On 3/21/07, Adam Litke <[EMAIL PROTECTED]> wrote:
The main reason I am advocating a set of pagetable_operations is to enable the development of a new hugetlb interface. During the hugetlb BOFS at OLS last year, we talked about a character device that would behave like /dev/zero. Many of the people were talking about how they just wanted to create MAP_PRIVATE hugetlb mappings without all the fuss about the hugetlbfs filesystem. /dev/zero is a familiar interface for getting anonymous memory so bringing that model to huge pages would make programming for anonymous huge pages easier.
I think we have enough infrastructure currently in hugetlbfs to implement what Adam wants for something like a /dev/hugetlb char device (except we can't afford to have a zero hugetlb page since it will be too costly on some arch). I really like the idea of having something similar to /dev/zero for hugetlb page. So I coded it up on top of existing hugetlbfs. The core change is really small and half of the patch is really just moving things around. I think this at least can partially fulfill the goal. Signed-off-by: Ken Chen <[EMAIL PROTECTED]> diff --git a/drivers/char/mem.c b/drivers/char/mem.c index f5c160c..56e58f5 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -27,6 +27,7 @@ #include <linux/bootmem.h> #include <linux/pipe_fs_i.h> #include <linux/pfn.h> +#include <linux/hugetlb.h> #include <asm/uaccess.h> #include <asm/io.h> @@ -872,6 +873,13 @@ static const struct file_operations oldmem_fops = { }; #endif +#ifdef CONFIG_HUGETLBFS +static const struct file_operations hugetlb_fops = { + .mmap = hugetlb_zero_setup, + .get_unmapped_area = hugetlb_get_unmapped_area, +}; +#endif + static ssize_t kmsg_write(struct file * file, const char __user * buf, size_t count, loff_t *ppos) { @@ -939,6 +947,11 @@ static int memory_open(struct inode * filp->f_op = &oldmem_fops; break; #endif +#ifdef CONFIG_HUGETLBFS + case 13: + filp->f_op = &hugetlb_fops; + break; +#endif default: return -ENXIO; } @@ -971,6 +984,9 @@ static const struct { #ifdef CONFIG_CRASH_DUMP {12,"oldmem", S_IRUSR | S_IWUSR | S_IRGRP, &oldmem_fops}, #endif +#ifdef CONFIG_HUGETLBFS + {13, "hugetlb",S_IRUGO | S_IWUGO, &hugetlb_fops}, +#endif }; static struct class *mem_class; diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 8c718a3..af24664 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -97,12 +97,7 @@ out: /* * Called under down_write(mmap_sem). */ - -#ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA -unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr, - unsigned long len, unsigned long pgoff, unsigned long flags); -#else -static unsigned long +unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) { @@ -150,7 +145,6 @@ full_search: addr = ALIGN(vma->vm_end, HPAGE_SIZE); } } -#endif /* * Read a page. Again trivial. If it didn't already exist @@ -734,7 +728,7 @@ static int can_do_hugetlb_shm(void) can_do_mlock()); } -struct file *hugetlb_zero_setup(size_t size) +struct file *hugetlb_file_setup(size_t size, int resv) { int error = -ENOMEM; struct file *file; @@ -771,7 +765,7 @@ struct file *hugetlb_zero_setup(size_t size) goto out_file; error = -ENOMEM; - if (hugetlb_reserve_pages(inode, 0, size >> HPAGE_SHIFT)) + if (resv && hugetlb_reserve_pages(inode, 0, size >> HPAGE_SHIFT)) goto out_inode; d_instantiate(dentry, inode); @@ -795,6 +789,18 @@ out_shm_unlock: return ERR_PTR(error); } +int hugetlb_zero_setup(struct file *file, struct vm_area_struct *vma) +{ + file = hugetlb_file_setup(vma->vm_end - vma->vm_start, 0); + if (IS_ERR(file)) + return PTR_ERR(file); + + if (vma->vm_file) + fput(vma->vm_file); + vma->vm_file = file; + return hugetlbfs_file_mmap(file, vma); +} + static int __init init_hugetlbfs_fs(void) { int error; diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 3f3e7a6..d2a2190 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -163,9 +163,12 @@ static inline struct hugetlbfs_sb_info * extern const struct file_operations hugetlbfs_file_operations; extern struct vm_operations_struct hugetlb_vm_ops; -struct file *hugetlb_zero_setup(size_t); +struct file *hugetlb_file_setup(size_t, int); +int hugetlb_zero_setup(struct file *, struct vm_area_struct *); int hugetlb_get_quota(struct address_space *mapping); void hugetlb_put_quota(struct address_space *mapping); +unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr, + unsigned long len, unsigned long pgoff, unsigned long flags); static inline int is_file_hugepages(struct file *file) { @@ -185,7 +188,7 @@ static inline void set_file_hugepages(struct file *file) #define is_file_hugepages(file) 0 #define set_file_hugepages(file) BUG() -#define hugetlb_zero_setup(size) ERR_PTR(-ENOSYS) +#define hugetlb_file_setup(size, resv) ERR_PTR(-ENOSYS) #endif /* !CONFIG_HUGETLBFS */ diff --git a/ipc/shm.c b/ipc/shm.c index 4fefbad..c64643f 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -366,7 +366,7 @@ static int newseg (struct ipc_namespace *ns if (shmflg & SHM_HUGETLB) { /* hugetlb_zero_setup takes care of mlock user accounting */ - file = hugetlb_zero_setup(size); + file = hugetlb_file_setup(size, 1); shp->mlock_user = current->user; } else { int acctflag = VM_ACCOUNT; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/