[PATCH v2 03/40] afs: use read_seqbegin() in afs_check_validity() and afs_getattr()

David Howells
2023-12-13T13:50:19Z

From: Oleg Nesterov <oleg@redhat.com>

David Howells says:

(3) afs_check_validity().
(4) afs_getattr().

These are both pretty short, so your solution is probably good for them.
That said, afs_vnode_commit_status() can spend a long time under the
write lock - and pretty much every file RPC op returns a status update.

Change these functions to use read_seqbegin(). This simplifies the code
and doesn't change the current behaviour, the "seq" counter is always even
so read_seqbegin_or_lock() can never take the lock.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/20231130115617.GA21584@redhat.com/
---
fs/afs/inode.c | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index 78efc9719349..a6ae74d5b698 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;
}