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Message-ID: <20131210093528.23399.qmail@science.horizon.com>
Date: 10 Dec 2013 04:35:28 -0500
From: "George Spelvin" <linux@...izon.com>
To: jack@...e.cz
Cc: linux@...izon.com, linux-ext4@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
tytso@....edu, viro@...IV.linux.org.uk
Subject: Re: 3.11.4: kernel BUG at fs/buffer.c:1268
One of those additional WARN_ON tests tripped, hooray!
And it turned out to be in the ext4 metadata checksumming. To be
precise, ext4_block_bitmap_csum_set() returned with irqs disabled,
and kaboom.
Since I have this experimental feature turned on and most people don't,
this explains why I'm finding it and World+Dog aren't.
I appear to be the designated finder of ext4 metadata_csum bugs, so tytso
notified on general principles. I dropped the generic linux-fsdevel
list from the Cc: list.
But looking at the code, it just calls into the linux-crypto layer and
Tim Chen's SSE CRC32C implementation which uses kernel_fpu_begin()
and kernel_fpu_end() if the block is large enough.
I was going to add and Herbert Xu and Tim Chen and all those mailing
lists, but looking at the code, it sure *looks* like they're Doing The
right Thing, so I'm holding off for a bit.
I'm not sure quite where to pass th buck on this one.
Relevant platform info:
- Intel i7-2700K processor, with SSE4.2 and thus the CRC32C instruction.
- CONFIG_PREEMPT_VOLUNTARY=y
- # CONFIG_PREEMPT_NONE is not set
- CONFIG_PREEMPT_VOLUNTARY=y
- # CONFIG_PREEMPT is not set
- CONFIG_PREEMPT_COUNT=y
- CONFIG_DEBUG_ATOMIC_SLEEP=y
- CONFIG_DEBUG_BUGVERBOSE=y
[475059.561544] ------------[ cut here ]------------
[475059.561553] WARNING: CPU: 4 PID: 24642 at fs/ext4/mballoc.c:4796 ext4_free_blocks+0xb77/0xc10()
[475059.561554] Modules linked in: fuse pl2303 ftdi_sio usbserial iTCO_wdt
[475059.561560] CPU: 4 PID: 24642 Comm: iceweasel Not tainted 3.11.5-00010-g5626386 #101
[475059.561561] Hardware name: Gigabyte Technology Co., Ltd. Z68A-D3H-B3/Z68A-D3H-B3, BIOS F13 03/20/2012
[475059.561562] 0000000000000009 ffff880204e99970 ffffffff8156050d 0000000000000000
[475059.561565] ffff880204e999a8 ffffffff81044103 ffff88021fb9b360 ffff8800a809eb60
[475059.561567] ffff880168efda20 ffff88021667f000 ffff88021610fec0 ffff880204e999b8
[475059.561569] Call Trace:
[475059.561573] [<ffffffff8156050d>] dump_stack+0x54/0x74
[475059.561576] [<ffffffff81044103>] warn_slowpath_common+0x73/0x90
[475059.561578] [<ffffffff810441d5>] warn_slowpath_null+0x15/0x20
[475059.561580] [<ffffffff81197da7>] ext4_free_blocks+0xb77/0xc10
[475059.561582] [<ffffffff8118bfd6>] ext4_ext_remove_space+0x806/0xe20
[475059.561585] [<ffffffff8119e3c4>] ? ext4_es_free_extent+0x54/0x60
[475059.561587] [<ffffffff8118e2b8>] ext4_ext_truncate+0xb8/0xe0
[475059.561590] [<ffffffff81174705>] ext4_truncate+0x2b5/0x300
[475059.561592] [<ffffffff811751b8>] ext4_evict_inode+0x3f8/0x430
[475059.561596] [<ffffffff8111aa4a>] evict+0xba/0x1c0
[475059.561598] [<ffffffff8111b3fb>] iput+0x10b/0x1b0
[475059.561600] [<ffffffff81117208>] dput+0x278/0x350
[475059.561604] [<ffffffff8110308a>] __fput+0x16a/0x240
[475059.561606] [<ffffffff81103199>] ____fput+0x9/0x10
[475059.561609] [<ffffffff8105e57c>] task_work_run+0x9c/0xd0
