afs: Handle easy GetValidDSlot errors

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

diff --git a/src/afs/afs_dcache.c b/src/afs/afs_dcache.c
index 647f912..388a413 100644 (file)
--- a/src/afs/afs_dcache.c
+++ b/src/afs/afs_dcache.c
@@ -1315,7 +1315,12 @@ afs_TryToSmush(struct vcache *avc, afs_ucred_t *acred, int sync)
        if (afs_indexUnique[index] == avc->f.fid.Fid.Unique) {
            int releaseTlock = 1;
            tdc = afs_GetValidDSlot(index);
-           if (!tdc) osi_Panic("afs_TryToSmush tdc");
+           if (!tdc) {
+               /* afs_TryToSmush is best-effort; we may not actually discard
+                * everything, so failure to discard a dcache due to an i/o
+                * error is okay. */
+               continue;
+           }
            if (!FidCmp(&tdc->f.fid, &avc->f.fid)) {
                if (sync) {
                    if ((afs_indexFlags[index] & IFDataMod) == 0
@@ -1457,17 +1462,21 @@ afs_FindDCache(struct vcache *avc, afs_size_t abyte)
      */
     i = DCHash(&avc->f.fid, chunk);
     ObtainWriteLock(&afs_xdcache, 278);
-    for (index = afs_dchashTbl[i]; index != NULLIDX;) {
+    for (index = afs_dchashTbl[i]; index != NULLIDX; index = afs_dcnextTbl[index]) {
        if (afs_indexUnique[index] == avc->f.fid.Fid.Unique) {
            tdc = afs_GetValidDSlot(index);
-           if (!tdc) osi_Panic("afs_FindDCache tdc");
+           if (!tdc) {
+               /* afs_FindDCache is best-effort; we may not find the given
+                * file/offset, so if we cannot find the given dcache due to
+                * i/o errors, that is okay. */
+               continue;
+           }
            ReleaseReadLock(&tdc->tlock);
            if (!FidCmp(&tdc->f.fid, &avc->f.fid) && chunk == tdc->f.chunk) {
                break;          /* leaving refCount high for caller */
            }
            afs_PutDCache(tdc);
        }
-       index = afs_dcnextTbl[index];
     }
     if (index != NULLIDX) {
        hset(afs_indexTimes[tdc->index], afs_indexCounter);
@@ -1758,6 +1767,7 @@ afs_GetDCache(struct vcache *avc, afs_size_t abyte,
      */
 
     if (!tdc) {                        /* If the hint wasn't the right dcache entry */
+       int dslot_error = 0;
        /*
         * Hash on the [fid, chunk] and get the corresponding dcache index
         * after write-locking the dcache.
@@ -1775,12 +1785,16 @@ afs_GetDCache(struct vcache *avc, afs_size_t abyte,
 
        ObtainWriteLock(&afs_xdcache, 280);
        us = NULLIDX;
-       for (index = afs_dchashTbl[i]; index != NULLIDX;) {
+       for (index = afs_dchashTbl[i]; index != NULLIDX; us = index, index = afs_dcnextTbl[index]) {
            if (afs_indexUnique[index] == avc->f.fid.Fid.Unique) {
                tdc = afs_GetValidDSlot(index);
                if (!tdc) {
-                   ReleaseWriteLock(&afs_xdcache);
-                   goto done;
+                   /* we got an i/o error when trying to get the given dslot,
+                    * but do not bail out just yet; it is possible the dcache
+                    * we're looking for is elsewhere, so it doesn't matter if
+                    * we can't load this one. */
+                   dslot_error = 1;
+                   continue;
                }
                ReleaseReadLock(&tdc->tlock);
                /*
@@ -1803,8 +1817,6 @@ afs_GetDCache(struct vcache *avc, afs_size_t abyte,
                afs_PutDCache(tdc);
                tdc = 0;
            }
-           us = index;
-           index = afs_dcnextTbl[index];
        }
 
        /*
@@ -1820,6 +1832,16 @@ afs_GetDCache(struct vcache *avc, afs_size_t abyte,
            afs_Trace2(afs_iclSetp, CM_TRACE_GETDCACHE1, ICL_TYPE_POINTER,
                       avc, ICL_TYPE_INT32, chunk);
 
+           if (dslot_error) {
+               /* We couldn't find the dcache we want, but we hit some i/o
+                * errors when trying to find it, so we're not sure if the
+                * dcache we want is in the cache or not. Error out, so we
+                * don't try to possibly create 2 separate dcaches for the
+                * same exact data. */
+               ReleaseWriteLock(&afs_xdcache);
+               goto done;
+           }
+
            /* Make sure there is a free dcache entry for us to use */
            if (afs_discardDCList == NULLIDX && afs_freeDCList == NULLIDX) {
                while (1) {