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Subject[PATCH RFC 09/10] fs/xfs: Fail truncate if pages are GUP pinned
Date
From: Ira Weiny <ira.weiny@intel.com>

If pages are actively gup pinned fail the truncate operation. To
support an application who wishes to removing a pin upon SIGIO reception
we must change the order of breaking layout leases with respect to DAX
layout leases.

Check for a GUP pin on the page being truncated and return ETXTBSY if it
is GUP pinned.

Change the order of XFS break leased layouts and break DAX layouts.

Select EXPORT_BLOCK_OPS for FS_DAX to ensure that
xfs_break_lease_layouts() is defined for FS_DAX as well as pNFS.

Update comment for xfs_break_lease_layouts()

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
fs/Kconfig | 1 +
fs/xfs/xfs_file.c | 8 ++++++--
fs/xfs/xfs_pnfs.c | 14 +++++++-------
3 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/fs/Kconfig b/fs/Kconfig
index f1046cf6ad85..c54b0b88abbf 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -49,6 +49,7 @@ config FS_DAX
select DEV_PAGEMAP_OPS if (ZONE_DEVICE && !FS_DAX_LIMITED)
select FS_IOMAP
select DAX
+ select EXPORTFS_BLOCK_OPS
help
Direct Access (DAX) can be used on memory-backed block devices.
If the block device supports DAX and the filesystem supports DAX,
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 350eb5546d36..1dc61c98f7cd 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -756,6 +756,9 @@ xfs_break_dax_layouts(
if (!page)
return 0;

+ if (page_gup_pinned(page))
+ return -ETXTBSY;
+
*retry = true;
return ___wait_var_event(&page->_refcount,
atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE,
@@ -779,10 +782,11 @@ xfs_break_layouts(
retry = false;
switch (reason) {
case BREAK_UNMAP:
- error = xfs_break_dax_layouts(inode, &retry, off, len);
+ error = xfs_break_leased_layouts(inode, iolock, &retry);
if (error || retry)
break;
- /* fall through */
+ error = xfs_break_dax_layouts(inode, &retry, off, len);
+ break;
case BREAK_WRITE:
error = xfs_break_leased_layouts(inode, iolock, &retry);
break;
diff --git a/fs/xfs/xfs_pnfs.c b/fs/xfs/xfs_pnfs.c
index bde2c9f56a46..e70d24d12cbf 100644
--- a/fs/xfs/xfs_pnfs.c
+++ b/fs/xfs/xfs_pnfs.c
@@ -21,14 +21,14 @@
#include "xfs_pnfs.h"

/*
- * Ensure that we do not have any outstanding pNFS layouts that can be used by
- * clients to directly read from or write to this inode. This must be called
- * before every operation that can remove blocks from the extent map.
- * Additionally we call it during the write operation, where aren't concerned
- * about exposing unallocated blocks but just want to provide basic
+ * Ensure that we do not have any outstanding pNFS or longterm GUP layouts that
+ * can be used by clients to directly read from or write to this inode. This
+ * must be called before every operation that can remove blocks from the extent
+ * map. Additionally we call it during the write operation, where aren't
+ * concerned about exposing unallocated blocks but just want to provide basic
* synchronization between a local writer and pNFS clients. mmap writes would
- * also benefit from this sort of synchronization, but due to the tricky locking
- * rules in the page fault path we don't bother.
+ * also benefit from this sort of synchronization, but due to the tricky
+ * locking rules in the page fault path we don't bother.
*/
int
xfs_break_leased_layouts(
--
2.20.1
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