[475059.561612] [<ffffffff810454a7>] do_exit+0x2a7/0x9d0
[475059.561615] [<ffffffff8104fb6e>] ? __sigqueue_free.part.13+0x2e/0x40
[475059.561618] [<ffffffff81046a4e>] do_group_exit+0x3e/0xb0
[475059.561620] [<ffffffff810529e0>] get_signal_to_deliver+0x1b0/0x5f0
[475059.561623] [<ffffffff81002113>] do_signal+0x43/0x940
[475059.561626] [<ffffffff81051938>] ? do_send_sig_info+0x58/0x80
[475059.561628] [<ffffffff81002a6d>] do_notify_resume+0x5d/0x80
[475059.561632] [<ffffffff81568420>] int_signal+0x12/0x17
[475059.561633] ---[ end trace b093418eaa9338ce ]---
[475059.561635] ------------[ cut here ]------------
[475059.561637] WARNING: CPU: 4 PID: 24642 at fs/ext4/mballoc.c:4798 ext4_free_blocks+0xb61/0xc10()
[475059.561638] Modules linked in: fuse pl2303 ftdi_sio usbserial iTCO_wdt
[475059.561642] CPU: 4 PID: 24642 Comm: iceweasel Tainted: G W 3.11.5-00010-g5626386 #101
[475059.561644] Hardware name: Gigabyte Technology Co., Ltd. Z68A-D3H-B3/Z68A-D3H-B3, BIOS F13 03/20/2012
[475059.561644] 0000000000000009 ffff880204e99970 ffffffff8156050d 0000000000000000
[475059.561647] ffff880204e999a8 ffffffff81044103 ffff88021fb9b360 ffff8800a809eb60
[475059.561649] ffff880168efda20 ffff88021667f000 ffff88021610fec0 ffff880204e999b8
[475059.561651] Call Trace:
[475059.561654] [<ffffffff8156050d>] dump_stack+0x54/0x74
[475059.561656] [<ffffffff81044103>] warn_slowpath_common+0x73/0x90
[475059.561658] [<ffffffff810441d5>] warn_slowpath_null+0x15/0x20
[475059.561660] [<ffffffff81197d91>] ext4_free_blocks+0xb61/0xc10
[475059.561662] [<ffffffff8118bfd6>] ext4_ext_remove_space+0x806/0xe20
[475059.561665] [<ffffffff8119e3c4>] ? ext4_es_free_extent+0x54/0x60
[475059.561667] [<ffffffff8118e2b8>] ext4_ext_truncate+0xb8/0xe0
[475059.561669] [<ffffffff81174705>] ext4_truncate+0x2b5/0x300
[475059.561672] [<ffffffff811751b8>] ext4_evict_inode+0x3f8/0x430
[475059.561674] [<ffffffff8111aa4a>] evict+0xba/0x1c0
[475059.561675] [<ffffffff8111b3fb>] iput+0x10b/0x1b0
[475059.561677] [<ffffffff81117208>] dput+0x278/0x350
[475059.561679] [<ffffffff8110308a>] __fput+0x16a/0x240
[475059.561681] [<ffffffff81103199>] ____fput+0x9/0x10
[475059.561684] [<ffffffff8105e57c>] task_work_run+0x9c/0xd0
[475059.561686] [<ffffffff810454a7>] do_exit+0x2a7/0x9d0
[475059.561688] [<ffffffff8104fb6e>] ? __sigqueue_free.part.13+0x2e/0x40
[475059.561691] [<ffffffff81046a4e>] do_group_exit+0x3e/0xb0
[475059.561693] [<ffffffff810529e0>] get_signal_to_deliver+0x1b0/0x5f0
[475059.561695] [<ffffffff81002113>] do_signal+0x43/0x940
[475059.561697] [<ffffffff81051938>] ? do_send_sig_info+0x58/0x80
[475059.561700] [<ffffffff81002a6d>] do_notify_resume+0x5d/0x80
[475059.561702] [<ffffffff81568420>] int_signal+0x12/0x17
[475059.561704] ---[ end trace b093418eaa9338cf ]---
[475059.561705] ------------[ cut here ]------------
[475059.561708] WARNING: CPU: 4 PID: 24642 at fs/ext4/mballoc.c:4800 ext4_free_blocks+0xad0/0xc10()
[475059.561709] Modules linked in: fuse pl2303 ftdi_sio usbserial iTCO_wdt
[475059.561713] CPU: 4 PID: 24642 Comm: iceweasel Tainted: G W 3.11.5-00010-g5626386 #101
[475059.561714] Hardware name: Gigabyte Technology Co., Ltd. Z68A-D3H-B3/Z68A-D3H-B3, BIOS F13 03/20/2012
