On 8/12/25 4:03 AM, Rajeev Mishra wrote:
> The get_size() function now uses vfs_getattr_nosec() instead of
> i_size_read() to obtain file size information. This provides more
> accurate results for network filesystems where cached metadata
> may be stale, ensuring the loop device reflects the current file
> size rather than potentially outdated cached values.
>
> Signed-off-by: Rajeev Mishra <rajeevm@xxxxxxx>
> ---
> drivers/block/loop.c | 24 ++++++++++++++++++++++--
> 1 file changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 1b6ee91f8eb9..c418c47db76e 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -137,12 +137,32 @@ static void loop_global_unlock(struct loop_device *lo, bool global)
> static int max_part;
> static int part_shift;
>
> +/**
> + * get_size - calculate the effective size of a loop device
> + * @offset: offset into the backing file
> + * @sizelimit: user-specified size limit
> + * @file: the backing file
> + *
> + * Calculate the effective size of the loop device
> + *
> + * Returns: size in 512-byte sectors, or 0 if invalid
> + */
> static loff_t get_size(loff_t offset, loff_t sizelimit, struct file *file)
> {
> + struct kstat stat;
> loff_t loopsize;
> + int ret;
> +
> + /*
> + * Get the accurate file size. This will prevent caching
> + * issue that occurs at filesystem layer.
> + */
> + ret = vfs_getattr_nosec(&file->f_path, &stat, STATX_SIZE, 0);
> + if (ret)
> + return 0;
return 0 here is odd. Why not "return ret;" to propagate the error if any ?
An error may come from the underlying FS inode->i_op->getattr().
> +
> + loopsize = stat.size;
>
> - /* Compute loopsize in bytes */
> - loopsize = i_size_read(file->f_mapping->host);
> if (offset > 0)
> loopsize -= offset;
> /* offset is beyond i_size, weird but possible */
--
Damien Le Moal
Western Digital Research
