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IB/uverbs: Move the FD uobj type struct file allocation to alloc_commit 

Allocating the struct file during alloc_begin creates this strange
asymmetry with IDR, where the FD has two krefs pointing at it during the
pre-commit phase. In particular this makes the abort process for FD very
strange and confusing.

For instance abort currently calls the type's destroy_object twice, and
the fops release once if abort is done. This is very counter intuitive. No
fops should be called until alloc_commit succeeds, and destroy_object
should only ever be called once.

Moving the struct file allocation to the alloc_commit is now simple, as we
already support failure of rdma_alloc_commit_uobject, with all the
required rollback pieces.

This creates an understandable symmetry with IDR and simplifies/fixes the
abort handling for FD types.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Jason Gunthorpe 2018-07-10 20:55:21 -06:00
parent 2c96eb7d62
commit aba94548c9
2 changed files with 47 additions and 38 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

83
drivers/infiniband/core/rdma_core.c
View File

@ -328,11 +328,8 @@ static struct ib_uobject *alloc_begin_idr_uobject(const struct uverbs_obj_type *
static struct ib_uobject *alloc_begin_fd_uobject(const struct uverbs_obj_type *type,
struct ib_uverbs_file *ufile)
{
const struct uverbs_obj_fd_type *fd_type =
container_of(type, struct uverbs_obj_fd_type, type);
int new_fd;
struct ib_uobject *uobj;
struct file *filp;
new_fd = get_unused_fd_flags(O_CLOEXEC);
if (new_fd < 0)
@ -344,28 +341,8 @@ static struct ib_uobject *alloc_begin_fd_uobject(const struct uverbs_obj_type *t
return uobj;
}
/*
* The kref for uobj is moved into filp->private data and put in
* uverbs_close_fd(). Once anon_inode_getfile() succeeds
* uverbs_close_fd() must be guaranteed to be called from the provided
* fops release callback. We piggyback our kref of uobj on the stack
* with the lifetime of the struct file.
*/
filp = anon_inode_getfile(fd_type->name,
fd_type->fops,
uobj,
fd_type->flags);
if (IS_ERR(filp)) {
put_unused_fd(new_fd);
uverbs_uobject_put(uobj);
return (void *)filp;
}
uobj->id = new_fd;
uobj->object = filp;
uobj->ufile = ufile;
/* Matching put will be done in uverbs_close_fd() */
kref_get(&ufile->ref);
return uobj;
}
@ -407,12 +384,10 @@ static int __must_check remove_commit_idr_uobject(struct ib_uobject *uobj,
static void alloc_abort_fd_uobject(struct ib_uobject *uobj)
{
struct file *filp = uobj->object;
int id = uobj->id;
put_unused_fd(uobj->id);
/* Unsuccessful NEW */
fput(filp);
put_unused_fd(id);
/* Pairs with the kref from alloc_begin_idr_uobject */
uverbs_uobject_put(uobj);
}
static int __must_check remove_commit_fd_uobject(struct ib_uobject *uobj,
@ -500,7 +475,7 @@ int rdma_explicit_destroy(struct ib_uobject *uobject)
return ret;
}
static void alloc_commit_idr_uobject(struct ib_uobject *uobj)
static int alloc_commit_idr_uobject(struct ib_uobject *uobj)
{
struct ib_uverbs_file *ufile = uobj->ufile;
@ -514,11 +489,34 @@ static void alloc_commit_idr_uobject(struct ib_uobject *uobj)
*/
WARN_ON(idr_replace(&ufile->idr, uobj, uobj->id));
spin_unlock(&ufile->idr_lock);
return 0;
}
static void alloc_commit_fd_uobject(struct ib_uobject *uobj)
static int alloc_commit_fd_uobject(struct ib_uobject *uobj)
{
const struct uverbs_obj_fd_type *fd_type =
container_of(uobj->type, struct uverbs_obj_fd_type, type);
int fd = uobj->id;
struct file *filp;
/*
* The kref for uobj is moved into filp->private data and put in
* uverbs_close_fd(). Once alloc_commit() succeeds uverbs_close_fd()
* must be guaranteed to be called from the provided fops release
* callback.
*/
filp = anon_inode_getfile(fd_type->name,
fd_type->fops,
uobj,
fd_type->flags);
if (IS_ERR(filp))
return PTR_ERR(filp);
uobj->object = filp;
/* Matching put will be done in uverbs_close_fd() */
kref_get(&uobj->ufile->ref);
/* This shouldn't be used anymore. Use the file object instead */
uobj->id = 0;
@ -527,7 +525,9 @@ static void alloc_commit_fd_uobject(struct ib_uobject *uobj)
* NOTE: Once we install the file we loose ownership of our kref on
* uobj. It will be put by uverbs_close_fd()
*/
fd_install(fd, uobj->object);
fd_install(fd, filp);
return 0;
}
/*
@ -538,11 +538,10 @@ static void alloc_commit_fd_uobject(struct ib_uobject *uobj)
int __must_check rdma_alloc_commit_uobject(struct ib_uobject *uobj)
{
struct ib_uverbs_file *ufile = uobj->ufile;
int ret;
/* Cleanup is running. Calling this should have been impossible */
if (!down_read_trylock(&ufile->hw_destroy_rwsem)) {
int ret;
WARN(true, "ib_uverbs: Cleanup is running while allocating an uobject\n");
ret = uobj->type->type_class->remove_commit(uobj,
RDMA_REMOVE_DURING_CLEANUP);
@ -552,9 +551,18 @@ int __must_check rdma_alloc_commit_uobject(struct ib_uobject *uobj)
return ret;
}
/* matches atomic_set(-1) in alloc_uobj */
assert_uverbs_usecnt(uobj, true);
atomic_set(&uobj->usecnt, 0);
/* alloc_commit consumes the uobj kref */
ret = uobj->type->type_class->alloc_commit(uobj);
if (ret) {
if (uobj->type->type_class->remove_commit(
uobj, RDMA_REMOVE_DURING_CLEANUP))
pr_warn("ib_uverbs: cleanup of idr object %d failed\n",
uobj->id);
up_read(&ufile->hw_destroy_rwsem);
return ret;
}
/* kref is held so long as the uobj is on the uobj list. */
uverbs_uobject_get(uobj);
@ -562,8 +570,9 @@ int __must_check rdma_alloc_commit_uobject(struct ib_uobject *uobj)
list_add(&uobj->list, &ufile->uobjects);
spin_unlock_irq(&ufile->uobjects_lock);
/* alloc_commit consumes the uobj kref */
uobj->type->type_class->alloc_commit(uobj);
/* matches atomic_set(-1) in alloc_uobj */
atomic_set(&uobj->usecnt, 0);
up_read(&ufile->hw_destroy_rwsem);
return 0;

2
include/rdma/uverbs_types.h
View File

@ -73,7 +73,7 @@ struct uverbs_obj_type_class {
*/
struct ib_uobject *(*alloc_begin)(const struct uverbs_obj_type *type,
struct ib_uverbs_file *ufile);
void (*alloc_commit)(struct ib_uobject *uobj);
int (*alloc_commit)(struct ib_uobject *uobj);
void (*alloc_abort)(struct ib_uobject *uobj);
struct ib_uobject *(*lookup_get)(const struct uverbs_obj_type *type,