On 2020/5/13 下午1:24, Zygo Blaxell wrote: > On Wed, May 13, 2020 at 10:28:37AM +0800, Qu Wenruo wrote: >> >> >> On 2020/5/12 下午10:11, Zygo Blaxell wrote: >>> On Tue, May 12, 2020 at 09:43:06AM -0400, Zygo Blaxell wrote: >>>> On Mon, May 11, 2020 at 04:31:32PM +0800, Qu Wenruo wrote: >>>>> Hi Zygo, >>>>> >>>>> Would you like to test this diff? >>>>> >>>>> Although I haven't find a solid reason yet, there is another report and >>>>> with the help from the reporter, it turns out that balance hangs at >>>>> relocating DATA_RELOC tree block. >>>>> >>>>> After some more digging, DATA_RELOC tree doesn't need REF_COW bit at all >>>>> since we can't create snapshot for data reloc tree. >>>>> >>>>> By removing the REF_COW bit, we could ensure that data reloc tree always >>>>> get cowed for relocation (just like extent tree), this would hugely >>>>> reduce the complexity for data reloc tree. >>>>> >>>>> Not sure if this would help, but it passes my local balance run. >>>> >>>> I ran it last night. It did 30804 loops during a metadata block group >>>> balance, and is now looping on a data block group as I write this. >> >> OK, not that surprised the patch doesn't help. >> But still, the patch itself could still make sense for removing the >> REFCOW bit for data reloc tree. >> >> But I'm interesting in that, after that 30804 loops, it found its way to >> next block group?! >> >>> >>> Here's the block group that is failing, and some poking around with it: >> >> In fact, such poking would be the most valuable part. >> >>> >>> root@tester:~# ~/share/python-btrfs/examples/show_block_group_contents.py 4368594108416 /media/testfs/ >>> block group vaddr 4368594108416 length 1073741824 flags DATA used 530509824 used_pct 49 >>> extent vaddr 4368594108416 length 121053184 refs 1 gen 1318394 flags DATA >>> inline shared data backref parent 4374646833152 count 1 >>> extent vaddr 4368715161600 length 120168448 refs 1 gen 1318394 flags DATA >>> inline shared data backref parent 4374801383424 count 1 >>> extent vaddr 4368835330048 length 127623168 refs 1 gen 1318394 flags DATA >>> inline shared data backref parent 4374801383424 count 1 >>> extent vaddr 4368962953216 length 124964864 refs 1 gen 1318394 flags DATA >>> inline shared data backref parent 4374801383424 count 1 >>> extent vaddr 4369182420992 length 36700160 refs 1 gen 1321064 flags DATA >>> inline extent data backref root 257 objectid 257 offset 822607872 count 1 >> >> One interesting thing is, there are 5 extents during the loop. >> The first 4 looks like they belong to data reloc tree, which means they >> have been swapped, waiting to be cleaned up. >> >> The last one belongs to root 257, and looks like it hadn't been relocated. >> >>> >>> The extent data backref is unusual--during loops, I don't usually see those. >>> And...as I write this, it disappeared (it was part of the bees hash table, and >>> was overwritten). Now there are 4 extents reported in the balance loop (note: >>> I added a loop counter to the log message): >> >> Then it means the last one get properly relocated. > > No. In these cases the extent is removed by other filesystem activity. > If balance gets stuck looping, it can never break out of a loop if it > is the only writer on the filesystem. I've left it looping for days, > it makes no progress. > > When balance is looping, it is always stuck waiting until the extents > are removed by something else. In this particular case, the extent was > overwritten by another process removing the extent's last reference so > it was no longer part of the block