On 12/02/2015 06:33 AM, John Haxby wrote: > >> On 1 Dec 2015, at 07:08, Junxiao Bi <junxiao...@oracle.com >> <mailto:junxiao...@oracle.com>> wrote: >> >> On 11/25/2015 05:07 AM, John Haxby wrote: >>> Some versions of tar assume that files with st_blocks == 0 do not >>> contain any data and will skip reading them entirely. See also >>> commit 9206c561554c ("ext4: return non-zero st_blocks for inline data"). >>> >>> Signed-off-by: John Haxby <john.ha...@oracle.com >>> <mailto:john.ha...@oracle.com>> >>> --- >>> fs/ocfs2/file.c | 8 ++++++++ >>> 1 file changed, 8 insertions(+) >>> >>> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c >>> index 0e5b451..d631279 100644 >>> --- a/fs/ocfs2/file.c >>> +++ b/fs/ocfs2/file.c >>> @@ -1302,6 +1302,14 @@ int ocfs2_getattr(struct vfsmount *mnt, >>> } >>> >>> generic_fillattr(inode, stat); >>> +/* >>> + * If there is inline data in the inode, the inode will normally not >>> + * have data blocks allocated (it may have an external xattr block). >>> + * Report at least one sector for such files, so tools like tar, rsync, >>> + * others don't incorrectly think the file is completely sparse. >>> + */ >>> +if (unlikely(OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL)) >>> +stat->blocks += (stat->size + 511)>>9; >> From filesystem side, looks reasonable that data block is 0 for >> inlined-data file. This is like a hack to filesystem to fix tools issue. >> Indeed tar-1.26-27 have been fixed to not think file with st_blocks == 0 >> empty. But I am not sure why ext4 merge that fix. > > It’s not just tar and it’s not just ext4. Programmers not unreasonably > assume that a file occupying zero blocks contains no data (where would > you put it?) > > ext4, btrfs and ntfs-3g all give inlined files a non-zero block size to > avoid surprising programmers. There’s nothing in Posix that says what > stat’s st_blocks so in this case it’s right for the file systems in > question to stick to the principle of least surprise. In this case, it > would be surprising if some small files suddenly started occupying no > space while being non-empty. It’s not as though it would be > consistent: some small files would occupy space and some would not. We > want to present a consistent view of files to the user. It’s not as > though we’re breaking du either: it already tells lies :) > > Does that make sense now? OK. Thanks you for the explanation. We'd better not surprise programmers and keep align with other fs. So
Reviewed-by: Junxiao Bi <junxiao...@oracle.com> > > jch > > >> >> Thanks, >> Junxiao. >> >>> >>> /* We set the blksize from the cluster size for performance */ >>> stat->blksize = osb->s_clustersize; > _______________________________________________ Ocfs2-devel mailing list Ocfs2-devel@oss.oracle.com https://oss.oracle.com/mailman/listinfo/ocfs2-devel
