[LU-3864] stat() on HSM released file returns st_blocks = 0

• Type: Technical task
• Resolution: Fixed
• Priority: Blocker
• Fix Version/s: Lustre 2.5.0
• Affects Version/s: Lustre 2.5.0
• Labels: HSM
• Assignee: Bruno Faccini (Inactive)
• Reporter: John Hammond

Description

HSM release in not preserving block count as reported by stat()

# cd /mnt/lustre
# dd if=/dev/zero of=Antoshka bs=1M count=10
10+0 records in
10+0 records out
10485760 bytes (10 MB) copied, 0.0740321 s, 142 MB/s
# stat Antoshka 
  File: `Antoshka'
  Size: 10485760  	Blocks: 20480      IO Block: 4194304 regular file
Device: 2c54f966h/743766374d	Inode: 144115205255725060  Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2013-08-30 10:13:48.000000000 -0500
Modify: 2013-08-30 10:13:48.000000000 -0500
Change: 2013-08-30 10:13:48.000000000 -0500
# lfs hsm_archive Antoshka 
# lfs hsm_release Antoshka
# stat Antoshka
  File: `Antoshka'
  Size: 10485760  	Blocks: 0          IO Block: 4194304 regular file
Device: 2c54f966h/743766374d	Inode: 144115205255725060  Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2013-08-30 10:13:48.000000000 -0500
Modify: 2013-08-30 10:13:48.000000000 -0500
Change: 2013-08-30 10:13:48.000000000 -0500

I had intended to fix this with LU-3811 but it will require some work in the MD* attr_set patch.

If you're thinking (philosophically) hmm, well maybe it should report a block count of 0 here then you're just wrong.

Comments

[Peter Jones]

Landed for LU-3864

[Bruno Faccini (Inactive)]

http://review.whamcloud.com/7776 has land and http://review.whamcloud.com/7584 only misses reviews now.

[Bruno Faccini (Inactive)]

Submitted patch to have st_blocks = 1 returned for released files, at http://review.whamcloud.com/7776

[Aurelien Degremont (Inactive)]

Most of filesystem does not count the space used by inode (unless there is extra block used by metadata, like for EA) when filling st_blocks, but POSIX does not say if it is only data or not.

Anyway, I think we will have to go for the "st_blocks == 1" solution.

I checked what XFS/DMF does for that. SGI says "don't use tar".... :/

[Andreas Dilger]

Note that returning st_blocks = 1 can still be justified as "correct" for HSM released files, since this is still consuming one sector on the MDT filesystem for the inode.

[Andreas Dilger]

We already do the same on the client if it only has writeback cache pages - if st_blocks == 0 but there is dirty data in the client cache we return st_blocks = 1. See cl_glimpse_lock():

                                if (cl_isize_read(inode) > 0 &&
                                    inode->i_blocks == 0) {
                                        /*
                                         * LU-417: Add dirty pages block count
                                         * lest i_blocks reports 0, some "cp" or
                                         * "tar" may think it's a completely
                                         * sparse file and skip it.
                                         */
                                        inode->i_blocks = dirty_cnt(inode);