group any more. It is possible to > break a balance loop by simply deleting all the files with extents in > the block group. > > I wrote some scripts that dump out the extents in the looping block > group, find the files they belong to, and run the defrag ioctl on them, > thereby removing all the extents in the block group so the balance loop > will end, without deleting the data. This should definitely be fixed. > I used the script for a while and > was able to balance hundreds of block groups more than I would have been > able to without the script; however, the script couldn't run defrag on > extents that were not reachable through open() (e.g. extents referenced > by a deleted snapshot), And data reloc tree. > so it couldn't work around the balance loops in > all cases. For the single data extent hanging you are able to reproduce, can you send me a binary dump of that fs when it's hanging? Thanks, Qu > >> The cleanup for the first 4 doesn't happen properly. >>> >>> [Tue May 12 09:44:22 2020] BTRFS info (device dm-0): found 5 extents, loops 378, stage: update data pointers >>> [Tue May 12 09:44:23 2020] BTRFS info (device dm-0): found 5 extents, loops 379, stage: update data pointers >>> [Tue May 12 09:44:24 2020] BTRFS info (device dm-0): found 5 extents, loops 380, stage: update data pointers >>> [Tue May 12 09:44:26 2020] BTRFS info (device dm-0): found 5 extents, loops 381, stage: update data pointers >>> [Tue May 12 09:44:27 2020] BTRFS info (device dm-0): found 5 extents, loops 382, stage: update data pointers >>> [Tue May 12 10:04:49 2020] BTRFS info (device dm-0): found 5 extents, loops 383, stage: update data pointers >>> [Tue May 12 10:04:53 2020] BTRFS info (device dm-0): found 4 extents, loops 384, stage: update data pointers >>> [Tue May 12 10:04:58 2020] BTRFS info (device dm-0): found 4 extents, loops 385, stage: update data pointers >>> [Tue May 12 10:05:00 2020] BTRFS info (device dm-0): found 4 extents, loops 386, stage: update data pointers >>> [Tue May 12 10:05:00 2020] BTRFS info (device dm-0): found 4 extents, loops 387, stage: update data pointers >>> [Tue May 12 10:05:01 2020] BTRFS info (device dm-0): found 4 extents, loops 388, stage: update data pointers >>> >>> Some of the extents that remain are confusing python-btrfs a little: >>> >>> root@tester:~# ~/share/python-btrfs/examples/show_block_group_data_extent_filenames.py 4368594108416 /media/testfs/ >>> block group vaddr 4368594108416 length 1073741824 flags DATA used 530509824 used_pct 49 >>> extent vaddr 4368594108416 length 121053184 refs 1 gen 1318394 flags DATA >>> Traceback (most recent call last): >>> File "/root/share/python-btrfs/examples/show_block_group_data_extent_filenames.py", line 52, in >>> inodes, bytes_missed = logical_to_ino_fn(fs.fd, extent.vaddr) >>> File "/root/share/python-btrfs/examples/show_block_group_data_extent_filenames.py", line 28, in find_out_about_v1_or_v2 >>> inodes, bytes_missed = using_v2(fd, vaddr) >>> File "/root/share/python-btrfs/examples/show_block_group_data_extent_filenames.py", line 17, in using_v2 >>> inodes, bytes_missed = btrfs.ioctl.logical_to_ino_v2(fd, vaddr, ignore_offset=True) >>> File "/media/share/python-btrfs/examples/btrfs/ioctl.py", line 565, in logical_to_ino_v2 >>> return _logical_to_ino(fd, vaddr, bufsize, ignore_offset, _v2=True) >>> File "/media/share/python-btrfs/examples/btrfs/ioctl.py", line 581, in _logical_to_ino >>> fcntl.ioctl(fd, IOC_LOGICAL_INO_V2, args) >> >> I'm a little surprised about the it's using logical ino ioctl, not just >> TREE_SEARCH. >> >> I