working of migrate_page (exported) function in mm/migrate.c linux Kernel

ajay saini ajay_saini1006 at
Sun Sep 22 23:21:46 EDT 2013


I have read some of these uses (of migrate_page) from linux kernel source code and tried to use this function in my kernel module.
But it somehow hangs my module.

Linux version : 2.6 and system has 4 NUMA nodes (0-3) and has 16 cores in total.

I have done following: ( I already have a pointer to old page as pg )  [ this code is somewhat taken from usage of "migrate_page" in mm/migrate.c file ]
struct page *new_page = alloc_pages_exact_node(2,GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0);
if ( new_page != NULL )
    if ( trylock_page(new_page) )
          new_page->index   = pg->index;
          new_page->mapping = pg->mapping;
          struct address_space *mapping = pg->mapping;
          migrate_page(mapping, new_page, pg);
- I have checked without locking also, but it does not work

- I check the existence of both pages and on what NUMA node they are assigned and it gives me correct information. It is only when I make a call to  migrate_page does the code hangs.

Any ideas?


 From: "Valdis.Kletnieks at" <Valdis.Kletnieks at>
To: ajay saini <ajay_saini1006 at> 
Cc: "kernelnewbies at" <kernelnewbies at> 
Sent: Sunday, 22 September 2013 9:53 PM
Subject: Re: working of migrate_page (exported) function in mm/migrate.c linux	Kernel

On Mon, 23 Sep 2013 09:00:21 +0800, ajay saini said:
> Is it used somewhere ?

[~] cd /usr/src/linux-next/
[/usr/src/linux-next] find [a-z]* -name '*.[ch]' | xargs grep migrate_page | grep -v migrate_pages

And start searching from there.  You'll probably have to iterate several
times, because there's at least onea few lines of the form:

mm/swap_state.c:        .migratepage    = migrate_page,
mm/shmem.c:     .migratepage    = migrate_page,

which means you need to figure out who calls that function pointer.

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