* ext4 errors with full filesystem
@ 2015-08-13 8:23 Olaf Hering
2015-08-14 2:42 ` Theodore Ts'o
0 siblings, 1 reply; 4+ messages in thread
From: Olaf Hering @ 2015-08-13 8:23 UTC (permalink / raw)
To: linux-ext4
I just got the output below in syslog with a full filesystem.
Should I be worried about inconsistent filesystem now, or is that just an
overly verbose message about ENOSPC? This is a 4.1.5 kernel.
Olaf
root@probook:/dist/iso/sles11 # wget -m -np 'http://cdn.novell.com/prot/La2AdJJ4-Ok~/SLED-11-SP4-DVD-i586-GM-DVD1.iso'
...
Cannot write to ‘cdn.novell.com/prot/La2AdJJ4-Ok~/SLED-11-SP4-DVD-i586-GM-DVD1.iso’ (No space left on device).
root@probook:/dist/iso/sles11 # Aug 13 10:13:35 probook.fritz.box kernel: EXT4-fs (sda5): Delayed block allocation failed for inode 15695873 at logical offset 1942120 with max blocks 221 with error 28
Aug 13 10:13:49 probook.fritz.box kernel: EXT4-fs (sda5): This should not happen!! Data will be lost
Aug 13 10:14:06 probook.fritz.box kernel: EXT4-fs (sda5): Total free blocks count 0
Aug 13 10:14:06 probook.fritz.box kernel: EXT4-fs (sda5): Free/Dirty block details
Aug 13 10:14:07 probook.fritz.box kernel: EXT4-fs (sda5): free_blocks=0
Aug 13 10:14:07 probook.fritz.box kernel: EXT4-fs (sda5): dirty_blocks=221
Aug 13 10:14:07 probook.fritz.box kernel: EXT4-fs (sda5): Block reservation details
Aug 13 10:14:08 probook.fritz.box kernel: EXT4-fs (sda5): i_reserved_data_blocks=221
Filesystem volume name: DBG1S82E_dist
Last mounted on: /dist
Filesystem UUID: 62c145ba-e2ba-4592-b355-7bba833fc396
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery sparse_super large_file
Filesystem flags: signed_directory_hash
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 33554432
Block count: 268433408
Reserved block count: 26843
Free blocks: 2038421
Free inodes: 32683679
First block: 0
Block size: 2048
Fragment size: 2048
Reserved GDT blocks: 512
Blocks per group: 16384
Fragments per group: 16384
Inodes per group: 2048
Inode blocks per group: 256
Filesystem created: Sun Nov 10 14:01:47 2013
Last mount time: Wed Aug 12 08:49:02 2015
Last write time: Wed Aug 12 08:49:02 2015
Mount count: 285
Maximum mount count: -1
Last checked: Tue Apr 22 09:12:00 2014
Check interval: 0 (<none>)
Lifetime writes: 4960 MB
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 28
Desired extra isize: 28
Journal inode: 8
Default directory hash: half_md4
Directory Hash Seed: 19e1770c-aa3c-4aba-8108-e9a5c8792e09
Journal backup: inode blocks
Journal features: journal_incompat_revoke
Journal size: 64M
Journal length: 32768
Journal sequence: 0x0006a56b
Journal start: 10216
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: ext4 errors with full filesystem
2015-08-13 8:23 ext4 errors with full filesystem Olaf Hering
@ 2015-08-14 2:42 ` Theodore Ts'o
2015-08-14 9:48 ` Olaf Hering
0 siblings, 1 reply; 4+ messages in thread
From: Theodore Ts'o @ 2015-08-14 2:42 UTC (permalink / raw)
To: Olaf Hering; +Cc: linux-ext4
On Thu, Aug 13, 2015 at 10:23:07AM +0200, Olaf Hering wrote:
>
> I just got the output below in syslog with a full filesystem.
> Should I be worried about inconsistent filesystem now, or is that just an
> overly verbose message about ENOSPC? This is a 4.1.5 kernel.
You don't need to worry about an inconsistent file system, but it's an
error that isn't supposed to to happen. The warning message indicates
that writes issued got a success return code, but for which ran out of
space, and so some number of pages got lost and couldn't be saved to
disk. We keep track of how many data blocks have been committed, and
we have a reserved amount of space for metadata blocks which _should_
be enough.
For more details, see:
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=27dd43854227bb0e6ab70129bd21b60d396db2e7
I'm curious about your workload. How big is your file system, and how
fragmented is your file system per e2freefrag? And how quickly was
various programs writing to the file system at the time when you ran
out of space, and what sort of files and what was the average size
that was getting dumped into the file system? Oh, and how much memory
did you have in your system?
