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authorDavid Howells <dhowells@redhat.com>2018-06-15 17:24:50 +0300
committerDavid Howells <dhowells@redhat.com>2018-06-15 17:27:09 +0300
commit47ea0f2ebffd400d36ab5946ec8d6d6e08a67d53 (patch)
treec3100b32ecadbc87bcefad4e00079ac52f5c69b4 /fs/afs/callback.c
parent0da0b7fd73e4f20e1a987dfade0b36bb4813cf10 (diff)
downloadlinux-47ea0f2ebffd400d36ab5946ec8d6d6e08a67d53.tar.xz
afs: Optimise callback breaking by not repeating volume lookup
At the moment, afs_break_callbacks calls afs_break_one_callback() for each separate FID it was given, and the latter looks up the volume individually for each one. However, this is inefficient if two or more FIDs have the same vid as we could reuse the volume. This is complicated by cell aliasing whereby we may have multiple cells sharing a volume and can therefore have multiple callback interests for any particular volume ID. At the moment afs_break_one_callback() scans the entire list of volumes we're getting from a server and breaks the appropriate callback in every matching volume, regardless of cell. This scan is done for every FID. Optimise callback breaking by the following means: (1) Sort the FID list by vid so that all FIDs belonging to the same volume are clumped together. This is done through the use of an indirection table as we cannot do an insertion sort on the afs_callback_break array as we decode FIDs into it as we subsequently also have to decode callback info into it that corresponds by array index only. We also don't really want to bubblesort afterwards if we can avoid it. (2) Sort the server->cb_interests array by vid so that all the matching volumes are grouped together. This permits the scan to stop after finding a record that has a higher vid. (3) When breaking FIDs, we try to keep server->cb_break_lock as long as possible, caching the start point in the array for that volume group as long as possible. It might make sense to add another layer in that list and have a refcounted volume ID anchor that has the matching interests attached to it rather than being in the list. This would allow the lock to be dropped without losing the cursor. Signed-off-by: David Howells <dhowells@redhat.com>
Diffstat (limited to 'fs/afs/callback.c')
-rw-r--r--fs/afs/callback.c110
1 files changed, 93 insertions, 17 deletions
diff --git a/fs/afs/callback.c b/fs/afs/callback.c
index 571437dcb252..5f261fbf2182 100644
--- a/fs/afs/callback.c
+++ b/fs/afs/callback.c
@@ -21,6 +21,66 @@
#include "internal.h"
/*
+ * Create volume and callback interests on a server.
+ */
+static struct afs_cb_interest *afs_create_interest(struct afs_server *server,
+ struct afs_vnode *vnode)
+{
+ struct afs_vol_interest *new_vi, *vi;
+ struct afs_cb_interest *new;
+ struct hlist_node **pp;
+
+ new_vi = kzalloc(sizeof(struct afs_vol_interest), GFP_KERNEL);
+ if (!new_vi)
+ return NULL;
+
+ new = kzalloc(sizeof(struct afs_cb_interest), GFP_KERNEL);
+ if (!new) {
+ kfree(new_vi);
+ return NULL;
+ }
+
+ new_vi->usage = 1;
+ new_vi->vid = vnode->volume->vid;
+ INIT_HLIST_NODE(&new_vi->srv_link);
+ INIT_HLIST_HEAD(&new_vi->cb_interests);
+
+ refcount_set(&new->usage, 1);
+ new->sb = vnode->vfs_inode.i_sb;
+ new->vid = vnode->volume->vid;
+ new->server = afs_get_server(server);
+ INIT_HLIST_NODE(&new->cb_vlink);
+
+ write_lock(&server->cb_break_lock);
+
+ for (pp = &server->cb_volumes.first; *pp; pp = &(*pp)->next) {
+ vi = hlist_entry(*pp, struct afs_vol_interest, srv_link);
+ if (vi->vid < new_vi->vid)
+ continue;
+ if (vi->vid > new_vi->vid)
+ break;
+ vi->usage++;
+ goto found_vi;
+ }
+
+ new_vi->srv_link.pprev = pp;
+ new_vi->srv_link.next = *pp;
+ if (*pp)
+ (*pp)->pprev = &new_vi->srv_link.next;
+ *pp = &new_vi->srv_link;
+ vi = new_vi;
+ new_vi = NULL;
+found_vi:
+
+ new->vol_interest = vi;
+ hlist_add_head(&new->cb_vlink, &vi->cb_interests);
+
+ write_unlock(&server->cb_break_lock);
+ kfree(new_vi);
+ return new;
+}
+
+/*
* Set up an interest-in-callbacks record for a volume on a server and
* register it with the server.
