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Merged
lacraig2 merged 1 commit into from
Jun 3, 2026
Merged

Use per-device dynamic devfs numbers #73

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95 changes: 14 additions & 81 deletions src/portal/portal_devfs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -86,20 +86,6 @@ static DEFINE_SPINLOCK(devfs_dir_lock);
// We need a class to trigger devtmpfs to create /dev nodes.
static struct class *portal_class = NULL;

/*
* Dynamic devices should share one devtmpfs major. Allocating a new
* dynamic major for every synthetic device makes /dev state unnecessarily
* fragmented and differs from how a single virtual driver normally behaves.
*/
#define PORTAL_DYNAMIC_DEV_MINORS 4096
static DEFINE_MUTEX(portal_dynamic_chr_lock);
static dev_t portal_dynamic_chr_devt;
static atomic_t portal_dynamic_chr_minor = ATOMIC_INIT(0);

static DEFINE_MUTEX(portal_dynamic_blk_lock);
static int portal_dynamic_blk_major;
static atomic_t portal_dynamic_blk_minor = ATOMIC_INIT(0);

/* * -------------------------------------------------------------------------
* Helpers
* -------------------------------------------------------------------------
Expand Down Expand Up @@ -449,59 +435,6 @@ static void ensure_portal_class(void)
}
}

static int alloc_portal_dynamic_chrdev(dev_t *devt)
{
int ret;
int minor;

mutex_lock(&portal_dynamic_chr_lock);
if (!portal_dynamic_chr_devt) {
ret = alloc_chrdev_region(&portal_dynamic_chr_devt, 0,
PORTAL_DYNAMIC_DEV_MINORS, "portal");
if (ret < 0) {
mutex_unlock(&portal_dynamic_chr_lock);
return ret;
}
}

minor = atomic_inc_return(&portal_dynamic_chr_minor) - 1;
if (minor >= PORTAL_DYNAMIC_DEV_MINORS) {
mutex_unlock(&portal_dynamic_chr_lock);
return -ENOSPC;
}

*devt = MKDEV(MAJOR(portal_dynamic_chr_devt), minor);
mutex_unlock(&portal_dynamic_chr_lock);
return 0;
}

static int alloc_portal_dynamic_blkdev(int *major, int *minor)
{
int ret;
int next_minor;

mutex_lock(&portal_dynamic_blk_lock);
if (!portal_dynamic_blk_major) {
ret = register_blkdev(0, "portal");
if (ret < 0) {
mutex_unlock(&portal_dynamic_blk_lock);
return ret;
}
portal_dynamic_blk_major = ret;
}

next_minor = atomic_inc_return(&portal_dynamic_blk_minor) - 1;
if (next_minor >= PORTAL_DYNAMIC_DEV_MINORS) {
mutex_unlock(&portal_dynamic_blk_lock);
return -ENOSPC;
}

*major = portal_dynamic_blk_major;
*minor = next_minor;
mutex_unlock(&portal_dynamic_blk_lock);
return 0;
}

/* * -------------------------------------------------------------------------
* Directory Logic (New)
* -------------------------------------------------------------------------
Expand Down Expand Up @@ -629,14 +562,14 @@ void handle_op_devfs_create_device(portal_region *mem_region)
* ===================================================================== */
if (pe->is_block) {
int major = req->major;
int minor = req->minor;
bool fixed_blkdev_major = major >= 0;
int minor = req->major >= 0 ? req->minor : 0;

// 1. Register Major
if (fixed_blkdev_major) {
if (major >= 0) {
ret = register_blkdev(major, final_device_name);
} else {
ret = alloc_portal_dynamic_blkdev(&major, &minor);
ret = register_blkdev(0, final_device_name);
if (ret >= 0) major = ret;
}
if (ret < 0) goto fail_alloc;

Expand Down Expand Up @@ -664,21 +597,21 @@ void handle_op_devfs_create_device(portal_region *mem_region)
pe->gd = blk_mq_alloc_disk(&pe->tag_set, &lim, pe);
}
if (IS_ERR(pe->gd)) {
if (fixed_blkdev_major) unregister_blkdev(major, final_device_name);
unregister_blkdev(major, final_device_name);
goto fail_alloc;
}
pe->gd->minors = 1;
#elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 14, 0)
pe->gd = blk_mq_alloc_disk(&pe->tag_set, pe);
if (IS_ERR(pe->gd)) {
if (fixed_blkdev_major) unregister_blkdev(major, final_device_name);
unregister_blkdev(major, final_device_name);
goto fail_alloc;
}
pe->gd->minors = 1;
#else
pe->gd = alloc_disk(1);
if (!pe->gd) {
if (fixed_blkdev_major) unregister_blkdev(major, final_device_name);
unregister_blkdev(major, final_device_name);
goto fail_alloc;
}
pe->gd->queue = blk_mq_init_queue(&pe->tag_set);
Expand All @@ -701,7 +634,7 @@ void handle_op_devfs_create_device(portal_region *mem_region)
ret = add_disk(pe->gd);
if (ret) {
put_disk(pe->gd);
if (fixed_blkdev_major) unregister_blkdev(major, final_device_name);
unregister_blkdev(major, final_device_name);
goto fail_alloc;
}
#else
Expand All @@ -713,14 +646,14 @@ void handle_op_devfs_create_device(portal_region *mem_region)
} else {
bool enable_default_mmap = (req->size > 0 || req->support_mmap);

bool fixed_chrdev_region = req->major >= 0;
bool dynamic_chrdev_region = req->major < 0;

if (fixed_chrdev_region) {
if (dynamic_chrdev_region) {
ret = alloc_chrdev_region(&devt, 0, 1, final_device_name);
} else {
devt = MKDEV(req->major, req->minor);
if (req->replace) unregister_chrdev_region(devt, 1);
ret = register_chrdev_region(devt, 1, final_device_name);
} else {
ret = alloc_portal_dynamic_chrdev(&devt);
}

if (ret < 0) goto fail_alloc;
Expand All @@ -732,7 +665,7 @@ void handle_op_devfs_create_device(portal_region *mem_region)
pe->cdev.owner = THIS_MODULE;

if (cdev_add(&pe->cdev, devt, 1)) {
if (fixed_chrdev_region) unregister_chrdev_region(devt, 1);
unregister_chrdev_region(devt, 1);
goto fail_alloc;
}

Expand All @@ -749,7 +682,7 @@ void handle_op_devfs_create_device(portal_region *mem_region)
list_del(&pe->list);
spin_unlock(&devfs_entry_lock);
cdev_del(&pe->cdev);
if (fixed_chrdev_region) unregister_chrdev_region(devt, 1);
unregister_chrdev_region(devt, 1);
goto fail_alloc;
}
}
Expand Down
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