Thanks,
- Ted
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: ext4 errors with full filesystem
2015-08-14 2:42 ` Theodore Ts'o
@ 2015-08-14 9:48 ` Olaf Hering
2015-08-14 15:51 ` Theodore Ts'o
0 siblings, 1 reply; 4+ messages in thread
From: Olaf Hering @ 2015-08-14 9:48 UTC (permalink / raw)
To: Theodore Ts'o; +Cc: linux-ext4
On Thu, Aug 13, Theodore Ts'o wrote:
> On Thu, Aug 13, 2015 at 10:23:07AM +0200, Olaf Hering wrote:
> >
> > I just got the output below in syslog with a full filesystem.
> > Should I be worried about inconsistent filesystem now, or is that just an
> > overly verbose message about ENOSPC? This is a 4.1.5 kernel.
>
> You don't need to worry about an inconsistent file system, but it's an
> error that isn't supposed to to happen. The warning message indicates
I ran fsck -f anyway. There was no lost+found, I think that was removed long ago
because it conflicted with tabcompletion (ls /dist/lo<tab>). Since there was no
space left fsck was unable to create it, I think:
/lost+found not found. Create<y>? yes
ext2fs_new_block: Could not allocate block in ext2 filesystem while trying to create /lost+found directory
Otherwise no errors reported.
> I'm curious about your workload. How big is your file system, and how
> fragmented is your file system per e2freefrag? And how quickly was
> various programs writing to the file system at the time when you ran
> out of space, and what sort of files and what was the average size
> that was getting dumped into the file system? Oh, and how much memory
> did you have in your system?
Meanwhile I removed some smaller files to gain some space:
root@probook:~ # df /dist
/dev/sda5 528336856 528142072 141098 100% /dist
root@probook:~ # e2freefrag /dev/disk/by-label/DBG1S82E_dist
Device: /dev/disk/by-label/DBG1S82E_dist
Blocksize: 2048 bytes
Total blocks: 268433408
Free blocks: 0 (0.0%)
Min. free extent: 2 KB
Max. free extent: 26108 KB
Avg. free extent: 1692 KB
Num. free extent: 115
HISTOGRAM OF FREE EXTENT SIZES:
Extent Size Range : Free extents Free Blocks Percent
2K... 4K- : 13 13 inf%
4K... 8K- : 10 21 inf%
8K... 16K- : 17 102 inf%
16K... 32K- : 12 129 inf%
32K... 64K- : 12 254 inf%
64K... 128K- : 6 295 inf%
128K... 256K- : 6 560 inf%
256K... 512K- : 2 359 inf%
512K... 1024K- : 5 1902 inf%
1M... 2M- : 8 5701 inf%
2M... 4M- : 9 12859 inf%
4M... 8M- : 9 27150 inf%
8M... 16M- : 4 24156 inf%
16M... 32M- : 2 23891 inf%
There was just wget writing the iso to it, it was downloaded with about
10MB/sec. The system has 8GB RAM.
Olaf
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: ext4 errors with full filesystem
2015-08-14 9:48 ` Olaf Hering
@ 2015-08-14 15:51 ` Theodore Ts'o
0 siblings, 0 replies; 4+ messages in thread
From: Theodore Ts'o @ 2015-08-14 15:51 UTC (permalink / raw)
To: Olaf Hering; +Cc: linux-ext4
On Fri, Aug 14, 2015 at 11:48:31AM +0200, Olaf Hering wrote:
>
> There was just wget writing the iso to it, it was downloaded with about
> 10MB/sec. The system has 8GB RAM.
How big was the iso file when the disk filled?
If it happens again, can you run the "extents -n" command in debugfs?
