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Fix loop device becomes read-only 

Commit 933ec99 removes read and write from f_op because the vfs layer will
select iter_write or aio_write automatically. However, for Linux <= 4.0,
loop_set_fd will actually check f_op->write and set read-only if not exists.
This patch add them back and use the generic do_sync_{read,write} for
aio_{read,write} and new_sync_{read,write} for {read,write}_iter.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes #5776 
Closes #5855
This commit is contained in:
Chunwei Chen 2017-03-06 09:20:20 -08:00 committed by Brian Behlendorf
parent fb963d33ee
commit 7a789346af
2 changed files with 27 additions and 1 deletions
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22
config/kernel-vfs-rw-iterate.m4
View File

@ -1,5 +1,5 @@
dnl #
dnl # Linux 4.1.x API
dnl # Linux 3.16 API
dnl #
AC_DEFUN([ZFS_AC_KERNEL_VFS_RW_ITERATE],
[AC_MSG_CHECKING([whether fops->read/write_iter() are available])
@ -21,6 +21,26 @@ AC_DEFUN([ZFS_AC_KERNEL_VFS_RW_ITERATE],
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_VFS_RW_ITERATE, 1,
[fops->read/write_iter() are available])
ZFS_AC_KERNEL_NEW_SYNC_READ
],[
AC_MSG_RESULT(no)
])
])
dnl #
dnl # Linux 4.1 API
dnl #
AC_DEFUN([ZFS_AC_KERNEL_NEW_SYNC_READ],
[AC_MSG_CHECKING([whether new_sync_read() is available])
ZFS_LINUX_TRY_COMPILE([
#include <linux/fs.h>
],[
new_sync_read(NULL, NULL, 0, NULL);
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_NEW_SYNC_READ, 1,
[new_sync_read() is available])
],[
AC_MSG_RESULT(no)
])

6
module/zfs/zpl_file.c
View File

@ -856,9 +856,15 @@ const struct file_operations zpl_file_operations = {
.release = zpl_release,
.llseek = zpl_llseek,
#ifdef HAVE_VFS_RW_ITERATE
#ifdef HAVE_NEW_SYNC_READ
.read = new_sync_read,
.write = new_sync_write,
#endif
.read_iter = zpl_iter_read,
.write_iter = zpl_iter_write,
#else
.read = do_sync_read,
.write = do_sync_write,
.aio_read = zpl_aio_read,
.aio_write = zpl_aio_write,
#endif