Messages in this thread | | | Date | Wed, 07 Mar 2012 18:29:51 -0500 | From | Steven Truelove <> | Subject | Re: [PATCH] Correct alignment of huge page requests. |
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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@utoronto.ca> >> --- >> 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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