ceph: allow queueing cap/snap handling after putting cap references

Testing with the fscache overhaul has triggered some lockdep warnings
about circular lock dependencies involving page_mkwrite and the
mmap_lock. It'd be better to do the "real work" without the mmap lock
being held.

Change the skip_checking_caps parameter in __ceph_put_cap_refs to an
enum, and use that to determine whether to queue check_caps, do it
synchronously or not at all. Change ceph_page_mkwrite to do a
ceph_put_cap_refs_async().

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/addr.c

@@ -1662,7 +1662,7 @@ static vm_fault_t ceph_page_mkwrite(struct vm_fault *vmf)
 
 	dout("page_mkwrite %p %llu~%zd dropping cap refs on %s ret %x\n",
 	     inode, off, len, ceph_cap_string(got), ret);
-	ceph_put_cap_refs(ci, got);
+	ceph_put_cap_refs_async(ci, got);
 out_free:
 	ceph_restore_sigs(&oldset);
 	sb_end_pagefault(inode->i_sb);

fs/ceph/caps.c

@@ -3027,6 +3027,12 @@ static int ceph_try_drop_cap_snap(struct ceph_inode_info *ci,
 	return 0;
 }
 
+enum put_cap_refs_mode {
+	PUT_CAP_REFS_SYNC = 0,
+	PUT_CAP_REFS_NO_CHECK,
+	PUT_CAP_REFS_ASYNC,
+};
+
 /*
  * Release cap refs.
  *
@@ -3037,7 +3043,7 @@ static int ceph_try_drop_cap_snap(struct ceph_inode_info *ci,
  * cap_snap, and wake up any waiters.
  */
 static void __ceph_put_cap_refs(struct ceph_inode_info *ci, int had,
-				bool skip_checking_caps)
+				enum put_cap_refs_mode mode)
 {
 	struct inode *inode = &ci->vfs_inode;
 	int last = 0, put = 0, flushsnaps = 0, wake = 0;
@@ -3093,11 +3099,21 @@ static void __ceph_put_cap_refs(struct ceph_inode_info *ci, int had,
 	dout("put_cap_refs %p had %s%s%s\n", inode, ceph_cap_string(had),
 	     last ? " last" : "", put ? " put" : "");
 
-	if (!skip_checking_caps) {
+	switch (mode) {
+	case PUT_CAP_REFS_SYNC:
 		if (last)
 			ceph_check_caps(ci, 0, NULL);
 		else if (flushsnaps)
 			ceph_flush_snaps(ci, NULL);
+		break;
+	case PUT_CAP_REFS_ASYNC:
+		if (last)
+			ceph_queue_check_caps(inode);
+		else if (flushsnaps)
+			ceph_queue_flush_snaps(inode);
+		break;
+	default:
+		break;
 	}
 	if (wake)
 		wake_up_all(&ci->i_cap_wq);
@@ -3107,12 +3123,17 @@ static void __ceph_put_cap_refs(struct ceph_inode_info *ci, int had,
 
 void ceph_put_cap_refs(struct ceph_inode_info *ci, int had)
 {
-	__ceph_put_cap_refs(ci, had, false);
+	__ceph_put_cap_refs(ci, had, PUT_CAP_REFS_SYNC);
+}
+
+void ceph_put_cap_refs_async(struct ceph_inode_info *ci, int had)
+{
+	__ceph_put_cap_refs(ci, had, PUT_CAP_REFS_ASYNC);
 }
 
 void ceph_put_cap_refs_no_check_caps(struct ceph_inode_info *ci, int had)
 {
-	__ceph_put_cap_refs(ci, had, true);
+	__ceph_put_cap_refs(ci, had, PUT_CAP_REFS_NO_CHECK);
 }
 
 /*

fs/ceph/inode.c

@@ -1965,6 +1965,12 @@ static void ceph_inode_work(struct work_struct *work)
 	if (test_and_clear_bit(CEPH_I_WORK_VMTRUNCATE, &ci->i_work_mask))
 		__ceph_do_pending_vmtruncate(inode);
 
+	if (test_and_clear_bit(CEPH_I_WORK_CHECK_CAPS, &ci->i_work_mask))
+		ceph_check_caps(ci, 0, NULL);
+
+	if (test_and_clear_bit(CEPH_I_WORK_FLUSH_SNAPS, &ci->i_work_mask))
+		ceph_flush_snaps(ci, NULL);
+
 	iput(inode);
 }
 

fs/ceph/super.h

@@ -562,9 +562,11 @@ static inline struct inode *ceph_find_inode(struct super_block *sb,
 /*
  * Masks of ceph inode work.
  */
-#define CEPH_I_WORK_WRITEBACK		0 /* writeback */
+#define CEPH_I_WORK_WRITEBACK		0
-#define CEPH_I_WORK_INVALIDATE_PAGES	1 /* invalidate pages */
+#define CEPH_I_WORK_INVALIDATE_PAGES	1
-#define CEPH_I_WORK_VMTRUNCATE		2 /* vmtruncate */
+#define CEPH_I_WORK_VMTRUNCATE		2
+#define CEPH_I_WORK_CHECK_CAPS		3
+#define CEPH_I_WORK_FLUSH_SNAPS		4
 
 /*
  * We set the ERROR_WRITE bit when we start seeing write errors on an inode
@@ -982,6 +984,16 @@ static inline void ceph_queue_writeback(struct inode *inode)
 	ceph_queue_inode_work(inode, CEPH_I_WORK_WRITEBACK);
 }
 
+static inline void ceph_queue_check_caps(struct inode *inode)
+{
+	ceph_queue_inode_work(inode, CEPH_I_WORK_CHECK_CAPS);
+}
+
+static inline void ceph_queue_flush_snaps(struct inode *inode)
+{
+	ceph_queue_inode_work(inode, CEPH_I_WORK_FLUSH_SNAPS);
+}
+
 extern int __ceph_do_getattr(struct inode *inode, struct page *locked_page,
 			     int mask, bool force);
 static inline int ceph_do_getattr(struct inode *inode, int mask, bool force)
@@ -1120,6 +1132,7 @@ extern void ceph_take_cap_refs(struct ceph_inode_info *ci, int caps,
 				bool snap_rwsem_locked);
 extern void ceph_get_cap_refs(struct ceph_inode_info *ci, int caps);
 extern void ceph_put_cap_refs(struct ceph_inode_info *ci, int had);
+extern void ceph_put_cap_refs_async(struct ceph_inode_info *ci, int had);
 extern void ceph_put_cap_refs_no_check_caps(struct ceph_inode_info *ci,
 					    int had);
 extern void ceph_put_wrbuffer_cap_refs(struct ceph_inode_info *ci, int nr,