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Message-ID: <20231027101205.GA31430@redhat.com>
Date: Fri, 27 Oct 2023 12:12:05 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: David Howells <dhowells@...hat.com>,
Marc Dionne <marc.dionne@...istor.com>
Cc: Chuck Lever <chuck.lever@...cle.com>,
linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] fs/afs: use read_seqbegin() rather than
read_seqbegin_or_lock()
read_seqbegin_or_lock() makes no sense unless you make "seq" odd
after the lockless access failed. See thread_group_cputime() as
an example, note that it does nextseq = 1 for the 2nd round.
So this code can use read_seqbegin() without changing the current
behaviour.
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
fs/afs/callback.c | 7 +++----
fs/afs/inode.c | 15 ++++++---------
fs/afs/server.c | 17 +++++++----------
3 files changed, 16 insertions(+), 23 deletions(-)
diff --git a/fs/afs/callback.c b/fs/afs/callback.c
index a484fa642808..b33d8a4901f8 100644
--- a/fs/afs/callback.c
+++ b/fs/afs/callback.c
@@ -110,14 +110,14 @@ static struct afs_volume *afs_lookup_volume_rcu(struct afs_cell *cell,
{
struct afs_volume *volume = NULL;
struct rb_node *p;
- int seq = 0;
+ int seq;
do {
/* Unfortunately, rbtree walking doesn't give reliable results
* under just the RCU read lock, so we have to check for
* changes.
*/
- read_seqbegin_or_lock(&cell->volume_lock, &seq);
+ seq = read_seqbegin(&cell->volume_lock);
p = rcu_dereference_raw(cell->volumes.rb_node);
while (p) {
@@ -132,9 +132,8 @@ static struct afs_volume *afs_lookup_volume_rcu(struct afs_cell *cell,
volume = NULL;
}
- } while (need_seqretry(&cell->volume_lock, seq));
+ } while (read_seqretry(&cell->volume_lock, seq));
- done_seqretry(&cell->volume_lock, seq);
return volume;
}
diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index 1c794a1896aa..88003fefff71 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -629,10 +629,10 @@ bool afs_check_validity(struct afs_vnode *vnode)
enum afs_cb_break_reason need_clear = afs_cb_break_no_break;
time64_t now = ktime_get_real_seconds();
unsigned int cb_break;
- int seq = 0;
+ int seq;
do {
- read_seqbegin_or_lock(&vnode->cb_lock, &seq);
+ seq = read_seqbegin(&vnode->cb_lock);
cb_break = vnode->cb_break;
if (test_bit(AFS_VNODE_CB_PROMISED, &vnode->flags)) {
@@ -650,9 +650,7 @@ bool afs_check_validity(struct afs_vnode *vnode)
need_clear = afs_cb_break_no_promise;
}
- } while (need_seqretry(&vnode->cb_lock, seq));
-
- done_seqretry(&vnode->cb_lock, seq);
+ } while (read_seqretry(&vnode->cb_lock, seq));
if (need_clear == afs_cb_break_no_break)
return true;
@@ -755,7 +753,7 @@ int afs_getattr(struct mnt_idmap *idmap, const struct path *path,
struct inode *inode = d_inode(path->dentry);
struct afs_vnode *vnode = AFS_FS_I(inode);
struct key *key;
- int ret, seq = 0;
+ int ret, seq;
_enter("{ ino=%lu v=%u }", inode->i_ino, inode->i_generation);
@@ -772,7 +770,7 @@ int afs_getattr(struct mnt_idmap *idmap, const struct path *path,
}
do {
- read_seqbegin_or_lock(&vnode->cb_lock, &seq);
+ seq = read_seqbegin(&vnode->cb_lock);
generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
if (test_bit(AFS_VNODE_SILLY_DELETED, &vnode->flags) &&
stat->nlink > 0)
@@ -784,9 +782,8 @@ int afs_getattr(struct mnt_idmap *idmap, const struct path *path,
*/
if (S_ISDIR(inode->i_mode))
stat->size = vnode->netfs.remote_i_size;
- } while (need_seqretry(&vnode->cb_lock, seq));
+ } while (read_seqretry(&vnode->cb_lock, seq));
- done_seqretry(&vnode->cb_lock, seq);
return 0;
}
diff --git a/fs/afs/server.c b/fs/afs/server.c
index b5237206eac3..01a26c0e0d28 100644
--- a/fs/afs/server.c
+++ b/fs/afs/server.c
@@ -27,7 +27,7 @@ struct afs_server *afs_find_server(struct afs_net *net,
const struct afs_addr_list *alist;
struct afs_server *server = NULL;
unsigned int i;
- int seq = 0, diff;
+ int seq, diff;
rcu_read_lock();
@@ -35,7 +35,8 @@ struct afs_server *afs_find_server(struct afs_net *net,
if (server)
afs_unuse_server_notime(net, server, afs_server_trace_put_find_rsq);
server = NULL;
- read_seqbegin_or_lock(&net->fs_addr_lock, &seq);
+
+ seq = read_seqbegin(&net->fs_addr_lock);
if (srx->transport.family == AF_INET6) {
const struct sockaddr_in6 *a = &srx->transport.sin6, *b;
@@ -75,9 +76,7 @@ struct afs_server *afs_find_server(struct afs_net *net,
found:
server = afs_maybe_use_server(server, afs_server_trace_get_by_addr);
- } while (need_seqretry(&net->fs_addr_lock, seq));
-
- done_seqretry(&net->fs_addr_lock, seq);
+ } while (read_seqretry(&net->fs_addr_lock, seq));
rcu_read_unlock();
return server;
@@ -90,7 +89,7 @@ struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uu
{
struct afs_server *server = NULL;
struct rb_node *p;
- int diff, seq = 0;
+ int diff, seq;
_enter("%pU", uuid);
@@ -103,7 +102,7 @@ struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uu
afs_unuse_server(net, server, afs_server_trace_put_uuid_rsq);
server = NULL;
- read_seqbegin_or_lock(&net->fs_lock, &seq);
+ seq = read_seqbegin(&net->fs_lock);
p = net->fs_servers.rb_node;
while (p) {
@@ -121,9 +120,7 @@ struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uu
server = NULL;
}
- } while (need_seqretry(&net->fs_lock, seq));
-
- done_seqretry(&net->fs_lock, seq);
+ } while (read_seqretry(&net->fs_lock, seq));
_leave(" = %p", server);
return server;
--
2.25.1.362.g51ebf55
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