| Message ID | 1435934443-17090-6-git-send-email-matthew.r.wilcox@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 07/03/2015 05:40 PM, Matthew Wilcox wrote: > If a block device supports the ->direct_access methods, bypass the normal > DIO path and use DAX to go straight to memcpy() instead of allocating > a DIO and a BIO. > I can't remember the details but I'm not sure it is safe for mmap to go through page-cache while DAX is bypassing page-cache. (Because of the pg_mkwrite thing, while IO), do you find this code safe? I think you need to force all DAX IO through dax.c. I did not understand why we need to give the user an option? why would he ever want a cached access to a memory device (ie two copies of the same thing). Why not DAX hard coded? > Includes support for the DIO_SKIP_DIO_COUNT flag in DAX, as is done in > do_blockdev_direct_IO(). > > Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com> > --- > fs/block_dev.c | 4 ++++ > fs/dax.c | 6 ++++-- > 2 files changed, 8 insertions(+), 2 deletions(-) > > diff --git a/fs/block_dev.c b/fs/block_dev.c > index 4fe10f9..0bb2993 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -152,6 +152,9 @@ blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, loff_t offset) > struct file *file = iocb->ki_filp; > struct inode *inode = file->f_mapping->host; > > + if (IS_DAX(inode)) > + return dax_do_io(iocb, inode, iter, offset, blkdev_get_block, > + NULL, DIO_SKIP_DIO_COUNT); > return __blockdev_direct_IO(iocb, inode, I_BDEV(inode), iter, offset, > blkdev_get_block, NULL, NULL, > DIO_SKIP_DIO_COUNT); > @@ -1170,6 +1173,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) > bdev->bd_disk = disk; > bdev->bd_queue = disk->queue; > bdev->bd_contains = bdev; > + bdev->bd_inode->i_flags = disk->fops->direct_access ? S_DAX : 0; > if (!partno) { > ret = -ENXIO; > bdev->bd_part = disk_get_part(disk, partno); > diff --git a/fs/dax.c b/fs/dax.c > index eaa9e06..c3e21cc 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -209,7 +209,8 @@ ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode, > } > > /* Protects against truncate */ > - inode_dio_begin(inode); > + if (!(flags & DIO_SKIP_DIO_COUNT)) > + inode_dio_begin(inode); Is really a separate issue, is it not? > > retval = dax_io(inode, iter, pos, end, get_block, &bh); > > @@ -219,7 +220,8 @@ ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode, > if ((retval > 0) && end_io) > end_io(iocb, pos, retval, bh.b_private); > > - inode_dio_end(inode); > + if (!(flags & DIO_SKIP_DIO_COUNT)) > + inode_dio_end(inode); > out: > return retval; > } > This scares me, the mix of DAX while cached data. I'd vote for hard-coded DAX all over. Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/block_dev.c b/fs/block_dev.c index 4fe10f9..0bb2993 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -152,6 +152,9 @@ blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, loff_t offset) struct file *file = iocb->ki_filp; struct inode *inode = file->f_mapping->host; + if (IS_DAX(inode)) + return dax_do_io(iocb, inode, iter, offset, blkdev_get_block, + NULL, DIO_SKIP_DIO_COUNT); return __blockdev_direct_IO(iocb, inode, I_BDEV(inode), iter, offset, blkdev_get_block, NULL, NULL, DIO_SKIP_DIO_COUNT); @@ -1170,6 +1173,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) bdev->bd_disk = disk; bdev->bd_queue = disk->queue; bdev->bd_contains = bdev; + bdev->bd_inode->i_flags = disk->fops->direct_access ? S_DAX : 0; if (!partno) { ret = -ENXIO; bdev->bd_part = disk_get_part(disk, partno); diff --git a/fs/dax.c b/fs/dax.c index eaa9e06..c3e21cc 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -209,7 +209,8 @@ ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode, } /* Protects against truncate */ - inode_dio_begin(inode); + if (!(flags & DIO_SKIP_DIO_COUNT)) + inode_dio_begin(inode); retval = dax_io(inode, iter, pos, end, get_block, &bh); @@ -219,7 +220,8 @@ ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode, if ((retval > 0) && end_io) end_io(iocb, pos, retval, bh.b_private); - inode_dio_end(inode); + if (!(flags & DIO_SKIP_DIO_COUNT)) + inode_dio_end(inode); out: return retval; }
If a block device supports the ->direct_access methods, bypass the normal DIO path and use DAX to go straight to memcpy() instead of allocating a DIO and a BIO. Includes support for the DIO_SKIP_DIO_COUNT flag in DAX, as is done in do_blockdev_direct_IO(). Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com> --- fs/block_dev.c | 4 ++++ fs/dax.c | 6 ++++-- 2 files changed, 8 insertions(+), 2 deletions(-)