Re: [PATCH 01/24] GFS2: Support for FIEMAP ioctl

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 17 Dec 2008 11:30:00 +0000
swhiteho@redhat.com wrote:

> +static int gfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> +		       u64 start, u64 len)
> +{
> +	struct gfs2_inode *ip = GFS2_I(inode);
> +	struct gfs2_holder gh;
> +	int ret;
> +
> +	ret = fiemap_check_flags(fieinfo, FIEMAP_FLAG_SYNC);
> +	if (ret)
> +		return ret;
> +
> +	mutex_lock(&inode->i_mutex);
> +
> +	ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
> +	if (ret)
> +		goto out;
> +
> +	if (gfs2_is_stuffed(ip)) {
> +		u64 phys = ip->i_no_addr << inode->i_blkbits;
> +		u64 size = i_size_read(inode);

It's actually safe to directly access i_size inside i_mutex.  Although
not terribly maintainable.


> +		u32 flags = FIEMAP_EXTENT_LAST|FIEMAP_EXTENT_NOT_ALIGNED|
> +			    FIEMAP_EXTENT_DATA_INLINE;
> +		phys += sizeof(struct gfs2_dinode);
> +		phys += start;