Re: [PATCH] kill BMAPI_DEVICE

Bhagi rathi
2007-09-09T19:32:12Z

XFS_IOCORE_RT | XFS_DIFLAG_REALTIME can be set from an ioctl (xfs_setattr).
A directIO without holding ILOCK
in shared in mode can read a wrong value of di_flag for real time decision.
As a result, we may pass in-correct device
during directIO as the proposed xfs_find_bdev_for_inode doesn't hold any
lock in reading the flags. It is not based
on iocore flags as well.

On a secondary note, XFS_IOCORE_RT was set without holding iolock which
seems to an issue. I tend to leave
xfs_bmapi to decide BMAPI_DEVICE to xfs_iomap.

What is the reason why this has to be seperated?

Thanks,
-Saradhi.

On 9/9/07, Christoph Hellwig <hch@lst.de> wrote:
>
> There is no reason to go into the iomap machinery just to get the
> right block device for an inode. Instead look at the realtime flag
> in the inode and grab the right device from the mount structure.
>
> I created a new helper, xfs_find_bdev_for_inode instead of opencoding
> it because I plan to use it in other places in the future.
>
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
>
> Index: linux-2.6-xfs/fs/xfs/linux-2.6/xfs_aops.c
> ===================================================================
> --- linux-2.6-xfs.orig/fs/xfs/linux-2.6/xfs_aops.c 2007-08-23 14:54:
> 01.000000000 +0200
> +++ linux-2.6-xfs/fs/xfs/linux-2.6/xfs_aops.c 2007-08-23 14:59:
> 55.000000000 +0200
> @@ -107,6 +107,18 @@ xfs_page_trace(
> #define xfs_page_trace(tag, inode, page, pgoff)
> #endif
>
> +STATIC struct block_device *
> +xfs_find_bdev_for_inode(
> + struct xfs_inode *ip)
> +{
> + struct xfs_mount *mp = ip->i_mount;
> +
> + if (ip->i_d.di_flags & XFS_DIFLAG_REALTIME)
> + return mp->m_rtdev_targp->bt_bdev;
> + else
> + return mp->m_ddev_targp->bt_bdev;
> +}
> +
> /*
> * Schedule IO completion handling on a xfsdatad if this was
> * the final hold on this ioend. If we are asked to wait,
> @@ -1476,28 +1488,21 @@ xfs_vm_direct_IO(
> {
> struct file *file = iocb->ki_filp;
> struct inode *inode = file->f_mapping->host;
> - xfs_iomap_t iomap;
> - int maps = 1;
> - int error;
> + struct block_device *bdev;
> ssize_t ret;
>
> - error = xfs_bmap(XFS_I(inode), offset, 0,
> - BMAPI_DEVICE, &iomap, &maps);
> - if (error)
> - return -error;
> + bdev = xfs_find_bdev_for_inode(XFS_I(inode));
>
> if (rw == WRITE) {
> iocb->private = xfs_alloc_ioend(inode, IOMAP_UNWRITTEN);
> ret = blockdev_direct_IO_own_locking(rw, iocb, inode,
> - iomap.iomap_target->bt_bdev,
> - iov, offset, nr_segs,
> + bdev, iov, offset, nr_segs,
> xfs_get_blocks_direct,
> xfs_end_io_direct);
> } else {
> iocb->private = xfs_alloc_ioend(inode, IOMAP_READ);
> ret = blockdev_direct_IO_no_locking(rw, iocb, inode,
> - iomap.iomap_target->bt_bdev,
> - iov, offset, nr_segs,
> + bdev, iov, offset, nr_segs,
> xfs_get_blocks_direct,
> xfs_end_io_direct);
> }
> Index: linux-2.6-xfs/fs/xfs/xfs_iomap.c
> ===================================================================
> --- linux-2.6-xfs.orig/fs/xfs/xfs_iomap.c 2007-08-23 14:39:
> 45.000000000 +0200
> +++ linux-2.6-xfs/fs/xfs/xfs_iomap.c 2007-08-23 14:59:55.000000000+0200
> @@ -193,7 +193,7 @@ xfs_iomap(
>
> switch (flags &
> (BMAPI_READ | BMAPI_WRITE | BMAPI_ALLOCATE |
> - BMAPI_UNWRITTEN | BMAPI_DEVICE)) {
> + BMAPI_UNWRITTEN)) {
> case BMAPI_READ:
> xfs_iomap_enter_trace(XFS_IOMAP_READ_ENTER, io, offset,
> count);
> lockmode = XFS_LCK_MAP_SHARED(mp, io);
> @@ -220,13 +220,6 @@ xfs_iomap(
> break;
> case BMAPI_UNWRITTEN:
> goto phase2;
> - case BMAPI_DEVICE:
> - lockmode = XFS_LCK_MAP_SHARED(mp, io);
> - iomapp->iomap_target = io->io_flags & XFS_IOCORE_RT ?
> - mp->m_rtdev_targp : mp->m_ddev_targp;
> - error = 0;
> - *niomaps = 1;
> - goto out;
> default:
> BUG();
> }
> Index: linux-2.6-xfs/fs/xfs/xfs_iomap.h
> ===================================================================
> --- linux-2.6-xfs.orig/fs/xfs/xfs_iomap.h 2007-08-23 14:39:
> 45.000000000 +0200
> +++ linux-2.6-xfs/fs/xfs/xfs_iomap.h 2007-08-23 14:59:55.000000000+0200
> @@ -43,7 +43,6 @@ typedef enum {
> BMAPI_MMAP = (1 << 6), /* allocate for mmap write */
> BMAPI_SYNC = (1 << 7), /* sync write to flush delalloc
> space */
> BMAPI_TRYLOCK = (1 << 8), /* non-blocking request */
> - BMAPI_DEVICE = (1 << 9), /* we only want to know the device
> */
> } bmapi_flags_t;
>
>
>
>
>

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