[PATCH v7 13/14] xfs: prepare xfs_break_layouts() for another layout type

Dan Williams
2018-03-21T23:07:40Z

When xfs is operating as the back-end of a pNFS block server, it
prevents collisions between local and remote operations by requiring a
lease to be held for remotely accessed blocks. Local filesystem
operations break those leases before writing or mutating the extent map
of the file.

A similar mechanism is needed to prevent operations on pinned dax
mappings, like device-DMA, from colliding with extent unmap operations.

BREAK_WRITE and BREAK_UNMAPI are introduced as two distinct levels of
layout breaking.

Layouts are broken in the BREAK_WRITE case to ensure that layout-holders
do not collide with local writes. Additionally, layouts are broken in
the BREAK_UNMAPI case to make sure the layout-holder has a consistent
view of the file's extent map. While BREAK_WRITE breaks can be satisfied
be recalling FL_LAYOUT leases, BREAK_UNMAPI breaks additionally require
waiting for busy dax-pages to go idle while holding XFS_MMAPLOCK_EXCL.

After this refactoring xfs_break_layouts() becomes the entry point for
coordinating both types of breaks. Finally, xfs_break_leased_layouts()
becomes just the BREAK_WRITE handler.

Note that the unlock tracking is needed in a follow on change. That will
coordinate retrying either break handler until both successfully test
for a lease break while maintaining the lock state.

Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Reported-by: Dave Chinner <david@fromorbit.com>
Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
fs/xfs/xfs_file.c | 32 ++++++++++++++++++++++++++++++--
fs/xfs/xfs_inode.h | 16 ++++++++++++++++
fs/xfs/xfs_ioctl.c | 3 +--
fs/xfs/xfs_iops.c | 6 +++---
fs/xfs/xfs_pnfs.c | 13 +++++++------
fs/xfs/xfs_pnfs.h | 6 ++++--
6 files changed, 61 insertions(+), 15 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 18edf04811d0..7f37fadf007e 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -350,7 +350,7 @@ xfs_file_aio_write_checks(
if (error <= 0)
return error;

- error = xfs_break_layouts(inode, iolock);
+ error = xfs_break_layouts(inode, iolock, BREAK_WRITE);
if (error)
return error;

@@ -752,6 +752,34 @@ xfs_file_write_iter(
return ret;
}

+int
+xfs_break_layouts(
+ struct inode *inode,
+ uint *iolock,
+ enum layout_break_reason reason)
+{
+ struct xfs_inode *ip = XFS_I(inode);
+ bool did_unlock = false;
+ int error = 0;
+
+ ASSERT(xfs_isilocked(ip, XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL
+ | (reason == BREAK_UNMAPI
+ ? XFS_MMAPLOCK_EXCL : 0)));
+
+ switch (reason) {
+ case BREAK_UNMAPI:
+ /* fall through */
+ case BREAK_WRITE:
+ error = xfs_break_leased_layouts(inode, iolock, &did_unlock);
+ break;
+ default:
+ error = -EINVAL;
+ break;
+ }
+
+ return error;
+}
+
#define XFS_FALLOC_FL_SUPPORTED \
(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE | \
FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE | \
@@ -778,7 +806,7 @@ xfs_file_fallocate(
return -EOPNOTSUPP;

xfs_ilock(ip, iolock);
- error = xfs_break_layouts(inode, &iolock);
+ error = xfs_break_layouts(inode, &iolock, BREAK_UNMAPI);
if (error)
goto out_unlock;

diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 3e8dc990d41c..6951d57aae71 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -379,6 +379,20 @@ static inline void xfs_ifunlock(struct xfs_inode *ip)
>> XFS_ILOCK_SHIFT)

/*
+ * Layouts are broken in the BREAK_WRITE case to ensure that
+ * layout-holders do not collide with local writes. Additionally,
+ * layouts are broken in the BREAK_UNMAPI case to make sure the
+ * layout-holder has a consistent view of the file's extent map. While
+ * BREAK_WRITE breaks can be satisfied be recalling FL_LAYOUT leases,
+ * BREAK_UNMAPI breaks additionally require waiting for busy dax-pages
+ * to go idle.
+ */
+enum layout_break_reason {
+ BREAK_WRITE,
+ BREAK_UNMAPI,
+};
+
+/*
* For multiple groups support: if S_ISGID bit is set in the parent
* directory, group of new file is set to that of the parent, and
* new subdirectory gets S_ISGID bit from parent.
@@ -447,6 +461,8 @@ int xfs_zero_eof(struct xfs_inode *ip, xfs_off_t offset,
xfs_fsize_t isize, bool *did_zeroing);
int xfs_zero_range(struct xfs_inode *ip, xfs_off_t pos, xfs_off_t count,
bool *did_zero);
+int xfs_break_layouts(struct inode *inode, uint *iolock,
+ enum layout_break_reason reason);

