Re: ext4 memory leak (was Re: [PATCH] x86: _edata should include all .data.* sections on X86_64)

Alexey Fisher
2009-07-15T08:54:23Z

This patch work for me.

Aneesh Kumar K.V schrieb:
> On Tue, Jul 14, 2009 at 01:26:30PM +0100, Catalin Marinas wrote:
>> (I cc'ed linux-ext4@vger.kernel.org as well)
>>
>> On Tue, 2009-07-14 at 12:37 +0200, Alexey Fisher wrote:
>>> this is complete trace from debug/kmemleak .
>> [...]
>>> i will compile now latest linux-arm.org/linux-2.6.git
>>> unreferenced object 0xffff880132c48890 (size 1024):
>>> comm "exe", pid 1612, jiffies 4294894130
>>> backtrace:
>>> [<ffffffff810fbaca>] create_object+0x13a/0x2c0
>>> [<ffffffff810fbd75>] kmemleak_alloc+0x25/0x60
>>> [<ffffffff810f596b>] __kmalloc+0x11b/0x210
>>> [<ffffffff811ae061>] ext4_mb_init+0x1b1/0x5c0
>>> [<ffffffff8119f1e9>] ext4_fill_super+0x1e29/0x2720
>>> [<ffffffff8110111f>] get_sb_bdev+0x16f/0x1b0
>>> [<ffffffff81195413>] ext4_get_sb+0x13/0x20
>>> [<ffffffff81100bf6>] vfs_kern_mount+0x76/0x180
>>> [<ffffffff81100d6d>] do_kern_mount+0x4d/0x120
>>> [<ffffffff81118ee7>] do_mount+0x307/0x8b0
>>> [<ffffffff8111951f>] sys_mount+0x8f/0xe0
>>> [<ffffffff8100b66b>] system_call_fastpath+0x16/0x1b
>>> [<ffffffffffffffff>] 0xffffffffffffffff
>> After some investigation, this looks to me like a real leak.
>>
>> I managed to reproduce something similar (though the size may differ, I
>> think depending on filesystem size - only tried with a 64MB loop
>> device):
>>
>> unreferenced object 0xde468300 (size 32):
>> comm "mount", pid 1445, jiffies 4294950074
>> backtrace:
>> [<c006d473>] __save_stack_trace+0x17/0x1c
>> [<c006d545>] create_object+0xcd/0x188
>> [<c01efe43>] kmemleak_alloc+0x1b/0x3c
>> [<c006c013>] __kmalloc+0xd7/0xe4
>> [<c00c1029>] ext4_mb_init+0x14d/0x374
>> [<c00b7d7d>] ext4_fill_super+0x1385/0x16b4
>> [<c0070891>] get_sb_bdev+0xa9/0xe4
>> [<c00b574b>] ext4_get_sb+0xf/0x14
>> [<c006fd3f>] vfs_kern_mount+0x33/0x64
>> [<c006fda5>] do_kern_mount+0x25/0x8c
>> [<c007e11f>] do_mount+0x47f/0x4c4
>> [<c007e1b5>] sys_mount+0x51/0x80
>> [<c0027c01>] ret_fast_syscall+0x1/0x40
>> [<ffffffff>] 0xffffffff
>>
>> The above block is the meta_group_info allocated in
>> ext4_mb_init_backend() and stored in sbi->s_group_info[i] (i = 0 in my
>> case). Adding printk's and and inspecting the memory at
>> sbi->s_group_info[] shows different value stored, not the pointer
>> reported as leak.
>>
>> About the new pointer at sbi->s_group_info[0], kmemleak has this
>> information (via the dump= option in my branch; it isn't a leak report):
>>
>> kmemleak: Object 0xdfebfa80 (size 128):
>> kmemleak: comm "mount", pid 1445, jiffies 4294950075
>> kmemleak: min_count = 1
>> kmemleak: count = 1
>> kmemleak: flags = 0x1
>> kmemleak: backtrace:
>> [<c006d473>] __save_stack_trace+0x17/0x1c
>> [<c006d545>] create_object+0xcd/0x188
>> [<c01efe43>] kmemleak_alloc+0x1b/0x3c
>> [<c006c013>] __kmalloc+0xd7/0xe4
>> [<c00c0df1>] ext4_mb_add_groupinfo+0x29/0x114
>> [<c00c107f>] ext4_mb_init+0x1a3/0x374
>> [<c00b7d7d>] ext4_fill_super+0x1385/0x16b4
>> [<c0070891>] get_sb_bdev+0xa9/0xe4
>> [<c00b574b>] ext4_get_sb+0xf/0x14
>> [<c006fd3f>] vfs_kern_mount+0x33/0x64
>> [<c006fda5>] do_kern_mount+0x25/0x8c
>> [<c007e11f>] do_mount+0x47f/0x4c4
>> [<c007e1b5>] sys_mount+0x51/0x80
>> [<c0027c01>] ret_fast_syscall+0x1/0x40
>> [<ffffffff>] 0xffffffff
>>
>> So, ext4_mb_add_groupinfo() is overriding the pointers stored in
>> sbi->s_group_info[] by the ext4_mb_init_backend() function without
>> freeing them first.
>>
>> Maybe the ext4 people could clarify what is happening here as I'm not
>> familiar with the code.
>>
>
> Can you try this patch ?
>
> commit 4cc505d4c16c86f8f590ce4b288c920572bf2be9
> Author: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> Date: Wed Jul 15 13:20:37 2009 +0530
>
> ext4: Memory leak fix ext4_group_info allocation.
>
> commit 5f21b0e642d7bf6fe4434c9ba12bc9cb96b17cf7 was done to
> reallocate groupinfo struct during resize properly. That goal
> was to allocate new groupinfo struct when we are adding new block
> groups during resize. Calling ext4_mb_add_group_info in the
> mballoc initialization code path resulted in we reallocating
> the group info struct . Fix this by not separately allocating
> group info in the mballoc init path and always depend on
> ext4_mb_add_group_info to allocate group info struct.
>
> The earlier code also had a bug that we allocated less number of
> group info struct for the last meta group. But on resize we
> expected that we had EXT4_DESC_PER_BLOCK group info struct for
> each meta group.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 519a0a6..96ed1d8 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2615,22 +2615,6 @@ static int ext4_mb_init_backend(struct super_block *sb)
> goto err_freesgi;
> }
> EXT4_I(sbi->s_buddy_cache)->i_disksize = 0;
> -
> - metalen = sizeof(*meta_group_info) << EXT4_DESC_PER_BLOCK_BITS(sb);
> - for (i = 0; i < num_meta_group_infos; i++) {
> - if ((i + 1) == num_meta_group_infos)
> - metalen = sizeof(*meta_group_info) *
> - (ngroups -
> - (i << EXT4_DESC_PER_BLOCK_BITS(sb)));
> - meta_group_info = kmalloc(metalen, GFP_KERNEL);
> - if (meta_group_info == NULL) {
> - printk(KERN_ERR "EXT4-fs: can't allocate mem for a "
> - "buddy group\n");
> - goto err_freemeta;
> - }
> - sbi->s_group_info[i] = meta_group_info;
> - }
> -
> for (i = 0; i < ngroups; i++) {
> desc = ext4_get_group_desc(sb, i, NULL);
> if (desc == NULL) {
>
>
>
> --
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