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Update pin_user_pages() calls for Direct I/O

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Originally #16856 updated Linux Direct I/O requests to use the new
pin_user_pages API. However, it was an oversight that this PR only
handled iov_iter's of type ITER_IOVEC and ITER_UBUF. Other iov_iter
types may try and use the pin_user_pages API if it is available. This
can lead to panics as the iov_iter is not being iterated over correctly
in zfs_uio_pin_user_pages().

Unfortunately, generic iov_iter API's that call pin_user_page_fast() are
protected as GPL only. Rather than update zfs_uio_pin_user_pages() to
account for all iov_iter types, we can simply just call
zfs_uio_get_dio_page_iov_iter() if the iov_iter type is not ITER_IOVEC
or ITER_UBUF. zfs_uio_get_dio_page_iov_iter() calls the
iov_iter_get_pages() calls that can handle any iov_iter type.

In the future it might be worth using the exposed iov_iter iterator
functions that are included in the header iov_iter.h since v6.7. These
functions allow for any iov_iter type to be iterated over and advanced
while applying a step function during iteration. This could possibly be
leveraged in zfs_uio_pin_user_pages().

A new ZFS test case was added to test that a ITER_BVEC is handled
correctly using this new code path. This test case was provided though
issue #16956.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ameer Hamza <ahamza@ixsystems.com>
Signed-off-by: Brian Atkinson <batkinson@lanl.gov>
Closes #16956 
Closes #17006
This commit is contained in:
Brian Atkinson
2025-01-30 18:53:59 -05:00
committed by GitHub
parent 12f0baf348
commit 1e32c57893
6 changed files with 159 additions and 27 deletions
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config/kernel-vfs-iov_iter.m4
+27
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@@ -21,6 +21,20 @@ AC_DEFUN([ZFS_AC_KERNEL_SRC_VFS_IOV_ITER], [
__attribute__((unused)) enum iter_type i = iov_iter_type(&iter);
])
ZFS_LINUX_TEST_SRC([iov_iter_get_pages2], [
#include <linux/uio.h>
],[
struct iov_iter iter = { 0 };
struct page **pages = NULL;
size_t maxsize = 4096;
unsigned maxpages = 1;
size_t start;
size_t ret __attribute__ ((unused));
ret = iov_iter_get_pages2(&iter, pages, maxsize, maxpages,
&start);
])
ZFS_LINUX_TEST_SRC([iter_is_ubuf], [
#include <linux/uio.h>
],[
@@ -64,6 +78,19 @@ AC_DEFUN([ZFS_AC_KERNEL_VFS_IOV_ITER], [
AC_MSG_RESULT(no)
])
dnl #
dnl # Kernel 6.0 changed iov_iter_get_pages() to iov_iter_get_pages2().
dnl #
AC_MSG_CHECKING([whether iov_iter_get_pages2() is available])
ZFS_LINUX_TEST_RESULT([iov_iter_get_pages2], [
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_IOV_ITER_GET_PAGES2, 1,
[iov_iter_get_pages2() is available])
],[
AC_MSG_RESULT(no)
])
dnl #
dnl # Kernel 6.0 introduced the ITER_UBUF iov_iter type. iter_is_ubuf()
dnl # was also added to determine if the iov_iter is an ITER_UBUF.