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>

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 9505529..26e6643 100644 (file)
--- a/fs/ceph/addr.c
+++ b/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);

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 638d18c..abbf48f 100644 (file)
--- a/fs/ceph/caps.c
+++ b/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);
 }
 
 /*

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index e64ccd9..5d20a62 100644 (file)
--- a/fs/ceph/inode.c
+++ b/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);
 }
 

diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 59153ee..13b0288 100644 (file)
--- a/fs/ceph/super.h
+++ b/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_INVALIDATE_PAGES   1 /* invalidate pages */
-#define CEPH_I_WORK_VMTRUNCATE         2 /* vmtruncate */
+#define CEPH_I_WORK_WRITEBACK          0
+#define CEPH_I_WORK_INVALIDATE_PAGES   1
+#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,