[patch] factor out checks against the memlock rlimit
From: Jeff Moyer
Date: Mon Mar 09 2009 - 11:55:31 EST
Hi,
There are several places in the kernel where the memlock rlimit is
checked, all duplicating code. I added another in a recent patch and it
made me feel dirty, so this patch factors all of that into a single
function, can_mlock_pages.
The infiniband implementation of the rlimit check was actually broken.
Weeding through changelogs showed that the initial implementation was
wrong, code was #if 0'd out because it didn't work, and instead of
fixing things, they just removed the code all together. If my
assessment of that is wrong, please let me know! ;-)
Comments, as always, are encouraged.
Cheers,
Jeff
diff --git a/drivers/infiniband/core/umem.c b/drivers/infiniband/core/umem.c
index 6f7c096..c4d4f1b 100644
--- a/drivers/infiniband/core/umem.c
+++ b/drivers/infiniband/core/umem.c
@@ -135,14 +135,11 @@ struct ib_umem *ib_umem_get(struct ib_ucontext *context, unsigned long addr,
down_write(¤t->mm->mmap_sem);
- locked = npages + current->mm->locked_vm;
- lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
-
- if ((locked > lock_limit) && !capable(CAP_IPC_LOCK)) {
+ if (!can_mlock_pages(npages)) {
ret = -ENOMEM;
goto out;
}
-
+ locked = npages + current->mm->locked_vm;
cur_base = addr & PAGE_MASK;
ret = 0;
diff --git a/drivers/infiniband/hw/ipath/ipath_user_pages.c b/drivers/infiniband/hw/ipath/ipath_user_pages.c
index 0190edc..9ab17e3 100644
--- a/drivers/infiniband/hw/ipath/ipath_user_pages.c
+++ b/drivers/infiniband/hw/ipath/ipath_user_pages.c
@@ -58,10 +58,7 @@ static int __get_user_pages(unsigned long start_page, size_t num_pages,
size_t got;
int ret;
- lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur >>
- PAGE_SHIFT;
-
- if (num_pages > lock_limit) {
+ if (!can_mlock_pages(num_pages)) {
ret = -ENOMEM;
goto bail;
}
diff --git a/fs/aio.c b/fs/aio.c
index 3bbda9d..0ca64eb 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -136,10 +136,7 @@ static int aio_setup_ring(struct kioctx *ctx)
* Check that the memory reserved for the completion ring does
* not exceed the memlock memory limit.
*/
- locked = nr_pages + ctx->mm->locked_vm;
- lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
- lock_limit >>= PAGE_SHIFT;
- if ((locked > lock_limit) && !capable(CAP_IPC_LOCK)) {
+ if (!can_mlock_pages(nr_pages)) {
up_write(&ctx->mm->mmap_sem);
info->mmap_size = 0;
aio_free_ring(ctx);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 065cdf8..79c1127 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -737,6 +737,7 @@ extern unsigned long shmem_get_unmapped_area(struct file *file,
#endif
extern int can_do_mlock(void);
+extern int can_mlock_pages(unsigned long);
extern int user_shm_lock(size_t, struct user_struct *);
extern void user_shm_unlock(size_t, struct user_struct *);
diff --git a/mm/mlock.c b/mm/mlock.c
index cbe9e05..4ec96c2 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -31,6 +31,33 @@ int can_do_mlock(void)
}
EXPORT_SYMBOL(can_do_mlock);
+/**
+ * can_mlock_pages() - tell whether mlocking nr_pages is possible
+ * @nr_pages: Number of pages to be locked in memory
+ *
+ * Boolean function which tells whether the MEMLOCK rlimit will prevent
+ * locking nr_pages pages.
+ */
+int can_mlock_pages(unsigned long nr_pages)
+{
+ unsigned long locked, lock_limit;
+
+ if (capable(CAP_IPC_LOCK))
+ return 1;
+
+ locked = nr_pages;
+ locked += current->mm->locked_vm;
+
+ lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
+ lock_limit >>= PAGE_SHIFT;
+
+ /* check against resource limits */
+ if (locked <= lock_limit)
+ return 1;
+ return 0;
+}
+EXPORT_SYMBOL(can_mlock_pages);
+
#ifdef CONFIG_UNEVICTABLE_LRU
/*
* Mlocked pages are marked with PageMlocked() flag for efficient testing
@@ -505,14 +532,8 @@ SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
start &= PAGE_MASK;
- locked = len >> PAGE_SHIFT;
- locked += current->mm->locked_vm;
-
- lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
- lock_limit >>= PAGE_SHIFT;
-
/* check against resource limits */
- if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
+ if (can_mlock_pages(len >> PAGE_SHIFT))
error = do_mlock(start, len, 1);
up_write(¤t->mm->mmap_sem);
return error;
diff --git a/mm/mmap.c b/mm/mmap.c
index 00ced3e..52d1c32 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -975,12 +975,7 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
/* mlock MCL_FUTURE? */
if (vm_flags & VM_LOCKED) {
- unsigned long locked, lock_limit;
- locked = len >> PAGE_SHIFT;
- locked += mm->locked_vm;
- lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
- lock_limit >>= PAGE_SHIFT;
- if (locked > lock_limit && !capable(CAP_IPC_LOCK))
+ if (!can_mlock_pages(len >> PAGE_SHIFT))
return -EAGAIN;
}
@@ -2006,12 +2001,7 @@ unsigned long do_brk(unsigned long addr, unsigned long len)
* mlock MCL_FUTURE?
*/
if (mm->def_flags & VM_LOCKED) {
- unsigned long locked, lock_limit;
- locked = len >> PAGE_SHIFT;
- locked += mm->locked_vm;
- lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
- lock_limit >>= PAGE_SHIFT;
- if (locked > lock_limit && !capable(CAP_IPC_LOCK))
+ if (!can_mlock_pages(len>>PAGE_SHIFT))
return -EAGAIN;
}
diff --git a/mm/mremap.c b/mm/mremap.c
index a39b7b9..6fb50e2 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -342,12 +342,8 @@ unsigned long do_mremap(unsigned long addr,
goto out;
}
if (vma->vm_flags & VM_LOCKED) {
- unsigned long locked, lock_limit;
- locked = mm->locked_vm << PAGE_SHIFT;
- lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
- locked += new_len - old_len;
ret = -EAGAIN;
- if (locked > lock_limit && !capable(CAP_IPC_LOCK))
+ if (!can_mlock_pages((new_len - old_len)>>PAGE_SHIFT))
goto out;
}
if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
--
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