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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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6
fs/aio.c
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@ -103,6 +103,7 @@ static int aio_setup_ring(struct kioctx *ctx)
unsigned nr_events = ctx->max_reqs;
unsigned long size;
int nr_pages;
bool populate;
/* Compensate for the ring buffer's head/tail overlap entry */
nr_events += 2; /* 1 is required, 2 for good luck */
@ -129,7 +130,8 @@ static int aio_setup_ring(struct kioctx *ctx)
down_write(&ctx->mm->mmap_sem);
info->mmap_base = do_mmap_pgoff(NULL, 0, info->mmap_size,
PROT_READ|PROT_WRITE,
MAP_ANONYMOUS|MAP_PRIVATE, 0);
MAP_ANONYMOUS|MAP_PRIVATE, 0,
&populate);
if (IS_ERR((void *)info->mmap_base)) {
up_write(&ctx->mm->mmap_sem);
info->mmap_size = 0;
@ -147,6 +149,8 @@ static int aio_setup_ring(struct kioctx *ctx)
aio_free_ring(ctx);
return -EAGAIN;
}
if (populate)
mm_populate(info->mmap_base, info->mmap_size);
ctx->user_id = info->mmap_base;