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xfs: support for synchronous DAX faults 

Return IOMAP_F_DIRTY from xfs_file_iomap_begin() when asked to prepare
blocks for writing and the inode is pinned, and has dirty fields other
than the timestamps.  In __xfs_filemap_fault() we then detect this case
and call dax_finish_sync_fault() to make sure all metadata is committed,
and to insert the page table entry.

Note that this will also dirty corresponding radix tree entry which is
what we want - fsync(2) will still provide data integrity guarantees for
applications not using userspace flushing. And applications using
userspace flushing can avoid calling fsync(2) and thus avoid the
performance overhead.

[JK: Added VM_SYNC flag handling]

Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Christoph Hellwig 2017-11-01 16:36:47 +01:00 committed by Dan Williams
parent 7b565c9f96
commit a39e596baa
2 changed files with 19 additions and 1 deletions
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15
fs/xfs/xfs_file.c
View File

@ -44,6 +44,7 @@
#include <linux/falloc.h>
#include <linux/pagevec.h>
#include <linux/backing-dev.h>
#include <linux/mman.h>
static const struct vm_operations_struct xfs_file_vm_ops;
@ -1040,7 +1041,11 @@ __xfs_filemap_fault(
xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
if (IS_DAX(inode)) {
ret = dax_iomap_fault(vmf, pe_size, NULL, &xfs_iomap_ops);
pfn_t pfn;
ret = dax_iomap_fault(vmf, pe_size, &pfn, &xfs_iomap_ops);
if (ret & VM_FAULT_NEEDDSYNC)
ret = dax_finish_sync_fault(vmf, pe_size, pfn);
} else {
if (write_fault)
ret = iomap_page_mkwrite(vmf, &xfs_iomap_ops);
@ -1110,6 +1115,13 @@ xfs_file_mmap(
struct file *filp,
struct vm_area_struct *vma)
{
/*
* We don't support synchronous mappings for non-DAX files. At least
* until someone comes with a sensible use case.
*/
if (!IS_DAX(file_inode(filp)) && (vma->vm_flags & VM_SYNC))
return -EOPNOTSUPP;
file_accessed(filp);
vma->vm_ops = &xfs_file_vm_ops;
if (IS_DAX(file_inode(filp)))
@ -1128,6 +1140,7 @@ const struct file_operations xfs_file_operations = {
.compat_ioctl = xfs_file_compat_ioctl,
#endif
.mmap = xfs_file_mmap,
.mmap_supported_flags = MAP_SYNC,
.open = xfs_file_open,
.release = xfs_file_release,
.fsync = xfs_file_fsync,

5
fs/xfs/xfs_iomap.c
View File

@ -33,6 +33,7 @@
#include "xfs_error.h"
#include "xfs_trans.h"
#include "xfs_trans_space.h"
#include "xfs_inode_item.h"
#include "xfs_iomap.h"
#include "xfs_trace.h"
#include "xfs_icache.h"
@ -1086,6 +1087,10 @@ xfs_file_iomap_begin(
trace_xfs_iomap_found(ip, offset, length, 0, &imap);
}
if ((flags & IOMAP_WRITE) && xfs_ipincount(ip) &&
(ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
iomap->flags |= IOMAP_F_DIRTY;
xfs_bmbt_to_iomap(ip, iomap, &imap);
if (shared)