MAP_DIRECT is an mmap(2) flag with the following semantics:
MAP_DIRECT
When specified with MAP_SHARED_VALIDATE, sets up a file lease with the
same lifetime as the mapping. Unlike a typical F_RDLCK lease this lease
is broken when a "lease breaker" attempts to write(2), change the block
map (fallocate), or change the size of the file. Otherwise the mechanism
of a lease break is identical to the typical lease break case where the
lease needs to be removed (munmap) within the number of seconds
specified by /proc/sys/fs/lease-break-time. If the lease holder fails to
remove the lease in time the kernel will invalidate the mapping and
force all future accesses to the mapping to trigger SIGBUS.
In addition to lease break timeouts causing faults in the mapping to
result in SIGBUS, other states of the file will trigger SIGBUS at fault
time:
* The file is not DAX capable
* The file has reflinked (copy-on-write) blocks
* The fault would trigger the filesystem to allocate blocks
* The fault would trigger the filesystem to perform extent conversion
In other words, MAP_DIRECT expects and enforces a fully allocated file
where faults can be satisfied without modifying block map metadata.
An unprivileged process may establish a MAP_DIRECT mapping on a file
whose UID (owner) matches the filesystem UID of the process. A process
with the CAP_LEASE capability may establish a MAP_DIRECT mapping on
arbitrary files
ERRORS
EACCES Beyond the typical mmap(2) conditions that trigger EACCES
MAP_DIRECT also requires the permission to set a file lease.
EOPNOTSUPP The filesystem explicitly does not support the flag
SIGBUS Attempted to write a MAP_DIRECT mapping at a file offset that
might require block-map updates, or the lease timed out and the
kernel invalidated the mapping.
Cc: Jan Kara <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Jeff Moyer <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: "Darrick J. Wong" <[email protected]>
Cc: Ross Zwisler <[email protected]>
Cc: Jeff Layton <[email protected]>
Cc: "J. Bruce Fields" <[email protected]>
Signed-off-by: Dan Williams <[email protected]>
---
fs/xfs/Kconfig | 2 -
fs/xfs/xfs_file.c | 102 +++++++++++++++++++++++++++++++++++++++
include/linux/mman.h | 3 +
include/uapi/asm-generic/mman.h | 1
4 files changed, 106 insertions(+), 2 deletions(-)
diff --git a/fs/xfs/Kconfig b/fs/xfs/Kconfig
index f62fc6629abb..f8765653a438 100644
--- a/fs/xfs/Kconfig
+++ b/fs/xfs/Kconfig
@@ -112,4 +112,4 @@ config XFS_ASSERT_FATAL
config XFS_LAYOUT
def_bool y
- depends on EXPORTFS_BLOCK_OPS
+ depends on EXPORTFS_BLOCK_OPS || FS_DAX
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index ebdd0bd2b261..e35518600e28 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -40,12 +40,22 @@
#include "xfs_iomap.h"
#include "xfs_reflink.h"
+#include <linux/mman.h>
#include <linux/dcache.h>
#include <linux/falloc.h>
#include <linux/pagevec.h>
+#include <linux/mapdirect.h>
#include <linux/backing-dev.h>
static const struct vm_operations_struct xfs_file_vm_ops;
+static const struct vm_operations_struct xfs_file_vm_direct_ops;
+
+static inline bool
+is_xfs_map_direct(
+ struct vm_area_struct *vma)
+{
+ return vma->vm_ops == &xfs_file_vm_direct_ops;
+}
/*
* Clear the specified ranges to zero through either the pagecache or DAX.
