ceph: try getting buffer capability for readahead/fadvise

For readahead/fadvise cases, caller of ceph_readpages does not
hold buffer capability. Pages can be added to page cache while
there is no buffer capability. This can cause data integrity
issue.

Signed-off-by: Yan, Zheng <zyan@redhat.com>

4 files changed, 73 insertions, 11 deletions

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index ef3ebd780aff..dbb5f7d69216 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -315,7 +315,32 @@ static int start_read(struct inode *inode, struct list_head *page_list, int max)
         struct page **pages;
         pgoff_t next_index;
         int nr_pages = 0;
-        int ret;
+        int got = 0;
+        int ret = 0;
+
+        if (!current->journal_info) {
+                /* caller of readpages does not hold buffer and read caps
+                 * (fadvise, madvise and readahead cases) */
+                int want = CEPH_CAP_FILE_CACHE;
+                ret = ceph_try_get_caps(ci, CEPH_CAP_FILE_RD, want, &got);
+                if (ret < 0) {
+                        dout("start_read %p, error getting cap\n", inode);
+                } else if (!(got & want)) {
+                        dout("start_read %p, no cache cap\n", inode);
+                        ret = 0;
+                }
+                if (ret <= 0) {
+                        if (got)
+                                ceph_put_cap_refs(ci, got);
+                        while (!list_empty(page_list)) {
+                                page = list_entry(page_list->prev,
+                                                  struct page, lru);
+                                list_del(&page->lru);
+                                put_page(page);
+                        }
+                        return ret;
+                }
+        }
 
         off = (u64) page_offset(page);
 
@@ -338,15 +363,18 @@ static int start_read(struct inode *inode, struct list_head *page_list, int max)
                                     CEPH_OSD_FLAG_READ, NULL,
                                     ci->i_truncate_seq, ci->i_truncate_size,
                                     false);
-        if (IS_ERR(req))
-                return PTR_ERR(req);
+        if (IS_ERR(req)) {
+                ret = PTR_ERR(req);
+                goto out;
+        }
 
         /* build page vector */
         nr_pages = calc_pages_for(0, len);
         pages = kmalloc(sizeof(*pages) * nr_pages, GFP_KERNEL);
-        ret = -ENOMEM;
-        if (!pages)
-                goto out;
+        if (!pages) {
+                ret = -ENOMEM;
+                goto out_put;
+        }
         for (i = 0; i < nr_pages; ++i) {
                 page = list_entry(page_list->prev, struct page, lru);
                 BUG_ON(PageLocked(page));
@@ -378,6 +406,12 @@ static int start_read(struct inode *inode, struct list_head *page_list, int max)
         if (ret < 0)
                 goto out_pages;
         ceph_osdc_put_request(req);
+
+        /* After adding locked pages to page cache, the inode holds cache cap.
+         * So we can drop our cap refs. */
+        if (got)
+                ceph_put_cap_refs(ci, got);
+
         return nr_pages;
 
 out_pages:
@@ -386,8 +420,11 @@ out_pages:
                 unlock_page(pages[i]);
         }
         ceph_put_page_vector(pages, nr_pages, false);
-out:
+out_put:
         ceph_osdc_put_request(req);
+out:
+        if (got)
+                ceph_put_cap_refs(ci, got);
         return ret;
 }
 
@@ -424,7 +461,6 @@ static int ceph_readpages(struct file *file, struct address_space *mapping,
                 rc = start_read(inode, page_list, max);
                 if (rc < 0)
                         goto out;
-                BUG_ON(rc == 0);
         }
 out:
         ceph_fscache_readpages_cancel(inode, page_list);
@@ -1371,9 +1407,11 @@ static int ceph_filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
              inode, off, (size_t)PAGE_SIZE, ceph_cap_string(got));
 
         if ((got & (CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO)) ||
-            ci->i_inline_version == CEPH_INLINE_NONE)
+            ci->i_inline_version == CEPH_INLINE_NONE) {
+                current->journal_info = vma->vm_file;
                 ret = filemap_fault(vma, vmf);
-        else
+                current->journal_info = NULL;
+        } else
                 ret = -EAGAIN;
 
         dout("filemap_fault %p %llu~%zd dropping cap refs on %s ret %d\n",
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 4037b389a7e9..edb407f38b40 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2479,6 +2479,27 @@ static void check_max_size(struct inode *inode, loff_t endoff)
                 ceph_check_caps(ci, CHECK_CAPS_AUTHONLY, NULL);
 }
 
+int ceph_try_get_caps(struct ceph_inode_info *ci, int need, int want, int *got)
+{
+        int ret, err = 0;
+
+        BUG_ON(need & ~CEPH_CAP_FILE_RD);
+        BUG_ON(want & ~(CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO));
+        ret = ceph_pool_perm_check(ci, need);
+        if (ret < 0)
+                return ret;
+
+        ret = try_get_cap_refs(ci, need, want, 0, true, got, &err);
+        if (ret) {
+                if (err == -EAGAIN) {
+                        ret = 0;
+                } else if (err < 0) {
+                        ret = err;
+                }
+        }
+        return ret;
+}
+
 /*
  * Wait for caps, and take cap references.  If we can't get a WR cap
  * due to a small max_size, make sure we check_max_size (and possibly
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 10cd6acad44c..ae3cec5724d6 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -1249,8 +1249,9 @@ again:
                 dout("aio_read %p %llx.%llx %llu~%u got cap refs on %s\n",
                      inode, ceph_vinop(inode), iocb->ki_pos, (unsigned)len,
                      ceph_cap_string(got));
-
+                current->journal_info = filp;
                 ret = generic_file_read_iter(iocb, to);
+                current->journal_info = NULL;
         }
         dout("aio_read %p %llx.%llx dropping cap refs on %s = %d\n",
              inode, ceph_vinop(inode), ceph_cap_string(got), (int)ret);
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 3e3fa9163059..622d5dd9f616 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -905,6 +905,8 @@ extern int ceph_encode_dentry_release(void **p, struct dentry *dn,
 
 extern int ceph_get_caps(struct ceph_inode_info *ci, int need, int want,
                          loff_t endoff, int *got, struct page **pinned_page);
+extern int ceph_try_get_caps(struct ceph_inode_info *ci,
+                             int need, int want, int *got);
 
 /* for counting open files by mode */
 extern void __ceph_get_fmode(struct ceph_inode_info *ci, int mode);