[475059.561715] 0000000000000009 ffff880204e99970 ffffffff8156050d 0000000000000000
[475059.561717] ffff880204e999a8 ffffffff81044103 ffff88021fb9b360 ffff8800a809eb60
[475059.561720] ffff880168efda20 ffff88021667f000 ffff88021610fec0 ffff880204e999b8
[475059.561723] Call Trace:
[475059.561726] [<ffffffff8156050d>] dump_stack+0x54/0x74
[475059.561728] [<ffffffff81044103>] warn_slowpath_common+0x73/0x90
[475059.561730] [<ffffffff810441d5>] warn_slowpath_null+0x15/0x20
[475059.561733] [<ffffffff81197d00>] ext4_free_blocks+0xad0/0xc10
[475059.561735] [<ffffffff8118bfd6>] ext4_ext_remove_space+0x806/0xe20
[475059.561738] [<ffffffff8119e3c4>] ? ext4_es_free_extent+0x54/0x60
[475059.561740] [<ffffffff8118e2b8>] ext4_ext_truncate+0xb8/0xe0
[475059.561742] [<ffffffff81174705>] ext4_truncate+0x2b5/0x300
[475059.561745] [<ffffffff811751b8>] ext4_evict_inode+0x3f8/0x430
[475059.561747] [<ffffffff8111aa4a>] evict+0xba/0x1c0
[475059.561748] [<ffffffff8111b3fb>] iput+0x10b/0x1b0
[475059.561750] [<ffffffff81117208>] dput+0x278/0x350
[475059.561753] [<ffffffff8110308a>] __fput+0x16a/0x240
[475059.561755] [<ffffffff81103199>] ____fput+0x9/0x10
[475059.561757] [<ffffffff8105e57c>] task_work_run+0x9c/0xd0
[475059.561760] [<ffffffff810454a7>] do_exit+0x2a7/0x9d0
[475059.561762] [<ffffffff8104fb6e>] ? __sigqueue_free.part.13+0x2e/0x40
[475059.561765] [<ffffffff81046a4e>] do_group_exit+0x3e/0xb0
[475059.561767] [<ffffffff810529e0>] get_signal_to_deliver+0x1b0/0x5f0
[475059.561768] [<ffffffff81002113>] do_signal+0x43/0x940
[475059.561770] [<ffffffff81051938>] ? do_send_sig_info+0x58/0x80
[475059.561771] [<ffffffff81002a6d>] do_notify_resume+0x5d/0x80
[475059.561773] [<ffffffff81568420>] int_signal+0x12/0x17
[475059.561774] ---[ end trace b093418eaa9338d0 ]---
[475059.561775] BUG: sleeping function called from invalid context at fs/ext4/mballoc.c:4802
[475059.561776] in_atomic(): 0, irqs_disabled(): 1, pid: 24642, name: iceweasel
[475059.561778] CPU: 4 PID: 24642 Comm: iceweasel Tainted: G W 3.11.5-00010-g5626386 #101
[475059.561779] Hardware name: Gigabyte Technology Co., Ltd. Z68A-D3H-B3/Z68A-D3H-B3, BIOS F13 03/20/2012
[475059.561779] ffff8800a809eb60 ffff880204e999a8 ffffffff8156050d 0000000000000079
[475059.561781] ffff880204e999b8 ffffffff81069faf ffff880204e99a90 ffffffff811977c0
[475059.561783] ffff880131ba3b58 ffff880204e99fd8 0000000104e999f8 00000000008de1f9
[475059.561784] Call Trace:
[475059.561786] [<ffffffff8156050d>] dump_stack+0x54/0x74
[475059.561789] [<ffffffff81069faf>] __might_sleep+0xcf/0xf0
[475059.561791] [<ffffffff811977c0>] ext4_free_blocks+0x590/0xc10
[475059.561793] [<ffffffff8118bfd6>] ext4_ext_remove_space+0x806/0xe20
[475059.561795] [<ffffffff8119e3c4>] ? ext4_es_free_extent+0x54/0x60
[475059.561796] [<ffffffff8118e2b8>] ext4_ext_truncate+0xb8/0xe0
[475059.561798] [<ffffffff81174705>] ext4_truncate+0x2b5/0x300
[475059.561800] [<ffffffff811751b8>] ext4_evict_inode+0x3f8/0x430
[475059.561801] [<ffffffff8111aa4a>] evict+0xba/0x1c0
[475059.561803] [<ffffffff8111b3fb>] iput+0x10b/0x1b0
[475059.561804] [<ffffffff81117208>] dput+0x278/0x350
[475059.561806] [<ffffffff8110308a>] __fput+0x16a/0x240
[475059.561807] [<ffffffff81103199>] ____fput+0x9/0x10
