On Thu 23-09-21 10:37:51, Ming Lei wrote:
> When running ->fallocate(), blkdev_fallocate() should hold
> mapping->invalidate_lock to prevent page cache from being accessed,
> otherwise stale data may be read in page cache.
>
> Without this patch, blktests block/009 fails sometimes. With this patch,
> block/009 can pass always.
>
> Also as Jan pointed out, no pages can be created in the discarded area
> while you are holding the invalidate_lock, so remove the 2nd
> truncate_bdev_range().
>
> Cc: Jan Kara <jack@xxxxxxx>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> V2:
> - include <linux/fs.h> for avoiding implicit declaration of function
> filemap_invalidate_lock
> - remove 2nd truncate_bdev_range() as suggested by Jan
>
> block/fops.c | 21 ++++++++++-----------
> 1 file changed, 10 insertions(+), 11 deletions(-)
>
> diff --git a/block/fops.c b/block/fops.c
> index ffce6f6c68dd..1e970c247e0e 100644
> --- a/block/fops.c
> +++ b/block/fops.c
> @@ -14,6 +14,7 @@
> #include <linux/task_io_accounting_ops.h>
> #include <linux/falloc.h>
> #include <linux/suspend.h>
> +#include <linux/fs.h>
> #include "blk.h"
>
> static struct inode *bdev_file_inode(struct file *file)
> @@ -553,7 +554,8 @@ static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
> static long blkdev_fallocate(struct file *file, int mode, loff_t start,
> loff_t len)
> {
> - struct block_device *bdev = I_BDEV(bdev_file_inode(file));
> + struct inode *inode = bdev_file_inode(file);
> + struct block_device *bdev = I_BDEV(inode);
> loff_t end = start + len - 1;
> loff_t isize;
> int error;
> @@ -580,10 +582,12 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
> if ((start | len) & (bdev_logical_block_size(bdev) - 1))
> return -EINVAL;
>
> + filemap_invalidate_lock(inode->i_mapping);
> +
> /* Invalidate the page cache, including dirty pages. */
> error = truncate_bdev_range(bdev, file->f_mode, start, end);
> if (error)
> - return error;
> + goto fail;
>
> switch (mode) {
> case FALLOC_FL_ZERO_RANGE:
> @@ -600,17 +604,12 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
> GFP_KERNEL, 0);
> break;
> default:
> - return -EOPNOTSUPP;
> + error = -EOPNOTSUPP;
> }
> - if (error)
> - return error;
>
> - /*
> - * Invalidate the page cache again; if someone wandered in and dirtied
> - * a page, we just discard it - userspace has no way of knowing whether
> - * the write happened before or after discard completing...
> - */
> - return truncate_bdev_range(bdev, file->f_mode, start, end);
> + fail:
> + filemap_invalidate_unlock(inode->i_mapping);
> + return error;
> }
>
> const struct file_operations def_blk_fops = {
> --
> 2.31.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
