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Commit d8de9ab6 authored by Sage Weil's avatar Sage Weil
Browse files

ceph: avoid carrying Fw cap during write into page cache 



The generic_file_aio_write call may block on balance_dirty_pages while we
flush data to the OSDs.  If we hold a reference to the FILE_WR cap during
that interval revocation by the MDS (e.g., to do a stat(2)) may be very
slow.

Reviewed-by: default avatarYehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: default avatarSage Weil <sage@newdream.net>
parent 4cf9d544

fs/ceph/file.c

+19 −3
Original line number Diff line number Diff line
@@ -713,7 +713,7 @@ static ssize_t ceph_aio_write(struct kiocb *iocb, const struct iovec *iov, 
		want = CEPH_CAP_FILE_BUFFER;

	ret = ceph_get_caps(ci, CEPH_CAP_FILE_WR, want, &got, endoff);

	if (ret < 0)

		goto out;

		goto out_put;



	dout("aio_write %p %llx.%llx %llu~%u  got cap refs on %s\n",

	     inode, ceph_vinop(inode), pos, (unsigned)iov->iov_len,
@@ -726,8 +726,18 @@ static ssize_t ceph_aio_write(struct kiocb *iocb, const struct iovec *iov, 
		ret = ceph_sync_write(file, iov->iov_base, iov->iov_len,

			&iocb->ki_pos);

	} else {

		ret = generic_file_aio_write(iocb, iov, nr_segs, pos);

		/*

		 * buffered write; drop Fw early to avoid slow

		 * revocation if we get stuck on balance_dirty_pages

		 */

		int dirty;



		spin_lock(&inode->i_lock);

		dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR);

		spin_unlock(&inode->i_lock);

		ceph_put_cap_refs(ci, got);



		ret = generic_file_aio_write(iocb, iov, nr_segs, pos);

		if ((ret >= 0 || ret == -EIOCBQUEUED) &&

		    ((file->f_flags & O_SYNC) || IS_SYNC(file->f_mapping->host)

		     || ceph_osdmap_flag(osdc->osdmap, CEPH_OSDMAP_NEARFULL))) {
@@ -735,7 +745,12 @@ static ssize_t ceph_aio_write(struct kiocb *iocb, const struct iovec *iov, 
			if (err < 0)

				ret = err;

		}



		if (dirty)

			__mark_inode_dirty(inode, dirty);

		goto out;

	}



	if (ret >= 0) {

		int dirty;

		spin_lock(&inode->i_lock);
@@ -745,12 +760,13 @@ static ssize_t ceph_aio_write(struct kiocb *iocb, const struct iovec *iov, 
			__mark_inode_dirty(inode, dirty);

	}



out:

out_put:

	dout("aio_write %p %llx.%llx %llu~%u  dropping cap refs on %s\n",

	     inode, ceph_vinop(inode), pos, (unsigned)iov->iov_len,

	     ceph_cap_string(got));

	ceph_put_cap_refs(ci, got);



out:

	if (ret == -EOLDSNAPC) {

		dout("aio_write %p %llx.%llx %llu~%u got EOLDSNAPC, retrying\n",

		     inode, ceph_vinop(inode), pos, (unsigned)iov->iov_len);