[475059.561809] [<ffffffff8105e57c>] task_work_run+0x9c/0xd0
[475059.561811] [<ffffffff810454a7>] do_exit+0x2a7/0x9d0
[475059.561812] [<ffffffff8104fb6e>] ? __sigqueue_free.part.13+0x2e/0x40
[475059.561814] [<ffffffff81046a4e>] do_group_exit+0x3e/0xb0
[475059.561816] [<ffffffff810529e0>] get_signal_to_deliver+0x1b0/0x5f0
[475059.561818] [<ffffffff81002113>] do_signal+0x43/0x940
[475059.561821] [<ffffffff81051938>] ? do_send_sig_info+0x58/0x80
[475059.561823] [<ffffffff81002a6d>] do_notify_resume+0x5d/0x80
[475059.561825] [<ffffffff81568420>] int_signal+0x12/0x17
[475059.561830] ------------[ cut here ]------------
[475059.561847] kernel BUG at fs/buffer.c:1268!
[475059.561860] invalid opcode: 0000 [#1] SMP
[475059.561873] Modules linked in: fuse pl2303 ftdi_sio usbserial iTCO_wdt
[475059.561897] CPU: 4 PID: 24642 Comm: iceweasel Tainted: G W 3.11.5-00010-g5626386 #101
[475059.561919] Hardware name: Gigabyte Technology Co., Ltd. Z68A-D3H-B3/Z68A-D3H-B3, BIOS F13 03/20/2012
[475059.561942] task: ffff880216684380 ti: ffff880204e98000 task.ti: ffff880204e98000
[475059.561961] RIP: 0010:[<ffffffff8155fa34>] [<ffffffff8155fa34>] check_irqs_on.part.16+0x4/0x6
[475059.561987] RSP: 0018:ffff880204e99798 EFLAGS: 00210046
[475059.562001] RAX: 0000000000200082 RBX: ffff880204e99928 RCX: ffff8802160fb000
[475059.562019] RDX: 0000000000001000 RSI: 000000000038005b RDI: ffff8802170f4ac0
[475059.562038] RBP: ffff880204e99798 R08: 0000000000000000 R09: 0000000000000000
[475059.562056] R10: ffff8802160fb000 R11: ffff880204e9951e R12: ffff8802170f4ac0
[475059.562079] R13: 0000000000001000 R14: ffff88021fbdbe00 R15: ffff88021667f000
[475059.562097] FS: 0000000000000000(0000) GS:ffff88021fb00000(0000) knlGS:0000000000000000
[475059.562118] CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033
[475059.562134] CR2: 0000000099d3b000 CR3: 000000000180c000 CR4: 00000000000407e0
[475059.562152] Stack:
[475059.562158] ffff880204e99808 ffffffff8112e2b7 ffff880204e997b0 0000000000200092
[475059.562181] ffffffff81568420 ffffffff81732ff4 ffffffff81568420 ffffffff8109861d
[475059.562208] 00000000ff8b8e44 ffff880204e997f0 ffff880204e99928 ffff8802170f4ac0
[475059.562231] Call Trace:
[475059.562241] [<ffffffff8112e2b7>] __find_get_block+0x1d7/0x1e0
[475059.562257] [<ffffffff81568420>] ? int_signal+0x12/0x17
[475059.562272] [<ffffffff81568420>] ? int_signal+0x12/0x17
[475059.562289] [<ffffffff8109861d>] ? __module_text_address+0xd/0x60
[475059.562306] [<ffffffff8112e2e0>] __getblk+0x20/0x2f0
[475059.562324] [<ffffffff8116fbb6>] __ext4_get_inode_loc+0x106/0x410
[475059.562347] [<ffffffff81171b68>] ext4_get_inode_loc+0x18/0x20
[475059.562363] [<ffffffff81173311>] ext4_reserve_inode_write+0x21/0x90
[475059.562380] [<ffffffff811733c9>] ext4_mark_inode_dirty+0x49/0x1a0
[475059.562397] [<ffffffff81175e4b>] ext4_dirty_inode+0x3b/0x60
[475059.562413] [<ffffffff81127aad>] __mark_inode_dirty+0x2d/0x230
[475059.562430] [<ffffffff81197a7c>] ext4_free_blocks+0x84c/0xc10
[475059.562447] [<ffffffff8118bfd6>] ext4_ext_remove_space+0x806/0xe20
[475059.562464] [<ffffffff8119e3c4>] ? ext4_es_free_extent+0x54/0x60
[475059.562480] [<ffffffff8118e2b8>] ext4_ext_truncate+0xb8/0xe0
