diff options
| author | Andrea Righi <righi.andrea@gmail.com> | 2009-04-30 15:08:57 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-05-02 15:36:10 -0700 |
| commit | 9e4a5bda89034502fb144331e71a0efdfd5fae97 (patch) | |
| tree | 89706c956da4b6cddf04d60be736e8a05f3f2679 | |
| parent | 8713e01295140f674a41f2199b0f7ca99dfb69d5 (diff) | |
mm: prevent divide error for small values of vm_dirty_bytes
Avoid setting less than two pages for vm_dirty_bytes: this is necessary to
avoid potential division by 0 (like the following) in get_dirty_limits().
[ 49.951610] divide error: 0000 [#1] PREEMPT SMP
[ 49.952195] last sysfs file: /sys/devices/pci0000:00/0000:00:01.1/host0/target0:0:0/0:0:0:0/block/sda/uevent
[ 49.952195] CPU 1
[ 49.952195] Modules linked in: pcspkr
[ 49.952195] Pid: 3064, comm: dd Not tainted 2.6.30-rc3 #1
[ 49.952195] RIP: 0010:[<ffffffff802d39a9>] [<ffffffff802d39a9>] get_dirty_limits+0xe9/0x2c0
[ 49.952195] RSP: 0018:ffff88001de03a98 EFLAGS: 00010202
[ 49.952195] RAX: 00000000000000c0 RBX: ffff88001de03b80 RCX: 28f5c28f5c28f5c3
[ 49.952195] RDX: 0000000000000000 RSI: 00000000000000c0 RDI: 0000000000000000
[ 49.952195] RBP: ffff88001de03ae8 R08: 0000000000000000 R09: 0000000000000000
[ 49.952195] R10: ffff88001ddda9a0 R11: 0000000000000001 R12: 0000000000000001
[ 49.952195] R13: ffff88001fbc8218 R14: ffff88001de03b70 R15: ffff88001de03b78
[ 49.952195] FS: 00007fe9a435b6f0(0000) GS:ffff8800025d9000(0000) knlGS:0000000000000000
[ 49.952195] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 49.952195] CR2: 00007fe9a39ab000 CR3: 000000001de38000 CR4: 00000000000006e0
[ 49.952195] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 49.952195] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 49.952195] Process dd (pid: 3064, threadinfo ffff88001de02000, task ffff88001ddda250)
[ 49.952195] Stack:
[ 49.952195] ffff88001fa0de00 ffff88001f2dbd70 ffff88001f9fe800 000080b900000000
[ 49.952195] 00000000000000c0 ffff8800027a6100 0000000000000400 ffff88001fbc8218
[ 49.952195] 0000000000000000 0000000000000600 ffff88001de03bb8 ffffffff802d3ed7
[ 49.952195] Call Trace:
[ 49.952195] [<ffffffff802d3ed7>] balance_dirty_pages_ratelimited_nr+0x1d7/0x3f0
[ 49.952195] [<ffffffff80368f8e>] ? ext3_writeback_write_end+0x9e/0x120
[ 49.952195] [<ffffffff802cc7df>] generic_file_buffered_write+0x12f/0x330
[ 49.952195] [<ffffffff802cce8d>] __generic_file_aio_write_nolock+0x26d/0x460
[ 49.952195] [<ffffffff802cda32>] ? generic_file_aio_write+0x52/0xd0
[ 49.952195] [<ffffffff802cda49>] generic_file_aio_write+0x69/0xd0
[ 49.952195] [<ffffffff80365fa6>] ext3_file_write+0x26/0xc0
[ 49.952195] [<ffffffff803034d1>] do_sync_write+0xf1/0x140
[ 49.952195] [<ffffffff80290d1a>] ? get_lock_stats+0x2a/0x60
[ 49.952195] [<ffffffff80280730>] ? autoremove_wake_function+0x0/0x40
[ 49.952195] [<ffffffff8030411b>] vfs_write+0xcb/0x190
[ 49.952195] [<ffffffff803042d0>] sys_write+0x50/0x90
[ 49.952195] [<ffffffff8022ff6b>] system_call_fastpath+0x16/0x1b
[ 49.952195] Code: 00 00 00 2b 05 09 1c 17 01 48 89 c6 49 0f af f4 48 c1 ee 02 48 89 f0 48 f7 e1 48 89 d6 31 d2 48 c1 ee 02 48 0f af 75 d0 48 89 f0 <48> f7 f7 41 8b 95 ac 01 00 00 48 89 c7 49 0f af d4 48 c1 ea 02
[ 49.952195] RIP [<ffffffff802d39a9>] get_dirty_limits+0xe9/0x2c0
[ 49.952195] RSP <ffff88001de03a98>
[ 50.096523] ---[ end trace 008d7aa02f244d7b ]---
Signed-off-by: Andrea Righi <righi.andrea@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | Documentation/sysctl/vm.txt | 4 | ||||
| -rw-r--r-- | kernel/sysctl.c | 5 |
2 files changed, 8 insertions, 1 deletions
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index 97c4b328432..b716d33912d 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt @@ -90,6 +90,10 @@ will itself start writeback. If dirty_bytes is written, dirty_ratio becomes a function of its value (dirty_bytes / the amount of dirtyable system memory). +Note: the minimum value allowed for dirty_bytes is two pages (in bytes); any +value lower than this limit will be ignored and the old configuration will be +retained. + ============================================================== dirty_expire_centisecs diff --git a/kernel/sysctl.c b/kernel/sysctl.c index e3d2c7dd59b..ea78fa101ad 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -103,6 +103,9 @@ static unsigned long one_ul = 1; static int one_hundred = 100; static int one_thousand = 1000; +/* this is needed for the proc_doulongvec_minmax of vm_dirty_bytes */ +static unsigned long dirty_bytes_min = 2 * PAGE_SIZE; + /* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */ static int maxolduid = 65535; static int minolduid; @@ -1006,7 +1009,7 @@ static struct ctl_table vm_table[] = { .mode = 0644, .proc_handler = &dirty_bytes_handler, .strategy = &sysctl_intvec, - .extra1 = &one_ul, + .extra1 = &dirty_bytes_min, }, { .procname = "dirty_writeback_centisecs", |