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Commit 6a026589 authored by Sage Weil's avatar Sage Weil
Browse files

ceph: fix sync read eof check deadlock 



If a sync read gets a short result from the OSD, it may need to do a
getattr to see if it is short due to reaching end-of-file.  The getattr
was being done while holding a reference to FILE_RD, which can lead to
a deadlock if the MDS is revoking that capability bit and can't process
the getattr until it does.

We fix this by setting a flag if EOF size validation is needed, and doing
the getattr in ceph_aio_read, after the RD cap ref is dropped.  If the
read needs to be continued, we loop and continue traversing the file.

Signed-off-by: default avatarSage Weil <sage@newdream.net>
parent 68c28323

fs/ceph/file.c

+26 −13
Original line number Diff line number Diff line
@@ -431,7 +431,8 @@ static void zero_page_vector_range(int off, int len, struct page **pages) 
 */

static int striped_read(struct inode *inode,

			u64 off, u64 len,

			struct page **pages, int num_pages)

			struct page **pages, int num_pages,

			int *checkeof)

{

	struct ceph_client *client = ceph_inode_to_client(inode);

	struct ceph_inode_info *ci = ceph_inode(inode);
@@ -497,15 +498,7 @@ static int striped_read(struct inode *inode, 
		}



		/* check i_size */

		ret = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE);

		if (ret < 0)

			goto out;



		/* hit EOF? */

		if (pos >= inode->i_size)

			goto out;



		goto more;

		*checkeof = 1;

	}



out:
@@ -522,7 +515,7 @@ static int striped_read(struct inode *inode, 
 * If the read spans object boundary, just do multiple reads.

 */

static ssize_t ceph_sync_read(struct file *file, char __user *data,

			      unsigned len, loff_t *poff)

			      unsigned len, loff_t *poff, int *checkeof)

{

	struct inode *inode = file->f_dentry->d_inode;

	struct page **pages;
@@ -552,7 +545,7 @@ static ssize_t ceph_sync_read(struct file *file, char __user *data, 
	if (ret < 0)

		goto done;



	ret = striped_read(inode, off, len, pages, num_pages);

	ret = striped_read(inode, off, len, pages, num_pages, checkeof);



	if (ret >= 0 && (file->f_flags & O_DIRECT) == 0)

		ret = copy_page_vector_to_user(pages, data, off, ret);
@@ -746,11 +739,14 @@ static ssize_t ceph_aio_read(struct kiocb *iocb, const struct iovec *iov, 
	size_t len = iov->iov_len;

	struct inode *inode = filp->f_dentry->d_inode;

	struct ceph_inode_info *ci = ceph_inode(inode);

	void *base = iov->iov_base;

	ssize_t ret;

	int got = 0;

	int checkeof = 0, read = 0;



	dout("aio_read %p %llx.%llx %llu~%u trying to get caps on %p\n",

	     inode, ceph_vinop(inode), pos, (unsigned)len, inode);

again:

	__ceph_do_pending_vmtruncate(inode);

	ret = ceph_get_caps(ci, CEPH_CAP_FILE_RD, CEPH_CAP_FILE_CACHE,

			    &got, -1);
@@ -764,7 +760,7 @@ static ssize_t ceph_aio_read(struct kiocb *iocb, const struct iovec *iov, 
	    (iocb->ki_filp->f_flags & O_DIRECT) ||

	    (inode->i_sb->s_flags & MS_SYNCHRONOUS))

		/* hmm, this isn't really async... */

		ret = ceph_sync_read(filp, iov->iov_base, len, ppos);

		ret = ceph_sync_read(filp, base, len, ppos, &checkeof);

	else

		ret = generic_file_aio_read(iocb, iov, nr_segs, pos);
@@ -772,6 +768,23 @@ static ssize_t ceph_aio_read(struct kiocb *iocb, const struct iovec *iov, 
	dout("aio_read %p %llx.%llx dropping cap refs on %s = %d\n",

	     inode, ceph_vinop(inode), ceph_cap_string(got), (int)ret);

	ceph_put_cap_refs(ci, got);



	if (checkeof && ret >= 0) {

		int statret = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE);



		/* hit EOF or hole? */

		if (statret == 0 && *ppos < inode->i_size) {

			dout("aio_read sync_read hit hole, reading more\n");

			read += ret;

			base += ret;

			len -= ret;

			checkeof = 0;

			goto again;

		}

	}

	if (ret >= 0)

		ret += read;



	return ret;

}