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Commit 86056090 authored by Yan, Zheng's avatar Yan, Zheng Committed by Ilya Dryomov
Browse files

ceph: avoid sending unnessesary FLUSHSNAP message 



when a snap notification contains no new snapshot, we can avoid
sending FLUSHSNAP message to MDS. But we still need to create
cap_snap in some case because it's required by write path and
page writeback path

Signed-off-by: default avatarYan, Zheng <zyan@redhat.com>
parent 5dda377c

fs/ceph/caps.c

+38 −31
Original line number Diff line number Diff line
@@ -1297,11 +1297,8 @@ void __ceph_flush_snaps(struct ceph_inode_info *ci, 
		if (capsnap->dirty_pages || capsnap->writing)

			break;



		/*

		 * if cap writeback already occurred, we should have dropped

		 * the capsnap in ceph_put_wrbuffer_cap_refs.

		 */

		BUG_ON(capsnap->dirty == 0);

		/* should be removed by ceph_try_drop_cap_snap() */

		BUG_ON(!capsnap->need_flush);



		/* pick mds, take s_mutex */

		if (ci->i_auth_cap == NULL) {
@@ -2347,6 +2344,27 @@ void ceph_get_cap_refs(struct ceph_inode_info *ci, int caps) 
	spin_unlock(&ci->i_ceph_lock);

}





/*

 * drop cap_snap that is not associated with any snapshot.

 * we don't need to send FLUSHSNAP message for it.

 */

static int ceph_try_drop_cap_snap(struct ceph_cap_snap *capsnap)

{

	if (!capsnap->need_flush &&

	    !capsnap->writing && !capsnap->dirty_pages) {



		dout("dropping cap_snap %p follows %llu\n",

		     capsnap, capsnap->follows);

		ceph_put_snap_context(capsnap->context);

		list_del(&capsnap->ci_item);

		list_del(&capsnap->flushing_item);

		ceph_put_cap_snap(capsnap);

		return 1;

	}

	return 0;

}



/*

 * Release cap refs.

 *
@@ -2360,7 +2378,6 @@ void ceph_put_cap_refs(struct ceph_inode_info *ci, int had) 
{

	struct inode *inode = &ci->vfs_inode;

	int last = 0, put = 0, flushsnaps = 0, wake = 0;

	struct ceph_cap_snap *capsnap;



	spin_lock(&ci->i_ceph_lock);

	if (had & CEPH_CAP_PIN)
@@ -2382,18 +2399,18 @@ void ceph_put_cap_refs(struct ceph_inode_info *ci, int had) 
	if (had & CEPH_CAP_FILE_WR)

		if (--ci->i_wr_ref == 0) {

			last++;

			if (!list_empty(&ci->i_cap_snaps)) {

				capsnap = list_first_entry(&ci->i_cap_snaps,

			if (__ceph_have_pending_cap_snap(ci)) {

				struct ceph_cap_snap *capsnap =

					list_last_entry(&ci->i_cap_snaps,

							struct ceph_cap_snap,

							ci_item);

				if (capsnap->writing) {

				capsnap->writing = 0;

					flushsnaps =

						__ceph_finish_cap_snap(ci,

								       capsnap);

				if (ceph_try_drop_cap_snap(capsnap))

					put++;

				else if (__ceph_finish_cap_snap(ci, capsnap))

					flushsnaps = 1;

				wake = 1;

			}

			}

			if (ci->i_wrbuffer_ref_head == 0 &&

			    ci->i_dirty_caps == 0 &&

			    ci->i_flushing_caps == 0) {
@@ -2416,7 +2433,7 @@ void ceph_put_cap_refs(struct ceph_inode_info *ci, int had) 
		ceph_flush_snaps(ci);

	if (wake)

		wake_up_all(&ci->i_cap_wq);

	if (put)

	while (put-- > 0)

		iput(inode);

}
@@ -2467,25 +2484,15 @@ void ceph_put_wrbuffer_cap_refs(struct ceph_inode_info *ci, int nr, 
		capsnap->dirty_pages -= nr;

		if (capsnap->dirty_pages == 0) {

			complete_capsnap = 1;

			if (capsnap->dirty == 0)

				/* cap writeback completed before we created

				 * the cap_snap; no FLUSHSNAP is needed */

				drop_capsnap = 1;

			drop_capsnap = ceph_try_drop_cap_snap(capsnap);

		}

		dout("put_wrbuffer_cap_refs on %p cap_snap %p "

		     " snap %lld %d/%d -> %d/%d %s%s%s\n",

		     " snap %lld %d/%d -> %d/%d %s%s\n",

		     inode, capsnap, capsnap->context->seq,

		     ci->i_wrbuffer_ref+nr, capsnap->dirty_pages + nr,

		     ci->i_wrbuffer_ref, capsnap->dirty_pages,

		     last ? " (wrbuffer last)" : "",

		     complete_capsnap ? " (complete capsnap)" : "",

		     drop_capsnap ? " (drop capsnap)" : "");

		if (drop_capsnap) {

			ceph_put_snap_context(capsnap->context);

			list_del(&capsnap->ci_item);

			list_del(&capsnap->flushing_item);

			ceph_put_cap_snap(capsnap);

