On 2023-07-19 17:20, Helge Deller wrote:
The io_uring testcase is broken on IA-64 since commit d808459b2e31
("io_uring: Adjust mapping wrt architecture aliasing requirements").
The reason is, that this commit introduced an own architecture
independend get_unmapped_area() search algorithm which doesn't suite
the
memory region requirements for IA-64.
To avoid similar problems in the future it's better to switch back to
the architecture-provided get_unmapped_area() function and adjust the
needed input parameters before the call. Additionally
io_uring_mmu_get_unmapped_area() will now become easier to understand
and maintain.
This patch has been tested on physical IA-64 and PA-RISC machines,
without any failures in the io_uring testcases. On PA-RISC the
LTP mmmap testcases did not report any regressions either.
I don't expect issues for other architectures, but it would be nice if
this patch could be tested on other machines too.
Reported-by: matoro <matoro_mailinglist_kernel@xxxxxxxxx>
Fixes: d808459b2e31 ("io_uring: Adjust mapping wrt architecture
aliasing requirements")
Signed-off-by: Helge Deller <deller@xxxxxx>
diff --git a/arch/ia64/kernel/sys_ia64.c b/arch/ia64/kernel/sys_ia64.c
index 6e948d015332..eb561cc93632 100644
--- a/arch/ia64/kernel/sys_ia64.c
+++ b/arch/ia64/kernel/sys_ia64.c
@@ -63,7 +63,7 @@ arch_get_unmapped_area (struct file *filp, unsigned
long addr, unsigned long len
info.low_limit = addr;
info.high_limit = TASK_SIZE;
info.align_mask = align_mask;
- info.align_offset = 0;
+ info.align_offset = pgoff << PAGE_SHIFT;
return vm_unmapped_area(&info);
}
diff --git a/arch/parisc/kernel/sys_parisc.c
b/arch/parisc/kernel/sys_parisc.c
index 39acccabf2ed..465b7cb9d44f 100644
--- a/arch/parisc/kernel/sys_parisc.c
+++ b/arch/parisc/kernel/sys_parisc.c
@@ -26,12 +26,17 @@
#include <linux/compat.h>
/*
- * Construct an artificial page offset for the mapping based on the
physical
+ * Construct an artificial page offset for the mapping based on the
virtual
* address of the kernel file mapping variable.
+ * If filp is zero the calculated pgoff value aliases the memory of
the given
+ * address. This is useful for io_uring where the mapping shall alias
a kernel
+ * address and a userspace adress where both the kernel and the
userspace
+ * access the same memory region.
*/
-#define GET_FILP_PGOFF(filp) \
- (filp ? (((unsigned long) filp->f_mapping) >> 8) \
- & ((SHM_COLOUR-1) >> PAGE_SHIFT) : 0UL)
+#define GET_FILP_PGOFF(filp, addr) \
+ ((filp ? (((unsigned long) filp->f_mapping) >> 8) \
+ & ((SHM_COLOUR-1) >> PAGE_SHIFT) : 0UL) \
+ + (addr >> PAGE_SHIFT))
static unsigned long shared_align_offset(unsigned long filp_pgoff,
unsigned long pgoff)
@@ -111,7 +116,7 @@ static unsigned long
arch_get_unmapped_area_common(struct file *filp,
do_color_align = 0;
if (filp || (flags & MAP_SHARED))
do_color_align = 1;
- filp_pgoff = GET_FILP_PGOFF(filp);
+ filp_pgoff = GET_FILP_PGOFF(filp, addr);
if (flags & MAP_FIXED) {
/* Even MAP_FIXED mappings must reside within TASK_SIZE */
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index f1b79959d1c1..70eb01faf15f 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -3425,8 +3425,6 @@ static unsigned long
io_uring_mmu_get_unmapped_area(struct file *filp,
unsigned long addr, unsigned long len,
unsigned long pgoff, unsigned long flags)
{
- const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags);
- struct vm_unmapped_area_info info;
void *ptr;
/*
@@ -3441,32 +3439,26 @@ static unsigned long
io_uring_mmu_get_unmapped_area(struct file *filp,
if (IS_ERR(ptr))
return -ENOMEM;
- info.flags = VM_UNMAPPED_AREA_TOPDOWN;
- info.length = len;
- info.low_limit = max(PAGE_SIZE, mmap_min_addr);
- info.high_limit = arch_get_mmap_base(addr, current->mm->mmap_base);
+ /*
+ * Some architectures have strong cache aliasing requirements.
+ * For such architectures we need a coherent mapping which aliases
+ * kernel memory *and* userspace memory. To achieve that:
+ * - use a NULL file pointer to reference physical memory, and
+ * - use the kernel virtual address of the shared io_uring context
+ * (instead of the userspace-provided address, which has to be 0UL
+ * anyway).
+ * For architectures without such aliasing requirements, the
+ * architecture will return any suitable mapping because addr is 0.
+ */
+ filp = NULL;
+ flags |= MAP_SHARED;
+ pgoff = 0; /* has been translated to ptr above */
#ifdef SHM_COLOUR
- info.align_mask = PAGE_MASK & (SHM_COLOUR - 1UL);
+ addr = (uintptr_t) ptr;
#else
- info.align_mask = PAGE_MASK & (SHMLBA - 1UL);
+ addr = 0UL;
#endif
- info.align_offset = (unsigned long) ptr;
-
- /*
- * A failed mmap() very likely causes application failure,
- * so fall back to the bottom-up function here. This scenario
- * can happen with large stack limits and large mmap()
- * allocations.
- */
- addr = vm_unmapped_area(&info);
- if (offset_in_page(addr)) {
- info.flags = 0;
- info.low_limit = TASK_UNMAPPED_BASE;
- info.high_limit = mmap_end;
- addr = vm_unmapped_area(&info);
- }
-
- return addr;
+ return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
}
#else /* !CONFIG_MMU */
Tested-by: matoro <matoro_mailinglist_kernel@xxxxxxxxx>
On 6.4.4. The NFS thing I mentioned in our previous emails appears to
be a separate regression not related to io_uring.
