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Commit 5d988308 authored by Yan, Zheng's avatar Yan, Zheng Committed by Ilya Dryomov
Browse files

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: default avatar"Yan, Zheng" <zyan@redhat.com>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent 5495c2d0

fs/ceph/addr.c

+12 −7
Original line number Diff line number Diff line
@@ -299,7 +299,8 @@ static void finish_read(struct ceph_osd_request *req) 
 * 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;

fs/ceph/file.c

+8 −2
Original line number Diff line number Diff line
@@ -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 @@ static ssize_t ceph_read_iter(struct kiocb *iocb, struct iov_iter *to) 
			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);

fs/ceph/super.h

+46 −0
Original line number Diff line number Diff line
@@ -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;