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

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The commit 5aec776ef8 ("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
Change-Id: Ifb089bf80d8a3a44ece9f05fc0b99ee76cb11645
Signed-off-by: Pavankumar Kondeti <quic_pkondeti@quicinc.com>
This commit is contained in:
Pavankumar Kondeti
2022-12-08 16:16:37 +05:30
committed by Treehugger Robot
parent eddb2f39cd
commit ce18af9b5d
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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@@ -142,15 +142,21 @@ void dma_buf_uninit_sysfs_statistics(void)
kset_unregister(dma_buf_stats_kset); 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) 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. */ struct dma_buf_create_sysfs_entry *create_entry =
_Static_assert(sizeof(struct kobject) >= sizeof(struct work_struct), container_of(work, struct dma_buf_create_sysfs_entry, work);
"kobject is smaller than work_struct"); struct dma_buf *dmabuf = create_entry->dmabuf;
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;
/* /*
* A dmabuf is ref-counted via its file member. If this handler holds the only * A dmabuf is ref-counted via its file member. If this handler holds the only
@@ -161,6 +167,7 @@ static void sysfs_add_workfn(struct work_struct *work)
* is released, and that can't happen until the end of this function. * is released, and that can't happen until the end of this function.
*/ */
if (file_count(dmabuf->file) > 1) { 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 * kobject_init_and_add expects kobject to be zero-filled, but we have populated it
* to trigger this work function. * to trigger this work function.
@@ -185,8 +192,8 @@ static void sysfs_add_workfn(struct work_struct *work)
int dma_buf_stats_setup(struct dma_buf *dmabuf) int dma_buf_stats_setup(struct dma_buf *dmabuf)
{ {
struct dma_buf_sysfs_entry *sysfs_entry; struct dma_buf_create_sysfs_entry *create_entry;
struct work_struct *work; union dma_buf_create_sysfs_work_entry *work_entry;
if (!dmabuf || !dmabuf->file) if (!dmabuf || !dmabuf->file)
return -EINVAL; return -EINVAL;
@@ -196,21 +203,18 @@ int dma_buf_stats_setup(struct dma_buf *dmabuf)
return -EINVAL; return -EINVAL;
} }
sysfs_entry = kmalloc(sizeof(struct dma_buf_sysfs_entry), GFP_KERNEL); work_entry = kmalloc(sizeof(union dma_buf_create_sysfs_work_entry), GFP_KERNEL);
if (!sysfs_entry) if (!work_entry)
return -ENOMEM; return -ENOMEM;
sysfs_entry->dmabuf = dmabuf; dmabuf->sysfs_entry = &work_entry->sysfs_entry;
dmabuf->sysfs_entry = sysfs_entry;
/* create_entry = &work_entry->create_entry;
* The use of kobj as a work_struct is an ugly hack create_entry->dmabuf = dmabuf;
* to avoid an ABI break in this frozen kernel.
*/ INIT_WORK(&create_entry->work, sysfs_add_workfn);
work = (struct work_struct *)&dmabuf->sysfs_entry->kobj;
INIT_WORK(work, sysfs_add_workfn);
get_dma_buf(dmabuf); /* This reference will be dropped in 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; return 0;
} }