@@ -1008,6 +1018,26 @@ xfs_file_llseek(
return vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
}
+static int
+xfs_vma_checks(
+ struct vm_area_struct *vma,
+ struct inode *inode)
+{
+ if (!is_xfs_map_direct(vma))
+ return 0;
+
+ if (!is_map_direct_valid(vma->vm_private_data))
+ return VM_FAULT_SIGBUS;
+
+ if (xfs_is_reflink_inode(XFS_I(inode)))
+ return VM_FAULT_SIGBUS;
+
+ if (!IS_DAX(inode))
+ return VM_FAULT_SIGBUS;
+
+ return 0;
+}
+
/*
* Locking for serialisation of IO during page faults. This results in a lock
* ordering of:
@@ -1024,6 +1054,7 @@ __xfs_filemap_fault(
enum page_entry_size pe_size,
bool write_fault)
{
+ struct vm_area_struct *vma = vmf->vma;
struct inode *inode = file_inode(vmf->vma->vm_file);
struct xfs_inode *ip = XFS_I(inode);
int ret;
@@ -1032,10 +1063,14 @@ __xfs_filemap_fault(
if (write_fault) {
sb_start_pagefault(inode->i_sb);
- file_update_time(vmf->vma->vm_file);
+ file_update_time(vma->vm_file);
}
xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
+ ret = xfs_vma_checks(vma, inode);
+ if (ret)
+ goto out_unlock;
+
if (IS_DAX(inode)) {
ret = dax_iomap_fault(vmf, pe_size, &xfs_iomap_ops);
} else {
@@ -1044,6 +1079,8 @@ __xfs_filemap_fault(
else
ret = filemap_fault(vmf);
}
+
+out_unlock:
xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
if (write_fault)
@@ -1115,6 +1152,31 @@ xfs_filemap_pfn_mkwrite(
}
+static void
+xfs_filemap_direct_open(
+ struct vm_area_struct *vma)
+{
+ get_map_direct_vma(vma->vm_private_data);
+}
+
+static void
+xfs_filemap_direct_close(
+ struct vm_area_struct *vma)
+{
+ put_map_direct_vma(vma->vm_private_data);
+}
+
+static const struct vm_operations_struct xfs_file_vm_direct_ops = {
+ .fault = xfs_filemap_fault,
+ .huge_fault = xfs_filemap_huge_fault,
+ .map_pages = filemap_map_pages,
+ .page_mkwrite = xfs_filemap_page_mkwrite,
+ .pfn_mkwrite = xfs_filemap_pfn_mkwrite,
+
+ .open = xfs_filemap_direct_open,
+ .close = xfs_filemap_direct_close,
+};
+
static const struct vm_operations_struct xfs_file_vm_ops = {
.fault = xfs_filemap_fault,
.huge_fault = xfs_filemap_huge_fault,
@@ -1135,6 +1197,43 @@ xfs_file_mmap(
return 0;
}
+#define XFS_MAP_SUPPORTED (LEGACY_MAP_MASK | MAP_DIRECT)
+
+STATIC int
+xfs_file_mmap_validate(
+ struct file *filp,
+ struct vm_area_struct *vma,
+ unsigned long map_flags,
+ int fd)
+{
+ struct inode *inode = file_inode(filp);
+ struct xfs_inode *ip = XFS_I(inode);
+ struct map_direct_state *mds;
+
+ if (map_flags & ~(XFS_MAP_SUPPORTED))
+ return -EOPNOTSUPP;
+
+ if ((map_flags & MAP_DIRECT) == 0)
+ return xfs_file_mmap(filp, vma);
+
+ file_accessed(filp);
+ vma->vm_ops = &xfs_file_vm_direct_ops;
+ if (IS_DAX(inode))
+ vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
+
+ mds = map_direct_register(fd, vma);
+ if (IS_ERR(mds))
+ return PTR_ERR(mds);
+
+ /* flush in-flight faults */
+ xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
+ xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
+
+ vma->vm_private_data = mds;
+
+ return 0;
+}
+
const struct file_operations xfs_file_operations = {
.llseek = xfs_file_llseek,
.read_iter = xfs_file_read_iter,
@@ -1146,6 +1245,7 @@ const struct file_operations xfs_file_operations = {
.compat_ioctl = xfs_file_compat_ioctl,
#endif
.mmap = xfs_file_mmap,
+ .mmap_validate = xfs_file_mmap_validate,
.open = xfs_file_open,
.release = xfs_file_release,
.fsync = xfs_file_fsync,
diff --git a/include/linux/mman.h b/include/linux/mman.h
index 94b63b4d71ff..fab393a9dda9 100644
--- a/include/linux/mman.h
+++ b/include/linux/mman.h
@@ -20,6 +20,9 @@
#ifndef MAP_HUGE_1GB
#define MAP_HUGE_1GB 0
#endif
+#ifndef MAP_DIRECT
+#define MAP_DIRECT 0
+#endif
#ifndef MAP_UNINITIALIZED
#define MAP_UNINITIALIZED 0
#endif
diff --git a/include/uapi/asm-generic/mman.h b/include/uapi/asm-generic/mman.h
index 7162cd4cca73..c916f22008e0 100644
--- a/include/uapi/asm-generic/mman.h
+++ b/include/uapi/asm-generic/mman.h
@@ -12,6 +12,7 @@
#define MAP_NONBLOCK 0x10000 /* do not block on IO */
#define MAP_STACK 0x20000 /* give out an address that is best
suited for process/thread stacks */
#define MAP_HUGETLB 0x40000 /* create a huge page mapping */
+#define MAP_DIRECT 0x80000 /* leased block map (layout) for DAX */
/* Bits [26:31] are reserved, see mman-common.h for MAP_HUGETLB usage */
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