On Oct 15, 2014, at 1:19 PM, Sergei Antonov <saproj@xxxxxxxxx> wrote:
> Implement ntfs_bmap() function for the "bmap" address space operation.
> Now user space programs can send FIBMAP ioctl to get files' placement on
> NTFS the same way they can do it on a number of other linux filesystems.
>
> The result is returned in FIGETBSZ units, which is equal to sector size
> in ntfs driver. An error value zero is returned for resident, compressed,
> encrypted files, and for holes in sparse files.
Any thoughts about implementing FIEMAP for NTFS? This allows byte offset
granularity, and reduces the number of system calls significantly.
Cheers, Andreas
> Tested on drives with different sector sizes and different cluster sizes.
>
> Cc: Anton Altaparmakov <aia21@xxxxxxxxxx>
> Signed-off-by: Sergei Antonov <saproj@xxxxxxxxx>
> ---
> fs/ntfs/aops.c | 31 +++++++++++++++++++++++++++++++
> 1 file changed, 31 insertions(+)
>
> diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
> index d267ea6..3972b6b 100644
> --- a/fs/ntfs/aops.c
> +++ b/fs/ntfs/aops.c
> @@ -1538,6 +1538,36 @@ err_out:
>
> #endif /* NTFS_RW */
>
> +static sector_t ntfs_bmap(struct address_space *mapping, sector_t block)
> +{
> + struct inode *vi = mapping->host;
> + ntfs_inode *ni = NTFS_I(vi);
> + ntfs_volume *vol = ni->vol;
> + const unsigned clust2sect_bits = vol->cluster_size_bits -
> + vol->sector_size_bits;
> + const sector_t clust2sect_mask = (1 << clust2sect_bits) - 1;
> + LCN lcn;
> +
> + BUG_ON(S_ISDIR(vi->i_mode));
> + ntfs_debug("Requested LCN for block %llu.", (unsigned long long)block);
> + if (!NInoNonResident(ni) || NInoCompressed(ni) || NInoEncrypted(ni))
> + return 0;
> +
> + down_read(&ni->runlist.lock);
> + lcn = ntfs_attr_vcn_to_lcn_nolock(ni, block >> clust2sect_bits, false);
> + up_read(&ni->runlist.lock);
> +
> + if (lcn < 0) {
> + if (lcn == LCN_HOLE)
> + ntfs_warning(vol->sb, "Cannot get LCN for a hole.");
> + else
> + ntfs_error(vol->sb, "Error getting LCN: %lld.", lcn);
> + return 0;
> + }
> +
> + return (lcn << clust2sect_bits) + (block & clust2sect_mask);
> +}
> +
> /**
> * ntfs_aops - general address space operations for inodes and attributes
> */
> @@ -1546,6 +1576,7 @@ const struct address_space_operations ntfs_aops = {
> #ifdef NTFS_RW
> .writepage = ntfs_writepage, /* Write dirty page to disk. */
> #endif /* NTFS_RW */
> + .bmap = ntfs_bmap, /* Map file offset to volume. */
> .migratepage = buffer_migrate_page, /* Move a page cache page from
> one physical page to an
> other. */
> --
> 2.1.2
>
> --
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Cheers, Andreas
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