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mm: introduce mm_populate() for populating new vmas

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When creating new mappings using the MAP_POPULATE / MAP_LOCKED flags (or
with MCL_FUTURE in effect), we want to populate the pages within the
newly created vmas.  This may take a while as we may have to read pages
from disk, so ideally we want to do this outside of the write-locked
mmap_sem region.

This change introduces mm_populate(), which is used to defer populating
such mappings until after the mmap_sem write lock has been released.
This is implemented as a generalization of the former do_mlock_pages(),
which accomplished the same task but was using during mlock() /
mlockall().

Signed-off-by: Michel Lespinasse <[email protected]>
Reported-by: Andy Lutomirski <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Tested-by: Andy Lutomirski <[email protected]>
Cc: Greg Ungerer <[email protected]>
Cc: David Howells <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Michel Lespinasse 2013-02-22 16:32:37 -08:00 • committed by Linus Torvalds
commit bebeb3d68b
7 changed files with 62 additions and 22 deletions
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17
mm/mlock.c
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@ -416,7 +416,14 @@ static int do_mlock(unsigned long start, size_t len, int on)
return error;
}
static int do_mlock_pages(unsigned long start, size_t len, int ignore_errors)
/*
* __mm_populate - populate and/or mlock pages within a range of address space.
*
* This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
* flags. VMAs must be already marked with the desired vm_flags, and
* mmap_sem must not be held.
*/
int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
{
struct mm_struct *mm = current->mm;
unsigned long end, nstart, nend;
@ -498,7 +505,7 @@ SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
error = do_mlock(start, len, 1);
up_write(&current->mm->mmap_sem);
if (!error)
error = do_mlock_pages(start, len, 0);
error = __mm_populate(start, len, 0);
return error;
}
@ -564,10 +571,8 @@ SYSCALL_DEFINE1(mlockall, int, flags)
capable(CAP_IPC_LOCK))
ret = do_mlockall(flags);
up_write(&current->mm->mmap_sem);
if (!ret && (flags & MCL_CURRENT)) {
/* Ignore errors */
do_mlock_pages(0, TASK_SIZE, 1);
}
if (!ret && (flags & MCL_CURRENT))
mm_populate(0, TASK_SIZE);
out:
return ret;
}