[475059.562497] [<ffffffff81174705>] ext4_truncate+0x2b5/0x300
[475059.562512] [<ffffffff811751b8>] ext4_evict_inode+0x3f8/0x430
[475059.562528] [<ffffffff8111aa4a>] evict+0xba/0x1c0
[475059.562542] [<ffffffff8111b3fb>] iput+0x10b/0x1b0
[475059.562555] [<ffffffff81117208>] dput+0x278/0x350
[475059.562573] [<ffffffff8110308a>] __fput+0x16a/0x240
[475059.563369] [<ffffffff81103199>] ____fput+0x9/0x10
[475059.564164] [<ffffffff8105e57c>] task_work_run+0x9c/0xd0
[475059.564939] [<ffffffff810454a7>] do_exit+0x2a7/0x9d0
[475059.565728] [<ffffffff8104fb6e>] ? __sigqueue_free.part.13+0x2e/0x40
[475059.566518] [<ffffffff81046a4e>] do_group_exit+0x3e/0xb0
[475059.567296] [<ffffffff810529e0>] get_signal_to_deliver+0x1b0/0x5f0
[475059.568087] [<ffffffff81002113>] do_signal+0x43/0x940
[475059.568895] [<ffffffff81051938>] ? do_send_sig_info+0x58/0x80
[475059.569812] [<ffffffff81002a6d>] do_notify_resume+0x5d/0x80
[475059.570907] [<ffffffff81568420>] int_signal+0x12/0x17
[475059.572011] Code: 4d 85 e4 74 1d 41 80 44 24 58 01 65 48 8b 04 25 b0 b7 00 00 ff 88 44 e0 ff ff 4c 89 e7 e8 65 75 bb ff 5b 41 5c 5d c3 55 48 89 e5 <0f> 0b 55 48 89 e5 0f 0b 55 48 89 e5 0f 0b 55 48 89 e5 0f 0b 55
[475059.573325] RIP [<ffffffff8155fa34>] check_irqs_on.part.16+0x4/0x6
[475059.574581] RSP <ffff880204e99798>
[475059.583933] ---[ end trace b093418eaa9338d1 ]---
[475059.583936] Fixing recursive fault but reboot is needed!
For a reminder, here's the second debug patch:
commit 5626386a9d37c990977a12f833d6e6fc2e89d8bf
Author: Jan Kara <jack@...e.cz>
Date: Thu Nov 28 15:36:53 2013 +0100
Debug irqs
Signed-off-by: Jan Kara <jack@...e.cz>
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index e6f0d6b..ece38b4 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4760,8 +4760,11 @@ do_more:
might_sleep();
ext4_lock_group(sb, block_group);
+ WARN_ON(irqs_disabled());
mb_clear_bits(bitmap_bh->b_data, bit, count_clusters);
+ WARN_ON(irqs_disabled());
ext4_mb_free_metadata(handle, &e4b, new_entry);
+ WARN_ON(irqs_disabled());
} else {
/* need to update group_info->bb_free and bitmap
* with group lock held. generate_buddy look at
@@ -4778,15 +4781,23 @@ do_more:
might_sleep();
ext4_lock_group(sb, block_group);
+ WARN_ON(irqs_disabled());
mb_clear_bits(bitmap_bh->b_data, bit, count_clusters);
+ WARN_ON(irqs_disabled());
mb_free_blocks(inode, &e4b, bit, count_clusters);
+ WARN_ON(irqs_disabled());
}
ret = ext4_free_group_clusters(sb, gdp) + count_clusters;
+ WARN_ON(irqs_disabled());
ext4_free_group_clusters_set(sb, gdp, ret);
+ WARN_ON(irqs_disabled());
ext4_block_bitmap_csum_set(sb, block_group, gdp, bitmap_bh);
+ WARN_ON(irqs_disabled()); /***### BUG HERE ###***/
ext4_group_desc_csum_set(sb, block_group, gdp);
+ WARN_ON(irqs_disabled());
ext4_unlock_group(sb, block_group);
+ WARN_ON(irqs_disabled());
percpu_counter_add(&sbi->s_freeclusters_counter, count_clusters);
might_sleep();
The problem is metadata_csum enabled on this file system:
Filesystem volume name: root
Last mounted on: /
Filesystem UUID: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery extent flex_bg sparse_super large_file huge_file dir_nlink extra_isize metadata_csum
Filesystem flags: signed_directory_hash
