ceph: track read contexts in ceph_file_info

BugLink: https://bugs.launchpad.net/bugs/1783246
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>
(cherry picked from commit 5d988308283ecf062fa88f20ae05c52cce0bcdca)
Signed-off-by: Daniel Axtens <daniel.axtens@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index dbf07051aacd26b3daafd1e87a0e1d7e36fe553c..78a1208b878e5cbf55a718a1fe93c22738975da1 100644 (file)
--- 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 6d653235e323bac54d69d4feae78834ce648fdc3..84eafb5ce65ded1b680728f480f6e8500f45641e 100644 (file)
--- 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 */
@@ -1202,12 +1207,13 @@ 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 2beeec07fa76ce199e7d461831b9b93a705419ee..dd59bc7d2c3d14fae06372edbec8fb55f5251e0f 100644 (file)
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -668,6 +668,9 @@ 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;
@@ -684,6 +687,49 @@ 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;