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IB/uverbs: Clarify and revise uverbs_close_fd 

The locking requirements here have changed slightly now that we can rely
on the ib_uverbs_file always existing and containing all the necessary
locking infrastructure.

That means we can get rid of the cleanup_mutex usage (this was protecting
the check on !uboj->context).

Otherwise, follow the same pattern that IDR uses for destroy, acquire
exclusive write access, then call destroy and the undo the 'lookup'.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Jason Gunthorpe 2018-07-10 20:55:17 -06:00
parent 5671f79b42
commit e6d5d5ddd0
1 changed files with 28 additions and 13 deletions
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41
drivers/infiniband/core/rdma_core.c
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@ -650,33 +650,48 @@ EXPORT_SYMBOL(uverbs_idr_class);
static void _uverbs_close_fd(struct ib_uobject *uobj)
{
struct ib_uverbs_file *ufile = uobj->ufile;
int ret;
mutex_lock(&ufile->cleanup_mutex);
/*
* uobject was already cleaned up, remove_commit_fd_uobject
* sets this
*/
if (!uobj->context)
return;
/* uobject was either already cleaned up or is cleaned up right now anyway */
if (!uobj->context ||
!down_read_trylock(&ufile->cleanup_rwsem))
goto unlock;
/*
* lookup_get_fd_uobject holds the kref on the struct file any time a
* FD uobj is locked, which prevents this release method from being
* invoked. Meaning we can always get the write lock here, or we have
* a kernel bug. If so dangle the pointers and bail.
*/
ret = uverbs_try_lock_object(uobj, true);
if (WARN(ret, "uverbs_close_fd() racing with lookup_get_fd_uobject()"))
return;
ret = _rdma_remove_commit_uobject(uobj, RDMA_REMOVE_CLOSE);
up_read(&ufile->cleanup_rwsem);
if (ret)
pr_warn("uverbs: unable to clean up uobject file in uverbs_close_fd.\n");
unlock:
mutex_unlock(&ufile->cleanup_mutex);
pr_warn("Unable to clean up uobject file in %s\n", __func__);
atomic_set(&uobj->usecnt, 0);
}
void uverbs_close_fd(struct file *f)
{
struct ib_uobject *uobj = f->private_data;
struct kref *uverbs_file_ref = &uobj->ufile->ref;
struct ib_uverbs_file *ufile = uobj->ufile;
if (down_read_trylock(&ufile->cleanup_rwsem)) {
_uverbs_close_fd(uobj);
up_read(&ufile->cleanup_rwsem);
}
uobj->object = NULL;
/* Matches the get in alloc_begin_fd_uobject */
kref_put(&ufile->ref, ib_uverbs_release_file);
_uverbs_close_fd(uobj);
/* Pairs with filp->private_data in alloc_begin_fd_uobject */
uverbs_uobject_put(uobj);
kref_put(uverbs_file_ref, ib_uverbs_release_file);
}
static int __uverbs_cleanup_ufile(struct ib_uverbs_file *ufile,