Commit cd045cb4 authored by Sage Weil's avatar Sage Weil
Browse files

ceph: fix rdcache_gen usage and invalidate 



We used to use rdcache_gen to indicate whether we "might" have cached
pages.  Now we just look at the mapping to determine that.  However, some
old behavior remains from that transition.

First, rdcache_gen == 0 no longer means we have no pages.  That can happen
at any time (presumably when we carry FILE_CACHE).  We should not reset it
to zero, and we should not check that it is zero.

That means that the only purpose for rdcache_revoking is to resolve races
between new issues of FILE_CACHE and an async invalidate.  If they are
equal, we should invalidate.  On success, we decrement rdcache_revoking,
so that it is no longer equal to rdcache_gen.  Similarly, if we success
in doing a sync invalidate, set revoking = gen - 1.  (This is a small
optimization to avoid doing unnecessary invalidate work and does not
affect correctness.)

Signed-off-by: default avatarSage Weil <sage@newdream.net>
parent feb4cc9b

fs/ceph/caps.c

+2 −2
Original line number Diff line number Diff line
@@ -1430,8 +1430,8 @@ static int try_nonblocking_invalidate(struct inode *inode) 
	    invalidating_gen == ci->i_rdcache_gen) {

		/* success. */

		dout("try_nonblocking_invalidate %p success\n", inode);

		ci->i_rdcache_gen = 0;

		ci->i_rdcache_revoking = 0;

		/* save any racing async invalidate some trouble */

		ci->i_rdcache_revoking = ci->i_rdcache_gen - 1;

		return 0;

	}

	dout("try_nonblocking_invalidate %p failed\n", inode);

fs/ceph/inode.c

+7 −9
Original line number Diff line number Diff line
@@ -1394,11 +1394,8 @@ static void ceph_invalidate_work(struct work_struct *work) 
	spin_lock(&inode->i_lock);

	dout("invalidate_pages %p gen %d revoking %d\n", inode,

	     ci->i_rdcache_gen, ci->i_rdcache_revoking);

	if (ci->i_rdcache_gen == 0 ||

	    ci->i_rdcache_revoking != ci->i_rdcache_gen) {

		BUG_ON(ci->i_rdcache_revoking > ci->i_rdcache_gen);

	if (ci->i_rdcache_revoking != ci->i_rdcache_gen) {

		/* nevermind! */

		ci->i_rdcache_revoking = 0;

		spin_unlock(&inode->i_lock);

		goto out;

	}
@@ -1408,15 +1405,16 @@ static void ceph_invalidate_work(struct work_struct *work) 
	ceph_invalidate_nondirty_pages(inode->i_mapping);



	spin_lock(&inode->i_lock);

	if (orig_gen == ci->i_rdcache_gen) {

	if (orig_gen == ci->i_rdcache_gen &&

	    orig_gen == ci->i_rdcache_revoking) {

		dout("invalidate_pages %p gen %d successful\n", inode,

		     ci->i_rdcache_gen);

		ci->i_rdcache_gen = 0;

		ci->i_rdcache_revoking = 0;

		ci->i_rdcache_revoking--;

		check = 1;

	} else {

		dout("invalidate_pages %p gen %d raced, gen now %d\n",

		     inode, orig_gen, ci->i_rdcache_gen);

		dout("invalidate_pages %p gen %d raced, now %d revoking %d\n",

		     inode, orig_gen, ci->i_rdcache_gen,

		     ci->i_rdcache_revoking);

	}

	spin_unlock(&inode->i_lock);

fs/ceph/super.h

+1 −3
Original line number Diff line number Diff line
@@ -293,9 +293,7 @@ struct ceph_inode_info { 
	int i_rd_ref, i_rdcache_ref, i_wr_ref;

	int i_wrbuffer_ref, i_wrbuffer_ref_head;

	u32 i_shared_gen;       /* increment each time we get FILE_SHARED */

	u32 i_rdcache_gen;      /* we increment this each time we get

				   FILE_CACHE.  If it's non-zero, we

				   _may_ have cached pages. */

	u32 i_rdcache_gen;      /* incremented each time we get FILE_CACHE. */

	u32 i_rdcache_revoking; /* RDCACHE gen to async invalidate, if any */



	struct list_head i_unsafe_writes; /* uncommitted sync writes */

CRA Git | Maintained and supported by SUSTech CRA and CCSE