/* from xfs_iops.c */
extern void xfs_setup_inode(struct xfs_inode *ip);
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 4151fade4bb1..967be496b052 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -39,7 +39,6 @@
#include "xfs_icache.h"
#include "xfs_symlink.h"
#include "xfs_trans.h"
-#include "xfs_pnfs.h"
#include "xfs_acl.h"
#include "xfs_btree.h"
#include <linux/fsmap.h>
@@ -644,7 +643,7 @@ xfs_ioc_space(
return error;

xfs_ilock(ip, iolock);
- error = xfs_break_layouts(inode, &iolock);
+ error = xfs_break_layouts(inode, &iolock, BREAK_UNMAPI);
if (error)
goto out_unlock;

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index d23aa08426f9..7364474347d1 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -37,7 +37,6 @@
#include "xfs_da_btree.h"
#include "xfs_dir2.h"
#include "xfs_trans_space.h"
-#include "xfs_pnfs.h"
#include "xfs_iomap.h"

#include <linux/capability.h>
@@ -1027,13 +1026,14 @@ xfs_vn_setattr(
int error;

if (iattr->ia_valid & ATTR_SIZE) {
- struct xfs_inode *ip = XFS_I(d_inode(dentry));
+ struct inode *inode = d_inode(dentry);
+ struct xfs_inode *ip = XFS_I(inode);
uint iolock;

xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
iolock = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;

- error = xfs_break_layouts(d_inode(dentry), &iolock);
+ error = xfs_break_layouts(inode, &iolock, BREAK_UNMAPI);
if (error) {
xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
return error;
diff --git a/fs/xfs/xfs_pnfs.c b/fs/xfs/xfs_pnfs.c
index 6ea7b0b55d02..40e69edb7e2e 100644
--- a/fs/xfs/xfs_pnfs.c
+++ b/fs/xfs/xfs_pnfs.c
@@ -31,17 +31,18 @@
* rules in the page fault path we don't bother.
*/
int
-xfs_break_layouts(
+xfs_break_leased_layouts(
struct inode *inode,
- uint *iolock)
+ uint *iolock,
+ bool *did_unlock)
{
struct xfs_inode *ip = XFS_I(inode);
int error;

- ASSERT(xfs_isilocked(ip, XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL));
-
+ *did_unlock = false;
while ((error = break_layout(inode, false) == -EWOULDBLOCK)) {
xfs_iunlock(ip, *iolock);
+ *did_unlock = true;
error = break_layout(inode, true);
*iolock &= ~XFS_IOLOCK_SHARED;
*iolock |= XFS_IOLOCK_EXCL;
@@ -121,8 +122,8 @@ xfs_fs_map_blocks(
* Lock out any other I/O before we flush and invalidate the pagecache,
* and then hand out a layout to the remote system. This is very
* similar to direct I/O, except that the synchronization is much more
- * complicated. See the comment near xfs_break_layouts for a detailed
- * explanation.
+ * complicated. See the comment near xfs_break_leased_layouts
+ * for a detailed explanation.
*/
xfs_ilock(ip, XFS_IOLOCK_EXCL);

diff --git a/fs/xfs/xfs_pnfs.h b/fs/xfs/xfs_pnfs.h
index bf45951e28fe..0f2f51037064 100644
--- a/fs/xfs/xfs_pnfs.h
+++ b/fs/xfs/xfs_pnfs.h
@@ -9,11 +9,13 @@ int xfs_fs_map_blocks(struct inode *inode, loff_t offset, u64 length,
int xfs_fs_commit_blocks(struct inode *inode, struct iomap *maps, int nr_maps,
struct iattr *iattr);

-int xfs_break_layouts(struct inode *inode, uint *iolock);
+int xfs_break_leased_layouts(struct inode *inode, uint *iolock,
+ bool *did_unlock);
#else
static inline int
-xfs_break_layouts(struct inode *inode, uint *iolock)
+xfs_break_leased_layouts(struct inode *inode, uint *iolock, bool *did_unlock)
{
+ *did_unlock = false;
return 0;
}
#endif /* CONFIG_EXPORTFS_BLOCK_OPS */