guess if we could get a plain tree search based one (it only search >> commit root, which is exactly balance based on), it would be easier to >> do the digging. >> >>> OSError: [Errno 22] Invalid argument >>> >>> root@tester:~# btrfs ins log 4368594108416 /media/testfs/ >>> /media/testfs//snap-1589258042/testhost/var/log/messages.6.lzma >>> /media/testfs//current/testhost/var/log/messages.6.lzma >>> /media/testfs//snap-1589249822/testhost/var/log/messages.6.lzma >>> ERROR: ino paths ioctl: No such file or directory >>> /media/testfs//snap-1589249547/testhost/var/log/messages.6.lzma >>> ERROR: ino paths ioctl: No such file or directory >>> /media/testfs//snap-1589248407/testhost/var/log/messages.6.lzma >>> /media/testfs//snap-1589256422/testhost/var/log/messages.6.lzma >>> ERROR: ino paths ioctl: No such file or directory >>> /media/testfs//snap-1589251322/testhost/var/log/messages.6.lzma >>> /media/testfs//snap-1589251682/testhost/var/log/messages.6.lzma >>> /media/testfs//snap-1589253842/testhost/var/log/messages.6.lzma >>> /media/testfs//snap-1589246727/testhost/var/log/messages.6.lzma >>> /media/testfs//snap-1589258582/testhost/var/log/messages.6.lzma >>> /media/testfs//snap-1589244027/testhost/var/log/messages.6.lzma >>> /media/testfs//snap-1589245227/testhost/var/log/messages.6.lzma >>> ERROR: ino paths ioctl: No such file or directory >>> ERROR: ino paths ioctl: No such file or directory >>> /media/testfs//snap-1589246127/testhost/var/log/messages.6.lzma >>> /media/testfs//snap-1589247327/testhost/var/log/messages.6.lzma >>> ERROR: ino paths ioctl: No such file or directory >>> >>> Hmmm, I wonder if there's a problem with deleted snapshots? >> >> Yes, also what I'm guessing. >> >> The cleanup of data reloc tree doesn't look correct to me. >> >> Thanks for the new clues, >> Qu >> >>> I have those >>> nearly continuously in my test environment, which is creating and deleting >>> snapshots all the time. >>> >>> root@tester:~# btrfs ins log 4368594108416 -P /media/testfs/ >>> inode 20838190 offset 0 root 10347 >>> inode 20838190 offset 0 root 8013 >>> inode 20838190 offset 0 root 10332 >>> inode 20838190 offset 0 root 10330 >>> inode 20838190 offset 0 root 10331 >>> inode 20838190 offset 0 root 10328 >>> inode 20838190 offset 0 root 10329 >>> inode 20838190 offset 0 root 10343 >>> inode 20838190 offset 0 root 10333 >>> inode 20838190 offset 0 root 10334 >>> inode 20838190 offset 0 root 10336 >>> inode 20838190 offset 0 root 10338 >>> inode 20838190 offset 0 root 10325 >>> inode 20838190 offset 0 root 10349 >>> inode 20838190 offset 0 root 10320 >>> inode 20838190 offset 0 root 10321 >>> inode 20838190 offset 0 root 10322 >>> inode 20838190 offset 0 root 10323 >>> inode 20838190 offset 0 root 10324 >>> inode 20838190 offset 0 root 10326 >>> inode 20838190 offset 0 root 10327 >>> root@tester:~# btrfs sub list -d /media/testfs/ >>> ID 10201 gen 1321166 top level 0 path DELETED >>> ID 10210 gen 1321166 top level 0 path DELETED >>> ID 10230 gen 1321166 top level 0 path DELETED >>> ID 10254 gen 1321166 top level 0 path DELETED >>> ID 10257 gen 1321166 top level 0 path DELETED >>> ID 10274 gen 1321166 top level 0 path DELETED >>> ID 10281 gen 1321166 top level 0 path DELETED >>> ID 10287 gen 1321166 top level 0 path DELETED >>> ID 10296 gen 1321166 top level 0 path DELETED >>> ID 10298 gen 1321166 top level 0 path DELETED >>> ID 10299 gen 1321166 top level 0 path DELETED >>> ID 10308 gen 1321166 top level 0 path DELETED >>> ID 10311 gen 1321166 top level 0 path DELETED >>> ID 10313 gen 1321166 top level 0 path