On Sat, May 12, 2012 at 5:13 AM, Hugh Dickins <hughd@xxxxxxxxxx> wrote:
> Now tmpfs supports hole-punching via fallocate(), switch madvise_remove()
> to use do_fallocate() instead of vmtruncate_range(): which extends
> madvise(,,MADV_REMOVE) support from tmpfs to ext4, ocfs2 and xfs.
>
> There is one more user of vmtruncate_range() in our tree, staging/android's
> ashmem_shrink(): convert it to use do_fallocate() too (but if its unpinned
> areas are already unmapped - I don't know - then it would do better to use
> shmem_truncate_range() directly).
I suspect shmem_truncate_range directly would be the right approach,
but am not totally sure.
Arve: Any thoughts?
Hugh: Do you have a git tree with this set available somewhere? I was
working on my own tmpfs support for FALLOC_FL_PUNCH_HOLE, along with
my volatile range work, so I'd like to rebase on top of your work
here.
thanks
-john
>
> Based-on-patch-by: Cong Wang <amwang@xxxxxxxxxx>
> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
> ---
> drivers/staging/android/ashmem.c | 8 +++++---
> mm/madvise.c | 15 +++++++--------
> 2 files changed, 12 insertions(+), 11 deletions(-)
>
> --- 3045N.orig/drivers/staging/android/ashmem.c 2012-05-05 10:42:33.564056626 -0700
> +++ 3045N/drivers/staging/android/ashmem.c 2012-05-05 10:46:25.692062478 -0700
> @@ -19,6 +19,7 @@
> #include <linux/module.h>
> #include <linux/file.h>
> #include <linux/fs.h>
> +#include <linux/falloc.h>
> #include <linux/miscdevice.h>
> #include <linux/security.h>
> #include <linux/mm.h>
> @@ -363,11 +364,12 @@ static int ashmem_shrink(struct shrinker
>
> mutex_lock(&ashmem_mutex);
> list_for_each_entry_safe(range, next, &ashmem_lru_list, lru) {
> - struct inode *inode = range->asma->file->f_dentry->d_inode;
> loff_t start = range->pgstart * PAGE_SIZE;
> - loff_t end = (range->pgend + 1) * PAGE_SIZE - 1;
> + loff_t end = (range->pgend + 1) * PAGE_SIZE;
>
> - vmtruncate_range(inode, start, end);
> + do_fallocate(range->asma->file,
> + FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
> + start, end - start);
> range->purged = ASHMEM_WAS_PURGED;
> lru_del(range);
>
> --- 3045N.orig/mm/madvise.c 2012-05-05 10:42:33.572056784 -0700
> +++ 3045N/mm/madvise.c 2012-05-05 10:46:25.692062478 -0700
> @@ -11,8 +11,10 @@
> #include <linux/mempolicy.h>
> #include <linux/page-isolation.h>
> #include <linux/hugetlb.h>
> +#include <linux/falloc.h>
> #include <linux/sched.h>
> #include <linux/ksm.h>
> +#include <linux/fs.h>
>
> /*
> * Any behaviour which results in changes to the vma->vm_flags needs to
> @@ -200,8 +202,7 @@ static long madvise_remove(struct vm_are
> struct vm_area_struct **prev,
> unsigned long start, unsigned long end)
> {
> - struct address_space *mapping;
> - loff_t offset, endoff;
> + loff_t offset;
> int error;
>
> *prev = NULL; /* tell sys_madvise we drop mmap_sem */
> @@ -217,16 +218,14 @@ static long madvise_remove(struct vm_are
> if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
> return -EACCES;
>
> - mapping = vma->vm_file->f_mapping;
> -
> offset = (loff_t)(start - vma->vm_start)
> + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
> - endoff = (loff_t)(end - vma->vm_start - 1)
> - + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
>
> - /* vmtruncate_range needs to take i_mutex */
> + /* filesystem's fallocate may need to take i_mutex */
> up_read(¤t->mm->mmap_sem);
> - error = vmtruncate_range(mapping->host, offset, endoff);
> + error = do_fallocate(vma->vm_file,
> + FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
> + offset, end - start);
> down_read(¤t->mm->mmap_sem);
> return error;
> }
> --
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