So for example, if /dev/mapper/closure-u1 is mounted on /u1, and the
file of interest is /u1/userdata.img, then do something like this:
# debugfs /dev/mapper/closure-u1
debugfs 1.43-WIP (29-Mar-2015)
debugfs: extents -n userdata.img
Level Entries Logical Physical Length Flags
0/ 2 1/ 1 0 - 2874363 33987 2874364
1/ 2 1/ 35 0 - 170082 33986 170083
1/ 2 2/ 35 170083 - 178210 6676480 8128
1/ 2 3/ 35 178211 - 201880 6690816 23670
1/ 2 4/ 35 201881 - 214186 6690817 12306
1/ 2 5/ 35 214187 - 233062 6729728 18876
1/ 2 6/ 35 233063 - 254071 6751276 21009
1/ 2 7/ 35 254072 - 261825 6753325 7754
1/ 2 8/ 35 261826 - 284741 6785024 22916
1/ 2 9/ 35 284742 - 292895 6785025 8154
1/ 2 10/ 35 292896 - 314550 6854591 21655
1/ 2 11/ 35 314551 - 326862 6883328 12312
1/ 2 12/ 35 326863 - 345619 6883329 18757
1/ 2 13/ 35 345620 - 361847 6918144 16228
1/ 2 14/ 35 361848 - 376184 6918145 14337
1/ 2 15/ 35 376185 - 401211 6952960 25027
1/ 2 16/ 35 401212 - 408188 6952961 6977
1/ 2 17/ 35 408189 - 430974 6987776 22786
1/ 2 18/ 35 430975 - 443383 6987777 12409
1/ 2 19/ 35 443384 - 462088 7024640 18705
1/ 2 20/ 35 462089 - 480253 7047168 18165
1/ 2 21/ 35 480254 - 490889 7047169 10636
1/ 2 22/ 35 490890 - 513854 7079936 22965
1/ 2 23/ 35 513855 - 520795 7079937 6941
1/ 2 24/ 35 520796 - 543539 7114752 22744
1/ 2 25/ 35 543540 - 555928 7114753 12389
1/ 2 26/ 35 555929 - 572655 7153664 16727
1/ 2 27/ 35 572656 - 584947 7153665 12292
1/ 2 28/ 35 584948 - 604327 7186432 19380
1/ 2 29/ 35 604328 - 625455 7211008 21128
1/ 2 30/ 35 625456 - 634370 7211009 8915
1/ 2 31/ 35 634371 - 656666 7243776 22296
1/ 2 32/ 35 656667 - 664518 7243777 7852
1/ 2 33/ 35 664519 - 685186 7278592 20668
1/ 2 34/ 35 685187 - 699514 7278593 14328
1/ 2 35/ 35 699515 - 2874363 7317504 2174849
>From the above can see that this 1.8G file uses 35 metadata blocks.
How many metadata blocks are needed depends on how fragmented the free
space is. Each of the metadata blocks can hold up to 340 extents.
Without the -n option, all of the leaf nodes of the extent tree will
be displayed, then you'll likely see a very wide variety of extent
sizes. For example:
2/ 2 116/340 187478 - 187478 6700118 - 6700118 1
2/ 2 117/340 187480 - 187484 6700120 - 6700124 5
2/ 2 118/340 187486 - 187486 6700126 - 6700126 1
2/ 2 119/340 187488 - 187576 6700128 - 6700216 89
2/ 2 120/340 187579 - 187601 6700219 - 6700241 23
2/ 2 121/340 187603 - 191477 6700243 - 6704117 3875
2/ 2 122/340 191482 - 191483 6704122 - 6704123 2
2/ 2 123/340 191486 - 191486 6704126 - 6704126 1
2/ 2 124/340 191491 - 191494 6704131 - 6704134 4
Last column is the extent size; extents of size 3875 are good.
Extents of size 1 are not so good, both in terms of requiring lots of
seeks when you read the file, and because it burns space in the extent
tree. (The maximum extent size is 32k blocks, BTW.)
By default, we reserve 4096 blocks for unexpected metadata blocks or
2% of the file system space, which ever number is smaller. 4096
metadata blocks is a lot of space. Each metadata block can hold 340
extents leaf entries, So even in the worst case, where the file system
free space is completely fragmented, that should still be enough space
for a bit over 5.3 GB of space.
So in order to trigger the problem, there would need to be more than
5.3GB of delayed allocation pages in the page cache, such that when
the writeback daemon force these pages to be written to the file file
system, we would start consuming enough of the metadata blocks that we
could burn through the 4096 block reserve. Since you have 8GB of
memory, this is possible if there weren't any other large programs
running.
Hmm, the other thing we can do is to disable delayed allocation when
the file system is both (a) close to full, and (b) highly fragmented.
Currenty we only do (a) for SMP kernels, because we use a percpu
counter to estimate the amount of free space. I suspect using some
algorithm that estimates fragmentation is the right approach, since
just increasing the number of reserved blocks, or disabling delalloc
when the free space drops below some absolute value, such as say 4 MB,
would impact how well ext4 works on smaller devices such as thumb
drives.
- Ted
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2015-08-14 2:42 ` Theodore Ts'o
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