On Tue, May 17, 2016 at 11:29 AM, Jon Derrick
<jonathan.derrick@xxxxxxxxx> wrote:
> This patch fixes S_DAX bd_inode i_flag locking to conform to suggested
A "fix" implies that its currently broken. I don't see how it is, not
until we add an ioctl method or other path that also tries to update
the flags outside of blkdev_get() context. So, I don't think this
patch stands on its own if you were intending it to be merged
separately.
> locking rules. It is presumed that S_DAX is the only valid inode flag
> for a block device which subscribes to direct-access, and will restore
> any previously set flags if direct-access initialization fails.
>
> This reverts to i_flags behavior prior to
> bbab37ddc20bae4709bca8745c128c4f46fe63c5
> by allowing other bd_inode flags when DAX is disabled
>
> Signed-off-by: Jon Derrick <jonathan.derrick@xxxxxxxxx>
> ---
> fs/block_dev.c | 31 ++++++++++++++++++++++++++-----
> 1 file changed, 26 insertions(+), 5 deletions(-)
>
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 20a2c02..d41e37f 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -1159,6 +1159,20 @@ void bd_set_size(struct block_device *bdev, loff_t size)
> }
> EXPORT_SYMBOL(bd_set_size);
>
> +static void bd_add_dax(struct inode *inode)
> +{
> + inode_lock(inode);
> + inode->i_flags |= S_DAX;
> + inode_unlock(inode);
> +}
> +
> +static void bd_clear_dax(struct inode *inode)
> +{
> + inode_lock(inode);
> + inode->i_flags &= ~S_DAX;
> + inode_unlock(inode);
> +}
Since this is inode generic should these helpers be prefixed "i_"
rather than "bd_"?
> +
> static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part);
>
> /*
> @@ -1172,6 +1186,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
> {
> struct gendisk *disk;
> struct module *owner;
> + struct inode *inode;
> int ret;
> int partno;
> int perm = 0;
> @@ -1198,6 +1213,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
> if (!disk)
> goto out;
> owner = disk->fops->owner;
> + inode = bdev->bd_inode;
>
> disk_block_events(disk);
> mutex_lock_nested(&bdev->bd_mutex, for_part);
> @@ -1206,9 +1222,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
> bdev->bd_queue = disk->queue;
> bdev->bd_contains = bdev;
> if (IS_ENABLED(CONFIG_BLK_DEV_DAX) && disk->fops->direct_access)
> - bdev->bd_inode->i_flags = S_DAX;
> - else
> - bdev->bd_inode->i_flags = 0;
> + bd_add_dax(inode);
>
> if (!partno) {
> ret = -ENXIO;
> @@ -1228,6 +1242,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
> bdev->bd_part = NULL;
> bdev->bd_disk = NULL;
> bdev->bd_queue = NULL;
> + bd_clear_dax(inode);
> mutex_unlock(&bdev->bd_mutex);
> disk_unblock_events(disk);
> put_disk(disk);
> @@ -1239,7 +1254,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
> if (!ret) {
> bd_set_size(bdev,(loff_t)get_capacity(disk)<<9);
> if (!blkdev_dax_capable(bdev))
> - bdev->bd_inode->i_flags &= ~S_DAX;
> + bd_clear_dax(inode);
> }
>
> /*
> @@ -1276,7 +1291,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
> }
> bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9);
> if (!blkdev_dax_capable(bdev))
> - bdev->bd_inode->i_flags &= ~S_DAX;
> + bd_clear_dax(inode);
> }
> } else {
> if (bdev->bd_contains == bdev) {
> @@ -1297,6 +1312,11 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
> put_disk(disk);
> module_put(owner);
> }
> + inode_lock(inode);
> + if (inode->i_flags & S_DAX)
> + inode->i_flags = S_DAX;
> + inode_unlock(inode);
> +
Clear all other flags if S_DAX is set? Why?
> bdev->bd_openers++;
> if (for_part)
> bdev->bd_part_count++;
> @@ -1309,6 +1329,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
> bdev->bd_disk = NULL;
> bdev->bd_part = NULL;
> bdev->bd_queue = NULL;
> + bd_clear_dax(inode);
Why?
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