On 03/03/2012 10:02 PM, Naoya Horiguchi wrote:
On Thu, Mar 01, 2012 at 09:58:41PM -0500, Steven Truelove wrote:
When calling shmget() with SHM_HUGETLB, shmget aligns the request size to PAGE_SIZE, but this is not sufficient. Modified hugetlb_file_setup() to align requests to the huge page size, and to accept an address argument so that all alignment checks can be performed in hugetlb_file_setup(), rather than in its callers. Changed newseg and mmap_pgoff to match new prototype and eliminated a now redundant alignment check.
I think only rounding up request size in shmget() is not sufficient,
because later shmat() also have alignment check and fails to mmap()
to unaligned address.
Maybe file->f_op->get_unmapped_area() (or hugetlb_get_unmapped_area())
should have round up code, I think.
Could you try it?
Because the allocation is done in shmget() and the the address is not
provided until shmat(), I don't see a way to make this work reasonably.
I would argue that only allowing aligned addresses, or allowing the
kernel to choose the address, is a reasonable restriction on SHM_HUGETLB
usage.
Regarding your other comments, I will submit a revised patch.
Thanks,
Steven Truelove
And a few comments below,
Signed-off-by: Steven Truelove<steven.truelove@xxxxxxxxxxx>
---
fs/hugetlbfs/inode.c | 12 ++++++++----
include/linux/hugetlb.h | 3 ++-
ipc/shm.c | 2 +-
mm/mmap.c | 6 +++---
4 files changed, 14 insertions(+), 9 deletions(-)
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 1e85a7a..a97b7cc 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -928,7 +928,7 @@ static int can_do_hugetlb_shm(void)
return capable(CAP_IPC_LOCK) || in_group_p(sysctl_hugetlb_shm_group);
}
-struct file *hugetlb_file_setup(const char *name, size_t size,
+struct file *hugetlb_file_setup(const char *name, unsigned long addr, size_t size,
Just a nitpick, this line is over 80 characters.
checkpatch.pl should warn.
vm_flags_t acctflag,
struct user_struct **user, int creat_flags)
{
@@ -938,6 +938,8 @@ struct file *hugetlb_file_setup(const char *name, size_t size,
struct path path;
struct dentry *root;
struct qstr quick_string;
+ struct hstate *hstate;
+ int num_pages;
Is unsigned long better?
Thanks,
Naoya
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