		}

		     complete_capsnap ? " (complete capsnap)" : "");

	}



	spin_unlock(&ci->i_ceph_lock);

fs/ceph/snap.c

+37 −12
Original line number Diff line number Diff line
@@ -436,6 +436,14 @@ static int dup_array(u64 **dst, __le64 *src, u32 num) 
	return 0;

}



static bool has_new_snaps(struct ceph_snap_context *o,

			  struct ceph_snap_context *n)

{

	if (n->num_snaps == 0)

		return false;

	/* snaps are in descending order */

	return n->snaps[0] > o->seq;

}



/*

 * When a snapshot is applied, the size/mtime inode metadata is queued
@@ -455,7 +463,7 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci) 
{

	struct inode *inode = &ci->vfs_inode;

	struct ceph_cap_snap *capsnap;

	struct ceph_snap_context *old_snapc;

	struct ceph_snap_context *old_snapc, *new_snapc;

	int used, dirty;



	capsnap = kzalloc(sizeof(*capsnap), GFP_NOFS);
@@ -469,6 +477,7 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci) 
	dirty = __ceph_caps_dirty(ci);



	old_snapc = ci->i_head_snapc;

	new_snapc = ci->i_snap_realm->cached_context;



	/*

	 * If there is a write in progress, treat that as a dirty Fw,
@@ -486,20 +495,37 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci) 
		dout("queue_cap_snap %p already pending\n", inode);

		goto update_snapc;

	}

	if (ci->i_snap_realm->cached_context == ceph_empty_snapc) {

		dout("queue_cap_snap %p empty snapc\n", inode);

		goto update_snapc;

	}

	if (!(dirty & (CEPH_CAP_AUTH_EXCL|CEPH_CAP_XATTR_EXCL|

		       CEPH_CAP_FILE_EXCL|CEPH_CAP_FILE_WR))) {

	if (ci->i_wrbuffer_ref_head == 0 &&

	    !(dirty & (CEPH_CAP_ANY_EXCL|CEPH_CAP_FILE_WR))) {

		dout("queue_cap_snap %p nothing dirty|writing\n", inode);

		goto update_snapc;

	}



	BUG_ON(!old_snapc);



	dout("queue_cap_snap %p cap_snap %p queuing under %p %s\n",

	     inode, capsnap, old_snapc, ceph_cap_string(dirty));

	/*

	 * There is no need to send FLUSHSNAP message to MDS if there is

	 * no new snapshot. But when there is dirty pages or on-going

	 * writes, we still need to create cap_snap. cap_snap is needed

	 * by the write path and page writeback path.

	 *

	 * also see ceph_try_drop_cap_snap()

	 */

	if (has_new_snaps(old_snapc, new_snapc)) {

		if (dirty & (CEPH_CAP_ANY_EXCL|CEPH_CAP_FILE_WR))

			capsnap->need_flush = true;

	} else {

		if (!(used & CEPH_CAP_FILE_WR) &&

		    ci->i_wrbuffer_ref_head == 0) {

			dout("queue_cap_snap %p "

			     "no new_snap|dirty_page|writing\n", inode);

			goto update_snapc;

		}

	}



	dout("queue_cap_snap %p cap_snap %p queuing under %p %s %s\n",

	     inode, capsnap, old_snapc, ceph_cap_string(dirty),

	     capsnap->need_flush ? "" : "no_flush");

	ihold(inode);



	atomic_set(&capsnap->nref, 1);
@@ -549,9 +575,8 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci) 


update_snapc:

	if (ci->i_head_snapc) {

		ci->i_head_snapc = ceph_get_snap_context(

				ci->i_snap_realm->cached_context);

		dout(" new snapc is %p\n", ci->i_head_snapc);

		ci->i_head_snapc = ceph_get_snap_context(new_snapc);

		dout(" new snapc is %p\n", new_snapc);

	}

	spin_unlock(&ci->i_ceph_lock);

fs/ceph/super.h

+3 −2
Original line number Diff line number Diff line
@@ -164,6 +164,7 @@ struct ceph_cap_snap { 
	int writing;   /* a sync write is still in progress */

	int dirty_pages;     /* dirty pages awaiting writeback */

	bool inline_data;

	bool need_flush;

};



static inline void ceph_put_cap_snap(struct ceph_cap_snap *capsnap)
@@ -719,7 +720,7 @@ extern void ceph_snap_exit(void); 
static inline bool __ceph_have_pending_cap_snap(struct ceph_inode_info *ci)

{

	return !list_empty(&ci->i_cap_snaps) &&

		list_entry(ci->i_cap_snaps.prev, struct ceph_cap_snap,

	       list_last_entry(&ci->i_cap_snaps, struct ceph_cap_snap,

			       ci_item)->writing;

}