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Re: [PATCHv9-rebased2 28/37] shmem: get_unmapped_area align huge page

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  Re: [PATCHv9-rebased2 28/37] shmem: get_unmapped_area align huge page "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2016-06-17 10:10 +0200
    Re: [PATCHv9-rebased2 28/37] shmem: get_unmapped_area align huge page "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-06-17 13:40 +0200

#1424793 — Re: [PATCHv9-rebased2 28/37] shmem: get_unmapped_area align huge page

> 
> +unsigned long shmem_get_unmapped_area(struct file *file,
> +				      unsigned long uaddr, unsigned long len,
> +				      unsigned long pgoff, unsigned long flags)
> +{
> +	unsigned long (*get_area)(struct file *,
> +		unsigned long, unsigned long, unsigned long, unsigned long);
> +	unsigned long addr;
> +	unsigned long offset;
> +	unsigned long inflated_len;
> +	unsigned long inflated_addr;
> +	unsigned long inflated_offset;
> +
> +	if (len > TASK_SIZE)
> +		return -ENOMEM;
> +
> +	get_area = current->mm->get_unmapped_area;
> +	addr = get_area(file, uaddr, len, pgoff, flags);
> +
> +	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
> +		return addr;
> +	if (IS_ERR_VALUE(addr))
> +		return addr;
> +	if (addr & ~PAGE_MASK)
> +		return addr;
> +	if (addr > TASK_SIZE - len)
> +		return addr;
> +
> +	if (shmem_huge == SHMEM_HUGE_DENY)
> +		return addr;
> +	if (len < HPAGE_PMD_SIZE)
> +		return addr;
> +	if (flags & MAP_FIXED)
> +		return addr;
> +	/*
> +	 * Our priority is to support MAP_SHARED mapped hugely;
> +	 * and support MAP_PRIVATE mapped hugely too, until it is COWed.
> +	 * But if caller specified an address hint, respect that as before.
> +	 */
> +	if (uaddr)
> +		return addr;
> +
> +	if (shmem_huge != SHMEM_HUGE_FORCE) {
> +		struct super_block *sb;
> +
> +		if (file) {
> +			VM_BUG_ON(file->f_op != &shmem_file_operations);
> +			sb = file_inode(file)->i_sb;
> +		} else {
> +			/*
> +			 * Called directly from mm/mmap.c, or drivers/char/mem.c
> +			 * for "/dev/zero", to create a shared anonymous object.
> +			 */
> +			if (IS_ERR(shm_mnt))
> +				return addr;
> +			sb = shm_mnt->mnt_sb;
> +		}
> +		if (SHMEM_SB(sb)->huge != SHMEM_HUGE_NEVER)
> +			return addr;

Try to ask for a larger arena if huge page is not disabled for 
the mount(s/!=/==/)?

> +	}
> +
> +	offset = (pgoff << PAGE_SHIFT) & (HPAGE_PMD_SIZE-1);
> +	if (offset && offset + len < 2 * HPAGE_PMD_SIZE)
> +		return addr;
> +	if ((addr & (HPAGE_PMD_SIZE-1)) == offset)
> +		return addr;
> +
> +	inflated_len = len + HPAGE_PMD_SIZE - PAGE_SIZE;
> +	if (inflated_len > TASK_SIZE)
> +		return addr;
> +	if (inflated_len < len)
> +		return addr;
> +
> +	inflated_addr = get_area(NULL, 0, inflated_len, 0, flags);
> +	if (IS_ERR_VALUE(inflated_addr))
> +		return addr;
> +	if (inflated_addr & ~PAGE_MASK)
> +		return addr;
> +
> +	inflated_offset = inflated_addr & (HPAGE_PMD_SIZE-1);
> +	inflated_addr += offset - inflated_offset;
> +	if (inflated_offset > offset)
> +		inflated_addr += HPAGE_PMD_SIZE;
> +
> +	if (inflated_addr > TASK_SIZE - len)
> +		return addr;
> +	return inflated_addr;
> +}
> +
> 

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#1424963

On Fri, Jun 17, 2016 at 04:06:33PM +0800, Hillf Danton wrote:
> > 
> > +unsigned long shmem_get_unmapped_area(struct file *file,
> > +				      unsigned long uaddr, unsigned long len,
> > +				      unsigned long pgoff, unsigned long flags)
> > +{
> > +	unsigned long (*get_area)(struct file *,
> > +		unsigned long, unsigned long, unsigned long, unsigned long);
> > +	unsigned long addr;
> > +	unsigned long offset;
> > +	unsigned long inflated_len;
> > +	unsigned long inflated_addr;
> > +	unsigned long inflated_offset;
> > +
> > +	if (len > TASK_SIZE)
> > +		return -ENOMEM;
> > +
> > +	get_area = current->mm->get_unmapped_area;
> > +	addr = get_area(file, uaddr, len, pgoff, flags);
> > +
> > +	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
> > +		return addr;
> > +	if (IS_ERR_VALUE(addr))
> > +		return addr;
> > +	if (addr & ~PAGE_MASK)
> > +		return addr;
> > +	if (addr > TASK_SIZE - len)
> > +		return addr;
> > +
> > +	if (shmem_huge == SHMEM_HUGE_DENY)
> > +		return addr;
> > +	if (len < HPAGE_PMD_SIZE)
> > +		return addr;
> > +	if (flags & MAP_FIXED)
> > +		return addr;
> > +	/*
> > +	 * Our priority is to support MAP_SHARED mapped hugely;
> > +	 * and support MAP_PRIVATE mapped hugely too, until it is COWed.
> > +	 * But if caller specified an address hint, respect that as before.
> > +	 */
> > +	if (uaddr)
> > +		return addr;
> > +
> > +	if (shmem_huge != SHMEM_HUGE_FORCE) {
> > +		struct super_block *sb;
> > +
> > +		if (file) {
> > +			VM_BUG_ON(file->f_op != &shmem_file_operations);
> > +			sb = file_inode(file)->i_sb;
> > +		} else {
> > +			/*
> > +			 * Called directly from mm/mmap.c, or drivers/char/mem.c
> > +			 * for "/dev/zero", to create a shared anonymous object.
> > +			 */
> > +			if (IS_ERR(shm_mnt))
> > +				return addr;
> > +			sb = shm_mnt->mnt_sb;
> > +		}
> > +		if (SHMEM_SB(sb)->huge != SHMEM_HUGE_NEVER)
> > +			return addr;
> 
> Try to ask for a larger arena if huge page is not disabled for 
> the mount(s/!=/==/)?

<facepalm>

I mostly test with SHMEM_HUGE_FORCE as it puts more stress on the system.

Fixup:

diff --git a/mm/shmem.c b/mm/shmem.c
index e2c6b6e8387a..3f4ebe84ef61 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1979,7 +1979,7 @@ unsigned long shmem_get_unmapped_area(struct file *file,
 				return addr;
 			sb = shm_mnt->mnt_sb;
 		}
-		if (SHMEM_SB(sb)->huge != SHMEM_HUGE_NEVER)
+		if (SHMEM_SB(sb)->huge == SHMEM_HUGE_NEVER)
 			return addr;
 	}
 
-- 
 Kirill A. Shutemov

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