Hi,
On 16 Oct 2014, at 00:12, Andreas Dilger <adilger@xxxxxxxxx> wrote:
> 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.
Sure, would be nice to have it. And I will get round to it one day but no customer has ever requested it so at least I haven't implemented it yet...
Best regards,
Anton
> 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. */
--
Anton Altaparmakov <anton at tuxera.com> (replace at with @)
Senior Kernel Engineer, Tuxera Inc., http://www.tuxera.com/
Linux NTFS maintainer
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