xfs: prepare xfs_break_layouts() for another layout type

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_UNMAP 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_UNMAP 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_UNMAP 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: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Reported-by: Dave Chinner <david@fromorbit.com>
Reported-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Dan Williams 2018-03-20 14:42:38 -07:00
parent c63a8eae63
commit 69eb5fa10e
6 changed files with 53 additions and 15 deletions

View File

@ -312,7 +312,7 @@ 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;
@ -718,6 +718,28 @@ xfs_file_write_iter(
return ret;
}
int
xfs_break_layouts(
struct inode *inode,
uint *iolock,
enum layout_break_reason reason)
{
bool retry;
ASSERT(xfs_isilocked(XFS_I(inode), XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL));
switch (reason) {
case BREAK_UNMAP:
ASSERT(xfs_isilocked(XFS_I(inode), XFS_MMAPLOCK_EXCL));
/* fall through */
case BREAK_WRITE:
return xfs_break_leased_layouts(inode, iolock, &retry);
default:
WARN_ON_ONCE(1);
return -EINVAL;
}
}
#define XFS_FALLOC_FL_SUPPORTED \
(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE | \
FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE | \
@ -744,7 +766,7 @@ xfs_file_fallocate(
return -EOPNOTSUPP;
xfs_ilock(ip, iolock);
error = xfs_break_layouts(inode, &iolock);
error = xfs_break_layouts(inode, &iolock, BREAK_UNMAP);
if (error)
goto out_unlock;

View File

@ -378,6 +378,20 @@ static inline void xfs_ifunlock(struct xfs_inode *ip)
#define XFS_ILOCK_DEP(flags) (((flags) & XFS_ILOCK_DEP_MASK) \
>> 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_UNMAP case to make sure the
* layout-holder has a consistent view of the file's extent map. While
* BREAK_WRITE breaks can be satisfied by recalling FL_LAYOUT leases,
* BREAK_UNMAP breaks additionally require waiting for busy dax-pages to
* go idle.
*/
enum layout_break_reason {
BREAK_WRITE,
BREAK_UNMAP,
};
/*
* 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
@ -443,6 +457,8 @@ enum xfs_prealloc_flags {
int xfs_update_prealloc_flags(struct xfs_inode *ip,
enum xfs_prealloc_flags flags);
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);

View File

@ -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_UNMAP);
if (error)
goto out_unlock;

View File

@ -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>
@ -1030,13 +1029,14 @@ 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_UNMAP);
if (error) {
xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
return error;

View File

@ -31,17 +31,17 @@
* 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));
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 +121,8 @@ 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);

View File

@ -9,10 +9,11 @@ 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)
{
return 0;
}