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 1049600
Block count: 10485744
Reserved block count: 524287
Free blocks: 6196830
Free inodes: 727373
First block: 0
Block size: 4096
Fragment size: 4096
Reserved GDT blocks: 1021
Blocks per group: 32768
Fragments per group: 32768
Inodes per group: 3280
Inode blocks per group: 205
Flex block group size: 16
Filesystem created: Mon Oct 7 23:15:31 2013
Last mount time: Tue Dec 10 01:02:40 2013
Last write time: Tue Dec 10 01:02:40 2013
Mount count: 2
Maximum mount count: -1
Last checked: Wed Dec 4 12:46:49 2013
Check interval: 0 (<none>)
Lifetime writes: 155 GB
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
First orphan inode: 735089
Default directory hash: half_md4
Directory Hash Seed: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
Journal backup: inode blocks
Checksum type: crc32c
Checksum: 0xfeaba085
Journal features: journal_incompat_revoke
Journal size: 128M
Journal length: 32768
Journal sequence: 0x0004373b
Journal start: 22384
Looking at what happens where,
ext4_block_bitmap_csum_set() is a simple wrapper around ext4_chksum:
=== fs/ext4/bitmap.c:86 ==
void ext4_block_bitmap_csum_set(struct super_block *sb, ext4_group_t group,
struct ext4_group_desc *gdp,
struct buffer_head *bh)
{
int sz = EXT4_CLUSTERS_PER_GROUP(sb) / 8;
__u32 csum;
struct ext4_sb_info *sbi = EXT4_SB(sb);
if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
return;
csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)bh->b_data, sz);
gdp->bg_block_bitmap_csum_lo = cpu_to_le16(csum & 0xFFFF);
if (sbi->s_desc_size >= EXT4_BG_BLOCK_BITMAP_CSUM_HI_END)
gdp->bg_block_bitmap_csum_hi = cpu_to_le16(csum >> 16);
}
which in turn calls only crypto_shash_update:
=== fs/ext4/ext4.h:1701 ==
static inline u32 ext4_chksum(struct ext4_sb_info *sbi, u32 crc,
const void *address, unsigned int length)
{
struct {
struct shash_desc shash;
char ctx[4];
} desc;
int err;
BUG_ON(crypto_shash_descsize(sbi->s_chksum_driver)!=sizeof(desc.ctx));
desc.shash.tfm = sbi->s_chksum_driver;
desc.shash.flags = 0;
*(u32 *)desc.ctx = crc;
err = crypto_shash_update(&desc.shash, address, length);
BUG_ON(err);
return *(u32 *)desc.ctx;
}
=== crypto/shash.c:97 ===
int crypto_shash_update(struct shash_desc *desc, const u8 *data,
unsigned int len)
{
struct crypto_shash *tfm = desc->tfm;
struct shash_alg *shash = crypto_shash_alg(tfm);
unsigned long alignmask = crypto_shash_alignmask(tfm);
if ((unsigned long)data & alignmask)
return shash_update_unaligned(desc, data, len);
return shash->update(desc, data, len);
}
=== Discussion ===
desc.shash.tfm is filled in from sbi->s_chksum_driver, which is filled in at
ext4_fill_super() time by crypto_alloc_shash("crc32c", 0, 0).
Thus, shash->update should turn into a call to crypto/crc32c.c:chksum_update(),
which calls lib/crc32.c:__crc32c_le().
Now, I happen to be running an i7-2700k which has sse4_2, and thus calls
into the x86 specific code, and apparently for large blocks it uses PCLMULQDQ,
which requires kernel_fpu_begin/end.
At least that makes some degree of sense. The low level code, though
uses the functions in a very simple way that I can't see how it could fail
to unlock at the end.
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