ceph: track read contexts in ceph_file_info

Previously ceph_read_iter() uses current->journal to pass context info
to ceph_readpages(), so that ceph_readpages() can distinguish read(2)
from readahead(2)/fadvise(2)/madvise(2). The problem is that page fault
can happen when copying data to userspace memory. Page fault may call
other filesystem's page_mkwrite() if the userspace memory is mapped to a
file. The later filesystem may also want to use current->journal.

The fix is define a on-stack data structure in ceph_read_iter(), add it
to context list in ceph_file_info. ceph_readpages() searches the list,
find if there is a context belongs to current thread.

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

3 files changed, 66 insertions, 9 deletions

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index dbf07051aacd..78a1208b878e 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -299,7 +299,8 @@ unlock:
  * start an async read(ahead) operation.  return nr_pages we submitted
  * a read for on success, or negative error code.
  */
-static int start_read(struct inode *inode, struct list_head *page_list, int max)
+static int start_read(struct inode *inode, struct ceph_rw_context *rw_ctx,
+                      struct list_head *page_list, int max)
 {
         struct ceph_osd_client *osdc =
                 &ceph_inode_to_client(inode)->client->osdc;
@@ -316,7 +317,7 @@ static int start_read(struct inode *inode, struct list_head *page_list, int max)
         int got = 0;
         int ret = 0;
 
-        if (!current->journal_info) {
+        if (!rw_ctx) {
                 /* caller of readpages does not hold buffer and read caps
                  * (fadvise, madvise and readahead cases) */
                 int want = CEPH_CAP_FILE_CACHE;
@@ -437,6 +438,8 @@ static int ceph_readpages(struct file *file, struct address_space *mapping,
 {
         struct inode *inode = file_inode(file);
         struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
+        struct ceph_file_info *ci = file->private_data;
+        struct ceph_rw_context *rw_ctx;
         int rc = 0;
         int max = 0;
 
@@ -449,11 +452,12 @@ static int ceph_readpages(struct file *file, struct address_space *mapping,
         if (rc == 0)
                 goto out;
 
+        rw_ctx = ceph_find_rw_context(ci);
         max = fsc->mount_options->rsize >> PAGE_SHIFT;
-        dout("readpages %p file %p nr_pages %d max %d\n",
-             inode, file, nr_pages, max);
+        dout("readpages %p file %p ctx %p nr_pages %d max %d\n",
+             inode, file, rw_ctx, nr_pages, max);
         while (!list_empty(page_list)) {
-                rc = start_read(inode, page_list, max);
+                rc = start_read(inode, rw_ctx, page_list, max);
                 if (rc < 0)
                         goto out;
         }
@@ -1450,9 +1454,10 @@ static int ceph_filemap_fault(struct vm_fault *vmf)
 
         if ((got & (CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO)) ||
             ci->i_inline_version == CEPH_INLINE_NONE) {
-                current->journal_info = vma->vm_file;
+                CEPH_DEFINE_RW_CONTEXT(rw_ctx, got);
+                ceph_add_rw_context(fi, &rw_ctx);
                 ret = filemap_fault(vmf);
-                current->journal_info = NULL;
+                ceph_del_rw_context(fi, &rw_ctx);
         } else
                 ret = -EAGAIN;
 
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 770dd3b413e4..6639926eed4e 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -181,6 +181,10 @@ static int ceph_init_file(struct inode *inode, struct file *file, int fmode)
                         return -ENOMEM;
                 }
                 cf->fmode = fmode;
+
+                spin_lock_init(&cf->rw_contexts_lock);
+                INIT_LIST_HEAD(&cf->rw_contexts);
+
                 cf->next_offset = 2;
                 cf->readdir_cache_idx = -1;
                 file->private_data = cf;
@@ -464,6 +468,7 @@ int ceph_release(struct inode *inode, struct file *file)
                 ceph_mdsc_put_request(cf->last_readdir);
         kfree(cf->last_name);
         kfree(cf->dir_info);
+        WARN_ON(!list_empty(&cf->rw_contexts));
         kmem_cache_free(ceph_file_cachep, cf);
 
         /* wake up anyone waiting for caps on this inode */
@@ -1199,12 +1204,13 @@ again:
                         retry_op = READ_INLINE;
                 }
         } else {
+                CEPH_DEFINE_RW_CONTEXT(rw_ctx, got);
                 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;
+                ceph_add_rw_context(fi, &rw_ctx);
                 ret = generic_file_read_iter(iocb, to);
-                current->journal_info = NULL;
+                ceph_del_rw_context(fi, &rw_ctx);
         }
         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 75701c199b2b..601100da738f 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -669,6 +669,9 @@ struct ceph_file_info {
         short fmode;     /* initialized on open */
         short flags;     /* CEPH_F_* */
 
+        spinlock_t rw_contexts_lock;
+        struct list_head rw_contexts;
+
         /* readdir: position within the dir */
         u32 frag;
         struct ceph_mds_request *last_readdir;
@@ -685,6 +688,49 @@ struct ceph_file_info {
         int dir_info_len;
 };
 
+struct ceph_rw_context {
+        struct list_head list;
+        struct task_struct *thread;
+        int caps;
+};
+
+#define CEPH_DEFINE_RW_CONTEXT(_name, _caps)    \
+        struct ceph_rw_context _name = {        \
+                .thread = current,              \
+                .caps = _caps,                  \
+        }
+
+static inline void ceph_add_rw_context(struct ceph_file_info *cf,
+                                       struct ceph_rw_context *ctx)
+{
+        spin_lock(&cf->rw_contexts_lock);
+        list_add(&ctx->list, &cf->rw_contexts);
+        spin_unlock(&cf->rw_contexts_lock);
+}
+
+static inline void ceph_del_rw_context(struct ceph_file_info *cf,
+                                       struct ceph_rw_context *ctx)
+{
+        spin_lock(&cf->rw_contexts_lock);
+        list_del(&ctx->list);
+        spin_unlock(&cf->rw_contexts_lock);
+}
+
+static inline struct ceph_rw_context*
+ceph_find_rw_context(struct ceph_file_info *cf)
+{
+        struct ceph_rw_context *ctx, *found = NULL;
+        spin_lock(&cf->rw_contexts_lock);
+        list_for_each_entry(ctx, &cf->rw_contexts, list) {
+                if (ctx->thread == current) {
+                        found = ctx;
+                        break;
+                }
+        }
+        spin_unlock(&cf->rw_contexts_lock);
+        return found;
+}
+
 struct ceph_readdir_cache_control {
         struct page  *page;
         struct dentry **dentries;