diff --git a/drivers/dma-buf/dma-buf-sysfs-stats.c b/drivers/dma-buf/dma-buf-sysfs-stats.c index 053baadcada9..b989b9c79d20 100644 --- a/drivers/dma-buf/dma-buf-sysfs-stats.c +++ b/drivers/dma-buf/dma-buf-sysfs-stats.c @@ -11,6 +11,7 @@ #include #include #include +#include #include "dma-buf-sysfs-stats.h" @@ -168,10 +169,46 @@ void dma_buf_uninit_sysfs_statistics(void) kset_unregister(dma_buf_stats_kset); } +static void sysfs_add_workfn(struct work_struct *work) +{ + struct dma_buf_sysfs_entry *sysfs_entry = + container_of(work, struct dma_buf_sysfs_entry, sysfs_add_work); + struct dma_buf *dmabuf = sysfs_entry->dmabuf; + + /* + * A dmabuf is ref-counted via its file member. If this handler holds the only + * reference to the dmabuf, there is no need for sysfs kobject creation. This is an + * optimization and a race; when the reference count drops to 1 immediately after + * this check it is not harmful as the sysfs entry will still get cleaned up in + * dma_buf_stats_teardown, which won't get called until the final dmabuf reference + * is released, and that can't happen until the end of this function. + */ + if (file_count(dmabuf->file) > 1) { + /* + * 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. + */ + memset(&dmabuf->sysfs_entry->kobj, 0, sizeof(dmabuf->sysfs_entry->kobj)); + dmabuf->sysfs_entry->kobj.kset = dma_buf_per_buffer_stats_kset; + if (kobject_init_and_add(&dmabuf->sysfs_entry->kobj, &dma_buf_ktype, NULL, + "%lu", file_inode(dmabuf->file)->i_ino)) { + kobject_put(&dmabuf->sysfs_entry->kobj); + dmabuf->sysfs_entry = NULL; + } + } else { + /* + * Free the sysfs_entry and reset the pointer so dma_buf_stats_teardown doesn't + * attempt to operate on it. + */ + kfree(dmabuf->sysfs_entry); + dmabuf->sysfs_entry = NULL; + } + dma_buf_put(dmabuf); +} + int dma_buf_stats_setup(struct dma_buf *dmabuf) { struct dma_buf_sysfs_entry *sysfs_entry; - int ret; if (!dmabuf || !dmabuf->file) return -EINVAL; @@ -181,25 +218,16 @@ int dma_buf_stats_setup(struct dma_buf *dmabuf) return -EINVAL; } - sysfs_entry = kzalloc(sizeof(struct dma_buf_sysfs_entry), GFP_KERNEL); + sysfs_entry = kmalloc(sizeof(struct dma_buf_sysfs_entry), GFP_KERNEL); if (!sysfs_entry) return -ENOMEM; - sysfs_entry->kobj.kset = dma_buf_per_buffer_stats_kset; sysfs_entry->dmabuf = dmabuf; - dmabuf->sysfs_entry = sysfs_entry; - /* create the directory for buffer stats */ - ret = kobject_init_and_add(&sysfs_entry->kobj, &dma_buf_ktype, NULL, - "%lu", file_inode(dmabuf->file)->i_ino); - if (ret) - goto err_sysfs_dmabuf; + INIT_WORK(&dmabuf->sysfs_entry->sysfs_add_work, sysfs_add_workfn); + get_dma_buf(dmabuf); /* This reference will be dropped in sysfs_add_workfn. */ + schedule_work(&dmabuf->sysfs_entry->sysfs_add_work); return 0; - -err_sysfs_dmabuf: - kobject_put(&sysfs_entry->kobj); - dmabuf->sysfs_entry = NULL; - return ret; } diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index c539f4a86728..1b935d19b992 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -23,6 +23,7 @@ #include #include #include +#include struct device; struct dma_buf; @@ -517,7 +518,15 @@ struct dma_buf { * `DMA-BUF statistics`_ for the uapi this enables. */ struct dma_buf_sysfs_entry { - struct kobject kobj; + union { + struct kobject kobj; + + /** @sysfs_add_work: + * + * For deferred sysfs kobject creation using a workqueue. + */ + struct work_struct sysfs_add_work; + }; struct dma_buf *dmabuf; } *sysfs_entry; #endif