DELETED >>> ID 10315 gen 1321166 top level 0 path DELETED >>> ID 10317 gen 1321166 top level 0 path DELETED >>> ID 10322 gen 1321166 top level 0 path DELETED >>> ID 10323 gen 1321166 top level 0 path DELETED >>> ID 10327 gen 1321166 top level 0 path DELETED >>> ID 10328 gen 1321166 top level 0 path DELETED >>> ID 10330 gen 1321166 top level 0 path DELETED >>> ID 10333 gen 1321166 top level 0 path DELETED >>> >>> >>>>> Thanks, >>>>> Qu >>>> >>>>> From 82f3b96a68561b2de9712262cb652192b8ea9b1b Mon Sep 17 00:00:00 2001 >>>>> From: Qu Wenruo >>>>> Date: Mon, 11 May 2020 16:27:43 +0800 >>>>> Subject: [PATCH] btrfs: Remove the REF_COW bit for data reloc tree >>>>> >>>>> Signed-off-by: Qu Wenruo >>>>> --- >>>>> fs/btrfs/disk-io.c | 9 ++++++++- >>>>> fs/btrfs/inode.c | 6 ++++-- >>>>> fs/btrfs/relocation.c | 3 ++- >>>>> 3 files changed, 14 insertions(+), 4 deletions(-) >>>>> >>>>> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c >>>>> index 56675d3cd23a..cb90966a8aab 100644 >>>>> --- a/fs/btrfs/disk-io.c >>>>> +++ b/fs/btrfs/disk-io.c >>>>> @@ -1418,9 +1418,16 @@ static int btrfs_init_fs_root(struct btrfs_root *root) >>>>> if (ret) >>>>> goto fail; >>>>> >>>>> - if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) { >>>>> + if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID && >>>>> + root->root_key.objectid != BTRFS_DATA_RELOC_TREE_OBJECTID) { >>>>> set_bit(BTRFS_ROOT_REF_COWS, &root->state); >>>>> btrfs_check_and_init_root_item(&root->root_item); >>>>> + } else if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID) { >>>>> + /* >>>>> + * Data reloc tree won't be snapshotted, thus it's COW only >>>>> + * tree, it's needed to set TRACK_DIRTY bit for it. >>>>> + */ >>>>> + set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state); >>>>> } >>>>> >>>>> btrfs_init_free_ino_ctl(root); >>>>> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c >>>>> index 5d567082f95a..71841535c7ca 100644 >>>>> --- a/fs/btrfs/inode.c >>>>> +++ b/fs/btrfs/inode.c >>>>> @@ -4129,7 +4129,8 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans, >>>>> * extent just the way it is. >>>>> */ >>>>> if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) || >>>>> - root == fs_info->tree_root) >>>>> + root == fs_info->tree_root || >>>>> + root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID) >>>>> btrfs_drop_extent_cache(BTRFS_I(inode), ALIGN(new_size, >>>>> fs_info->sectorsize), >>>>> (u64)-1, 0); >>>>> @@ -4334,7 +4335,8 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans, >>>>> >>>>> if (found_extent && >>>>> (test_bit(BTRFS_ROOT_REF_COWS, &root->state) || >>>>> - root == fs_info->tree_root)) { >>>>> + root == fs_info->tree_root || >>>>> + root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID)) { >>>>> struct btrfs_ref ref = { 0 }; >>>>> >>>>> bytes_deleted += extent_num_bytes; >>>>> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c >>>>> index f25deca18a5d..a85dd5d465f6 100644 >>>>> --- a/fs/btrfs/relocation.c >>>>> +++ b/fs/btrfs/relocation.c >>>>> @@ -1087,7 +1087,8 @@ int replace_file_extents(struct btrfs_trans_handle *trans, >>>>> * if we are modifying block in fs tree, wait for readpage >>>>> * to complete and drop the extent cache >>>>> */ >>>>> - if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) { >>>>> + if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID && >>>>> + root->root_key.objectid != BTRFS_DATA_RELOC_TREE_OBJECTID) { >>>>> if (first) { >>>>> inode = find_next_inode(root, key.objectid); >>>>> first = 0; >>>>> -- >>>>> 2.26.2 >>>>> >>>> >>>> >>>> >>>> >>> >>> >> > > >