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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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12
ipc/shm.c
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@ -967,11 +967,11 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
unsigned long flags;
unsigned long prot;
int acc_mode;
unsigned long user_addr;
struct ipc_namespace *ns;
struct shm_file_data *sfd;
struct path path;
fmode_t f_mode;
bool populate = false;
err = -EINVAL;
if (shmid < 0)
@ -1070,13 +1070,15 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
goto invalid;
}
user_addr = do_mmap_pgoff(file, addr, size, prot, flags, 0);
*raddr = user_addr;
addr = do_mmap_pgoff(file, addr, size, prot, flags, 0, &populate);
*raddr = addr;
err = 0;
if (IS_ERR_VALUE(user_addr))
err = (long)user_addr;
if (IS_ERR_VALUE(addr))
err = (long)addr;
invalid:
up_write(&current->mm->mmap_sem);
if (populate)
mm_populate(addr, size);
out_fput:
fput(file);