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ANDROID: dma-buf: don't re-purpose kobject as work_struct

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The commit 5aec776ef8c9 ("BACKPORT: ANDROID: dma-buf: Move sysfs work
out of DMA-BUF export path) re-purposed kobject as work_struct temporarily
to create the sysfs entries asynchronously. The author knows what he is
doing and rightly added a build assert if kobject struct size is smaller than
the work_struct size. We are hitting this build assert on a non-GKI platform
where CONFIG_ANDROID_KABI_RESERVE is not set. Fix this problem by allocating
a new union with dma_buf_sysfs_entry structure and temporary structure as
members. We only end up allocating more memory (because of union) only when
kobject size is smaller than work_struct which the original patch any way
assumed would never be true.

Bug: 261818147
Bug: 262666413
Change-Id: Ifb089bf80d8a3a44ece9f05fc0b99ee76cb11645
Signed-off-by: Pavankumar Kondeti <quic_pkondeti@quicinc.com>
(cherry picked from commit ce18af9b5d7d0baad2ac3eea4c732d2bf128d690)
Signed-off-by: T.J. Mercier <tjmercier@google.com>
This commit is contained in:
Pavankumar Kondeti 2022-12-08 16:16:37 +05:30 committed by T.J. Mercier
parent c1b1201d39
commit 227b55a7a3
1 changed files with 24 additions and 20 deletions
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44
drivers/dma-buf/dma-buf-sysfs-stats.c
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@ -169,15 +169,21 @@ void dma_buf_uninit_sysfs_statistics(void)
kset_unregister(dma_buf_stats_kset);
}
struct dma_buf_create_sysfs_entry {
struct dma_buf *dmabuf;
struct work_struct work;
};
union dma_buf_create_sysfs_work_entry {
struct dma_buf_create_sysfs_entry create_entry;
struct dma_buf_sysfs_entry sysfs_entry;
};
static void sysfs_add_workfn(struct work_struct *work)
{
/* The ABI would have to change for this to be false, but let's be paranoid. */
_Static_assert(sizeof(struct kobject) >= sizeof(struct work_struct),
"kobject is smaller than work_struct");
struct dma_buf_sysfs_entry *sysfs_entry =
container_of((struct kobject *)work, struct dma_buf_sysfs_entry, kobj);
struct dma_buf *dmabuf = sysfs_entry->dmabuf;
struct dma_buf_create_sysfs_entry *create_entry =
container_of(work, struct dma_buf_create_sysfs_entry, work);
struct dma_buf *dmabuf = create_entry->dmabuf;
/*
* A dmabuf is ref-counted via its file member. If this handler holds the only
@ -188,6 +194,7 @@ static void sysfs_add_workfn(struct work_struct *work)
* is released, and that can't happen until the end of this function.
*/
if (file_count(dmabuf->file) > 1) {
dmabuf->sysfs_entry->dmabuf = dmabuf;
/*
* kobject_init_and_add expects kobject to be zero-filled, but we have populated it
* (the sysfs_add_work union member) to trigger this work function.
@ -212,29 +219,26 @@ static void sysfs_add_workfn(struct work_struct *work)
int dma_buf_stats_setup(struct dma_buf *dmabuf, struct file *file)
{
struct dma_buf_sysfs_entry *sysfs_entry;
struct work_struct *work;
struct dma_buf_create_sysfs_entry *create_entry;
union dma_buf_create_sysfs_work_entry *work_entry;
if (!dmabuf->exp_name) {
pr_err("exporter name must not be empty if stats needed\n");
return -EINVAL;
}
sysfs_entry = kmalloc(sizeof(struct dma_buf_sysfs_entry), GFP_KERNEL);
if (!sysfs_entry)
work_entry = kmalloc(sizeof(union dma_buf_create_sysfs_work_entry), GFP_KERNEL);
if (!work_entry)
return -ENOMEM;
sysfs_entry->dmabuf = dmabuf;
dmabuf->sysfs_entry = sysfs_entry;
dmabuf->sysfs_entry = &work_entry->sysfs_entry;
/*
* The use of kobj as a work_struct is an ugly hack
* to avoid an ABI break in this frozen kernel.
*/
work = (struct work_struct *)&dmabuf->sysfs_entry->kobj;
INIT_WORK(work, sysfs_add_workfn);
create_entry = &work_entry->create_entry;
create_entry->dmabuf = dmabuf;
INIT_WORK(&create_entry->work, sysfs_add_workfn);
get_dma_buf(dmabuf); /* This reference will be dropped in sysfs_add_workfn. */
schedule_work(work);
schedule_work(&create_entry->work);
return 0;
}