs_GetOnePage calls may need to evict some cache entries in order
+        * to perform its read. If we try to kick out one of the entries an
+        * earlier afs_GetOnePage call used, we will deadlock since we have
+        * the page locked. So, to tell afs_GetDownD that it should skip over
+        * any entries we've read in due to this afs_getpage call, record the
+        * offset and length in avc->multiPage.
+        *
+        * Ideally we would just set something in each dcache as we get it,
+        * but that is rather difficult, since pvn_getpages doesn't let us
+        * retain any information between calls to afs_GetOnePage. So instead
+        * just record the offset and length, and let afs_GetDownD calculate
+        * which dcache entries should be skipped. */
+
+       range.off = off;
+       range.len = len;
+
        ObtainWriteLock(&vcp->vlock, 548);
-       vcp->multiPage++;
+       QAdd(&vcp->multiPage, &range.q);
        ReleaseWriteLock(&vcp->vlock);
        code =
            pvn_getpages(afs_GetOnePage, vp, off, len, protp, pl, plsz, seg, addr, rw, acred);
        ObtainWriteLock(&vcp->vlock, 549);
-       vcp->multiPage--;
+       QRemove(&range.q);
        ReleaseWriteLock(&vcp->vlock);
     }
     AFS_GUNLOCK();