From 1bf649cb0a1cc6e48dce848611ba327eb283000e Mon Sep 17 00:00:00 2001 From: Rob Norris Date: Wed, 10 Apr 2024 13:14:13 +1000 Subject: [PATCH] vdev_disk: fix alignment check when buffer has non-zero starting offset If a linear buffer spans multiple pages, and the first page has a non-zero starting offset, the checker would not include the offset, and so would think there was an alignment gap at the end of the first page, rather than at the start. That is, for a 16K buffer spread across five pages with an initial 512B offset: [.XXXXXXX][XXXXXXXX][XXXXXXXX][XXXXXXXX][XXXXXXX.] It would be interpreted as: [XXXXXXX.][XXXXXXXX]... And be rejected as misaligned. Since it's already a linear ABD, the "linearising" copy would just reuse the buffer as-is, and the second check would failing, tripping the VERIFY in vdev_disk_io_rw(). This commit fixes all this by including the offset in the check for end-of-page alignment. Sponsored-by: Klara, Inc. Sponsored-by: Wasabi Technology, Inc. Reviewed-by: Alexander Motin Reviewed-by: Brian Behlendorf Signed-off-by: Rob Norris Closes #16076 --- module/os/linux/zfs/vdev_disk.c | 2 +- tests/zfs-tests/tests/functional/vdev_disk/page_alignment.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/module/os/linux/zfs/vdev_disk.c b/module/os/linux/zfs/vdev_disk.c index 77773c4f2..f3f0c0875 100644 --- a/module/os/linux/zfs/vdev_disk.c +++ b/module/os/linux/zfs/vdev_disk.c @@ -882,7 +882,7 @@ vdev_disk_check_pages_cb(struct page *page, size_t off, size_t len, void *priv) * Note if we're taking less than a full block, so we can check it * above on the next call. */ - s->end = len & s->bmask; + s->end = (off+len) & s->bmask; /* All blocks after the first must start on a block size boundary. */ if (s->npages != 0 && (off & s->bmask) != 0) diff --git a/tests/zfs-tests/tests/functional/vdev_disk/page_alignment.c b/tests/zfs-tests/tests/functional/vdev_disk/page_alignment.c index 98d19a128..5c6d28eb2 100644 --- a/tests/zfs-tests/tests/functional/vdev_disk/page_alignment.c +++ b/tests/zfs-tests/tests/functional/vdev_disk/page_alignment.c @@ -61,7 +61,7 @@ vdev_disk_check_pages_cb(struct page *page, size_t off, size_t len, void *priv) * Note if we're taking less than a full block, so we can check it * above on the next call. */ - s->end = len & s->bmask; + s->end = (off+len) & s->bmask; /* All blocks after the first must start on a block size boundary. */ if (s->npages != 0 && (off & s->bmask) != 0)