Linux: Fix tmpfs cache support

As of kernel 3.1, tmpfs no longer has a readpage() operation in its
address space operations.  Some of the cache manager code relies on
this, causing an oops if tmpfs is used as backing store for the
cache.

As a minimal fix, detect that there is no readpage() and disable
the optimizations that depend on it.

Reviewed-on: http://gerrit.openafs.org/9949
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit 3767cf8bf420bd59c3426a4287259b1e97178e96)

Reviewed-on: http://gerrit.openafs.org/9950
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
(cherry picked from commit 7a40c83337cb4ff07646ea7c2cc0d6d98be94bff)

Change-Id: I063428ba5a177b57eccf883c2019dbc670a6c080
Reviewed-on: http://gerrit.openafs.org/10612
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: Stephan Wiesand <stephan.wiesand@desy.de>

diff --git a/src/afs/LINUX/osi_vnodeops.c b/src/afs/LINUX/osi_vnodeops.c
index 3a2a67f6b486a6015f9bcd04bdf1be4603a25297..d1a62bb4a957472c2a16d5ee01adac36fb50ba0e 100644 (file)
--- a/src/afs/LINUX/osi_vnodeops.c
+++ b/src/afs/LINUX/osi_vnodeops.c
@@ -47,6 +47,8 @@
 #define MAX_ERRNO 1000L
 #endif
 
+int cachefs_noreadpage = 0;
+
 extern struct backing_dev_info *afs_backing_dev_info;
 
 extern struct vcache *afs_globalVp;
@@ -1877,6 +1879,10 @@ afs_linux_readpage_fastpath(struct file *fp, struct page *pp, int *codep)
     if (cacheDiskType != AFS_FCACHE_TYPE_UFS)
        return 0;
 
+    /* No readpage (ex: tmpfs) , skip */
+    if (cachefs_noreadpage)
+       return 0;
+
     /* Can't do anything if the vcache isn't statd , or if the read
      * crosses a chunk boundary.
      */
@@ -1936,12 +1942,8 @@ afs_linux_readpage_fastpath(struct file *fp, struct page *pp, int *codep)
 
     /* Is the dcache we've been given currently up to date */
     if (!hsame(avc->f.m.DataVersion, tdc->f.versionNo) ||
-       (tdc->dflags & DFFetching)) {
-       ReleaseWriteLock(&avc->lock);
-       ReleaseReadLock(&tdc->lock);
-       afs_PutDCache(tdc);
-       return 0;
-    }
+       (tdc->dflags & DFFetching))
+       goto out;
 
     /* Update our hint for future abuse */
     avc->dchint = tdc;
@@ -1951,6 +1953,11 @@ afs_linux_readpage_fastpath(struct file *fp, struct page *pp, int *codep)
     /* XXX - I suspect we should be locking the inodes before we use them! */
     AFS_GUNLOCK();
     cacheFp = afs_linux_raw_open(&tdc->f.inode);
+    if (!cacheFp->f_dentry->d_inode->i_mapping->a_ops->readpage) {
+       cachefs_noreadpage = 1;
+       AFS_GLOCK();
+       goto out;
+    }
     pagevec_init(&lrupv, 0);
 
     code = afs_linux_read_cache(cacheFp, pp, tdc->f.chunk, &lrupv, NULL);
@@ -1967,6 +1974,12 @@ afs_linux_readpage_fastpath(struct file *fp, struct page *pp, int *codep)
 
     *codep = code;
     return 1;
+
+out:
+    ReleaseWriteLock(&avc->lock);
+    ReleaseReadLock(&tdc->lock);
+    afs_PutDCache(tdc);
+    return 0;
 }
 
 /* afs_linux_readpage
@@ -2308,6 +2321,10 @@ afs_linux_readpages(struct file *fp, struct address_space *mapping,
     if (cacheDiskType == AFS_FCACHE_TYPE_MEM)
        return 0;
 
+    /* No readpage (ex: tmpfs) , skip */
+    if (cachefs_noreadpage)
+       return 0;
+
     AFS_GLOCK();
     if ((code = afs_linux_VerifyVCache(avc, NULL))) {
        AFS_GUNLOCK();
@@ -2342,14 +2359,20 @@ afs_linux_readpages(struct file *fp, struct address_space *mapping,
                ObtainReadLock(&tdc->lock);
                if (!hsame(avc->f.m.DataVersion, tdc->f.versionNo) ||
                    (tdc->dflags & DFFetching)) {
+                   goto out;
                    ReleaseReadLock(&tdc->lock);
                    afs_PutDCache(tdc);
                    tdc = NULL;
                }
            }
            AFS_GUNLOCK();
-           if (tdc)
+           if (tdc) {
                cacheFp = afs_linux_raw_open(&tdc->f.inode);
+               if (!cacheFp->f_dentry->d_inode->i_mapping->a_ops->readpage) {
+                   cachefs_noreadpage = 1;
+                   goto out;
+               }
+           }
        }
 
        if (tdc && !add_to_page_cache(page, mapping, page->index,
@@ -2365,6 +2388,7 @@ afs_linux_readpages(struct file *fp, struct address_space *mapping,
     if (pagevec_count(&lrupv))
        __pagevec_lru_add_file(&lrupv);
 
+out:
     if (tdc)
        filp_close(cacheFp, NULL);