From 2581d12ef0222467b32a13e61a983981846afd3c Mon Sep 17 00:00:00 2001 From: Asahi Lina Date: Fri, 1 Nov 2024 20:57:43 +0900 Subject: [PATCH] patches: Add two patches with DAX fixes Signed-off-by: Asahi Lina --- .../0019-dax-Allow-block-size-PAGE_SIZE.patch | 39 +++++++++ ..._copy_user-fallback-path-for-remote-.patch | 86 +++++++++++++++++++ 2 files changed, 125 insertions(+) create mode 100644 patches/0019-dax-Allow-block-size-PAGE_SIZE.patch create mode 100644 patches/0020-mm-Fix-__wp_page_copy_user-fallback-path-for-remote-.patch diff --git a/patches/0019-dax-Allow-block-size-PAGE_SIZE.patch b/patches/0019-dax-Allow-block-size-PAGE_SIZE.patch new file mode 100644 index 0000000..f2a6d9d --- /dev/null +++ b/patches/0019-dax-Allow-block-size-PAGE_SIZE.patch @@ -0,0 +1,39 @@ +From ce899b86d685b28016cc27c505d1fdca468c9b2e Mon Sep 17 00:00:00 2001 +From: Asahi Lina +Date: Sun, 20 Oct 2024 01:23:41 +0900 +Subject: [PATCH 1/2] dax: Allow block size > PAGE_SIZE + +For virtio-dax, the file/FS blocksize is irrelevant. FUSE always uses +large DAX blocks (2MiB), which will work with all host page sizes. Since +we are mapping files into the DAX window on the host, the underlying +block size of the filesystem and its block device (if any) are +meaningless. + +For real devices with DAX, the only requirement should be that the FS +block size is *at least* as large as PAGE_SIZE, to ensure that at least +whole pages can be mapped out of the device contiguously. + +Fixes warning when using virtio-dax on a 4K guest with a 16K host, +backed by tmpfs (which sets blksz == PAGE_SIZE on the host). + +Signed-off-by: Asahi Lina +--- + fs/dax.c | 2 +- + 1 file changed, 1 insertion(+), 1 deletion(-) + +diff --git a/fs/dax.c b/fs/dax.c +index becb4a6920c6..2ef3b50e8d7a 100644 +--- a/fs/dax.c ++++ b/fs/dax.c +@@ -1032,7 +1032,7 @@ int dax_writeback_mapping_range(struct address_space *mapping, + int ret = 0; + unsigned int scanned = 0; + +- if (WARN_ON_ONCE(inode->i_blkbits != PAGE_SHIFT)) ++ if (WARN_ON_ONCE(inode->i_blkbits < PAGE_SHIFT)) + return -EIO; + + if (mapping_empty(mapping) || wbc->sync_mode != WB_SYNC_ALL) +-- +2.47.0 + diff --git a/patches/0020-mm-Fix-__wp_page_copy_user-fallback-path-for-remote-.patch b/patches/0020-mm-Fix-__wp_page_copy_user-fallback-path-for-remote-.patch new file mode 100644 index 0000000..5d361ff --- /dev/null +++ b/patches/0020-mm-Fix-__wp_page_copy_user-fallback-path-for-remote-.patch @@ -0,0 +1,86 @@ +From 9b1ab7cc1eb019d9e8ce1b63954c58eb0fbecd2c Mon Sep 17 00:00:00 2001 +From: Asahi Lina +Date: Mon, 21 Oct 2024 23:21:16 +0900 +Subject: [PATCH 2/2] mm: Fix __wp_page_copy_user fallback path for remote mm + +If the source page is a PFN mapping, we copy back from userspace. +However, if this fault is a remote access, we cannot use +__copy_from_user_inatomic. Instead, use access_remote_vm() in this case. + +Fixes WARN when writing to CoW mappings into a remote process, such as +when using gdb on a binary present on a DAX filesystem. + +[ 143.683782] ------------[ cut here ]------------ +[ 143.683784] WARNING: CPU: 1 PID: 350 at mm/memory.c:2904 __wp_page_copy_user+0x120/0x2bc +[ 143.683793] CPU: 1 PID: 350 Comm: gdb Not tainted 6.6.52 #1 +[ 143.683794] Hardware name: linux,dummy-virt (DT) +[ 143.683795] pstate: 61400005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) +[ 143.683796] pc : __wp_page_copy_user+0x120/0x2bc +[ 143.683798] lr : __wp_page_copy_user+0x254/0x2bc +[ 143.683799] sp : ffff80008272b8b0 +[ 143.683799] x29: ffff80008272b8b0 x28: 0000000000000000 x27: ffff000083bad580 +[ 143.683801] x26: 0000000000000000 x25: 0000fffff7fd5000 x24: ffff000081db04c0 +[ 143.683802] x23: ffff00014f24b000 x22: fffffc00053c92c0 x21: ffff000083502150 +[ 143.683803] x20: 0000fffff7fd5000 x19: ffff80008272b9d0 x18: 0000000000000000 +[ 143.683804] x17: ffff000081db0500 x16: ffff800080fe52a0 x15: 0000fffff7fd5000 +[ 143.683804] x14: 0000000000bb1845 x13: 0000000000000080 x12: ffff80008272b880 +[ 143.683805] x11: ffff000081d13600 x10: ffff000081d13608 x9 : ffff000081d1360c +[ 143.683806] x8 : ffff000083a16f00 x7 : 0000000000000010 x6 : ffff00014f24b000 +[ 143.683807] x5 : ffff00014f24c000 x4 : 0000000000000000 x3 : ffff000083582000 +[ 143.683807] x2 : 0000000000000f80 x1 : 0000fffff7fd5000 x0 : 0000000000001000 +[ 143.683808] Call trace: +[ 143.683809] __wp_page_copy_user+0x120/0x2bc +[ 143.683810] wp_page_copy+0x98/0x5c0 +[ 143.683813] do_wp_page+0x250/0x530 +[ 143.683814] __handle_mm_fault+0x278/0x284 +[ 143.683817] handle_mm_fault+0x64/0x1e8 +[ 143.683819] faultin_page+0x5c/0x110 +[ 143.683820] __get_user_pages+0xc8/0x2f4 +[ 143.683821] get_user_pages_remote+0xac/0x30c +[ 143.683823] __access_remote_vm+0xb4/0x368 +[ 143.683824] access_remote_vm+0x10/0x1c +[ 143.683826] mem_rw.isra.0+0xc4/0x218 +[ 143.683831] mem_write+0x18/0x24 +[ 143.683831] vfs_write+0xa0/0x37c +[ 143.683834] ksys_pwrite64+0x7c/0xc0 +[ 143.683834] __arm64_sys_pwrite64+0x20/0x2c +[ 143.683835] invoke_syscall+0x48/0x10c +[ 143.683837] el0_svc_common.constprop.0+0x40/0xe0 +[ 143.683839] do_el0_svc+0x1c/0x28 +[ 143.683841] el0_svc+0x3c/0xdc +[ 143.683846] el0t_64_sync_handler+0x120/0x12c +[ 143.683848] el0t_64_sync+0x194/0x198 +[ 143.683849] ---[ end trace 0000000000000000 ]--- + +Signed-off-by: Asahi Lina +--- + mm/memory.c | 7 ++++++- + 1 file changed, 6 insertions(+), 1 deletion(-) + +diff --git a/mm/memory.c b/mm/memory.c +index ebfc9768f801..277079edd24b 100644 +--- a/mm/memory.c ++++ b/mm/memory.c +@@ -3078,13 +3078,18 @@ static inline int __wp_page_copy_user(struct page *dst, struct page *src, + update_mmu_cache_range(vmf, vma, addr, vmf->pte, 1); + } + ++ /* If the mm is a remote mm, copy in the page using access_remote_vm() */ ++ if (current->mm != mm) { ++ if (access_remote_vm(mm, (unsigned long)uaddr, kaddr, PAGE_SIZE, 0) != PAGE_SIZE) ++ goto warn; ++ } + /* + * This really shouldn't fail, because the page is there + * in the page tables. But it might just be unreadable, + * in which case we just give up and fill the result with + * zeroes. + */ +- if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) { ++ else if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) { + if (vmf->pte) + goto warn; + +-- +2.47.0 +