* - Called with vnode->io_lock held.
@@ -77,20 +137,10 @@ again:
}
if (!cbi) {
- new = kzalloc(sizeof(struct afs_cb_interest), GFP_KERNEL);
+ new = afs_create_interest(server, vnode);
if (!new)
return -ENOMEM;
- refcount_set(&new->usage, 1);
- new->sb = vnode->vfs_inode.i_sb;
- new->vid = vnode->volume->vid;
- new->server = afs_get_server(server);
- INIT_LIST_HEAD(&new->cb_link);
-
- write_lock(&server->cb_break_lock);
- list_add_tail(&new->cb_link, &server->cb_interests);
- write_unlock(&server->cb_break_lock);
-
write_lock(&slist->lock);
if (!entry->cb_interest) {
entry->cb_interest = afs_get_cb_interest(new);
@@ -126,11 +176,22 @@ again:
*/
void afs_put_cb_interest(struct afs_net *net, struct afs_cb_interest *cbi)
{
+ struct afs_vol_interest *vi;
+
if (cbi && refcount_dec_and_test(&cbi->usage)) {
- if (!list_empty(&cbi->cb_link)) {
+ if (!hlist_unhashed(&cbi->cb_vlink)) {
write_lock(&cbi->server->cb_break_lock);
- list_del_init(&cbi->cb_link);
+
+ hlist_del_init(&cbi->cb_vlink);
+ vi = cbi->vol_interest;
+ cbi->vol_interest = NULL;
+ if (--vi->usage == 0)
+ hlist_del(&vi->srv_link);
+ else
+ vi = NULL;
+
write_unlock(&cbi->server->cb_break_lock);
+ kfree(vi);
afs_put_server(net, cbi->server);
}
kfree(cbi);
@@ -182,20 +243,34 @@ void afs_break_callback(struct afs_vnode *vnode)
static void afs_break_one_callback(struct afs_server *server,
struct afs_fid *fid)
{
+ struct afs_vol_interest *vi;
struct afs_cb_interest *cbi;
struct afs_iget_data data;
struct afs_vnode *vnode;
struct inode *inode;
read_lock(&server->cb_break_lock);
+ hlist_for_each_entry(vi, &server->cb_volumes, srv_link) {
+ if (vi->vid < fid->vid)
+ continue;
+ if (vi->vid > fid->vid) {
+ vi = NULL;
+ break;
+ }
+ //atomic_inc(&vi->usage);
+ break;
+ }
+
+ /* TODO: Find all matching volumes if we couldn't match the server and
+ * break them anyway.
+ */
+ if (!vi)
+ goto out;
/* Step through all interested superblocks. There may be more than one
* because of cell aliasing.
*/
- list_for_each_entry(cbi, &server->cb_interests, cb_link) {
- if (cbi->vid != fid->vid)
- continue;
-
+ hlist_for_each_entry(cbi, &vi->cb_interests, cb_vlink) {
if (fid->vnode == 0 && fid->unique == 0) {
/* The callback break applies to an entire volume. */
struct afs_super_info *as = AFS_FS_S(cbi->sb);
@@ -217,6 +292,7 @@ static void afs_break_one_callback(struct afs_server *server,
}
}
+out:
read_unlock(&server->cb_break_lock);
}