svn commit: r197850 - head/sys/fs/tmpfs

[Yoshihiro Ota]

Could someone explain what was the cause and why this fixes the issue?

When I read it, it looked like that a vm object could be in 2 locations
and one of them looked the cause of the problem.
But I couldn't figure out thereafter.

Thanks,
Hiro

On Wed, 7 Oct 2009 23:17:15 +0000 (UTC)
Xin LI <delphij at FreeBSD.org> wrote:

> Author: delphij
> Date: Wed Oct  7 23:17:15 2009
> New Revision: 197850
> URL: http://svn.freebsd.org/changeset/base/197850
> 
> Log:
>   Add a special workaround to handle UIO_NOCOPY case.  This fixes data
>   corruption observed when sendfile() is being used.
>   
>   PR:		kern/127213
>   Submitted by:	gk
>   MFC after:	2 weeks
> 
> Modified:
>   head/sys/fs/tmpfs/tmpfs_vnops.c
> 
> Modified: head/sys/fs/tmpfs/tmpfs_vnops.c
> ==============================================================================
> --- head/sys/fs/tmpfs/tmpfs_vnops.c	Wed Oct  7 23:01:31 2009	(r197849)
> +++ head/sys/fs/tmpfs/tmpfs_vnops.c	Wed Oct  7 23:17:15 2009	(r197850)
> @@ -43,6 +43,8 @@ __FBSDID("$FreeBSD$");
>  #include <sys/priv.h>
>  #include <sys/proc.h>
>  #include <sys/resourcevar.h>
> +#include <sys/sched.h>
> +#include <sys/sf_buf.h>
>  #include <sys/stat.h>
>  #include <sys/systm.h>
>  #include <sys/unistd.h>
> @@ -428,15 +430,72 @@ tmpfs_setattr(struct vop_setattr_args *v
>  }
>  
>  /* --------------------------------------------------------------------- */
> +static int
> +tmpfs_nocacheread(vm_object_t tobj, vm_pindex_t idx,
> +    vm_offset_t offset, size_t tlen, struct uio *uio)
> +{
> +	vm_page_t	m;
> +	int		error;
> +
> +	VM_OBJECT_LOCK(tobj);
> +	vm_object_pip_add(tobj, 1);
> +	m = vm_page_grab(tobj, idx, VM_ALLOC_WIRED |
> +	    VM_ALLOC_ZERO | VM_ALLOC_NORMAL | VM_ALLOC_RETRY);
> +	if (m->valid != VM_PAGE_BITS_ALL) {
> +		if (vm_pager_has_page(tobj, idx, NULL, NULL)) {
> +			error = vm_pager_get_pages(tobj, &m, 1, 0);
> +			if (error != 0) {
> +				printf("tmpfs get pages from pager error [read]\n");
> +				goto out;
> +			}
> +		} else
> +			vm_page_zero_invalid(m, TRUE);
> +	}
> +	VM_OBJECT_UNLOCK(tobj);
> +	error = uiomove_fromphys(&m, offset, tlen, uio);
> +	VM_OBJECT_LOCK(tobj);
> +out:
> +	vm_page_lock_queues();
> +	vm_page_unwire(m, TRUE);
> +	vm_page_unlock_queues();
> +	vm_page_wakeup(m);
> +	vm_object_pip_subtract(tobj, 1);
> +	VM_OBJECT_UNLOCK(tobj);
> +
> +	return (error);
> +}
> +
> +static __inline int
> +tmpfs_nocacheread_buf(vm_object_t tobj, vm_pindex_t idx,
> +    vm_offset_t offset, size_t tlen, void *buf)
> +{
> +	struct uio uio;
> +	struct iovec iov;
> +
> +	uio.uio_iovcnt = 1;
> +	uio.uio_iov = &iov;
> +	iov.iov_base = buf;
> +	iov.iov_len = tlen;
> +
> +	uio.uio_offset = 0;
> +	uio.uio_resid = tlen;
> +	uio.uio_rw = UIO_READ;
> +	uio.uio_segflg = UIO_SYSSPACE;
> +	uio.uio_td = curthread;
> +
> +	return (tmpfs_nocacheread(tobj, idx, offset, tlen, &uio));
> +}
>  
>  static int
>  tmpfs_mappedread(vm_object_t vobj, vm_object_t tobj, size_t len, struct uio *uio)
>  {
> +	struct sf_buf	*sf;
>  	vm_pindex_t	idx;
>  	vm_page_t	m;
>  	vm_offset_t	offset;
>  	off_t		addr;
>  	size_t		tlen;
> +	char		*ma;
>  	int		error;
>  
>  	addr = uio->uio_offset;
> @@ -461,33 +520,30 @@ lookupvpg:
>  		vm_page_wakeup(m);
>  		VM_OBJECT_UNLOCK(vobj);
>  		return	(error);
> +	} else if (m != NULL && uio->uio_segflg == UIO_NOCOPY) {
> +		if (vm_page_sleep_if_busy(m, FALSE, "tmfsmr"))
> +			goto lookupvpg;
> +		vm_page_busy(m);
> +		VM_OBJECT_UNLOCK(vobj);
> +		sched_pin();
> +		sf = sf_buf_alloc(m, SFB_CPUPRIVATE);
> +		ma = (char *)sf_buf_kva(sf);
> +		error = tmpfs_nocacheread_buf(tobj, idx, offset, tlen,
> +		    ma + offset);
> +		if (error == 0) {
> +			uio->uio_offset += tlen;
> +			uio->uio_resid -= tlen;
> +		}
> +		sf_buf_free(sf);
> +		sched_unpin();
> +		VM_OBJECT_LOCK(vobj);
> +		vm_page_wakeup(m);
> +		VM_OBJECT_UNLOCK(vobj);
> +		return	(error);
>  	}
>  	VM_OBJECT_UNLOCK(vobj);
>  nocache:
> -	VM_OBJECT_LOCK(tobj);
> -	vm_object_pip_add(tobj, 1);
> -	m = vm_page_grab(tobj, idx, VM_ALLOC_WIRED |
> -	    VM_ALLOC_ZERO | VM_ALLOC_NORMAL | VM_ALLOC_RETRY);
> -	if (m->valid != VM_PAGE_BITS_ALL) {
> -		if (vm_pager_has_page(tobj, idx, NULL, NULL)) {
> -			error = vm_pager_get_pages(tobj, &m, 1, 0);
> -			if (error != 0) {
> -				printf("tmpfs get pages from pager error [read]\n");
> -				goto out;
> -			}
> -		} else
> -			vm_page_zero_invalid(m, TRUE);
> -	}
> -	VM_OBJECT_UNLOCK(tobj);
> -	error = uiomove_fromphys(&m, offset, tlen, uio);
> -	VM_OBJECT_LOCK(tobj);
> -out:
> -	vm_page_lock_queues();
> -	vm_page_unwire(m, TRUE);
> -	vm_page_unlock_queues();
> -	vm_page_wakeup(m);
> -	vm_object_pip_subtract(tobj, 1);
> -	VM_OBJECT_UNLOCK(tobj);
> +	error = tmpfs_nocacheread(tobj, idx, offset, tlen, uio);
>  
>  	return	(error);
>  }
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