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>

1 files changed, 8 insertions, 2 deletions

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);