[PATCH v8 17/18] xfs: prepare xfs_break_layouts() for another layout type

[Dan Williams]

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 
Cc: "Darrick J. Wong" 
Reported-by: Dave Chinner 
Reported-by: Christoph Hellwig 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Dan Williams 
---
 fs/xfs/xfs_file.c  |   30 --
 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, 59 insertions(+), 15 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 18edf04811d0..51e6506bdcb1 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 +752,32 @@ xfs_file_write_iter(
return ret;
 }
 
+int
+xfs_break_layouts(
+   struct inode*inode,
+   uint*iolock,
+   enum layout_break_reason reason)
+{
+   boolretry = false;
+   int error = 0;
+
+   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:
+   error = xfs_break_leased_layouts(inode, iolock, );
+   break;
+   default:
+   WARN_ON_ONCE(1);
+   return -EINVAL;
+   }
+
+   return error;
+}
+
 #defineXFS_FALLOC_FL_SUPPORTED 
\
(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |   \
 FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE |  \
@@ -778,7 +804,7 @@ xfs_file_fallocate(
return -EOPNOTSUPP;
 
xfs_ilock(ip, iolock);
-   error = xfs_break_layouts(inode, );
+   error = xfs_break_layouts(inode, , BREAK_UNMAP);
if (error)
goto out_unlock;
 
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 3e8dc990d41c..7e1a077dfc04 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_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.
+ */
+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
  * 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);
 intxfs_zero_range(struct xfs_inode *ip, xfs_off_t pos, xfs_off_t count,
bool *did_zero);
+intxfs_break_layouts(struct inode *inode, uint *iolock,
+   enum layout_break_reason reason);
 
 /* from xfs_iops.c */
 extern void xfs_setup_inode(struct 

[PATCH v8 17/18] xfs: prepare xfs_break_layouts() for another layout type

[Dan Williams]

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 
Cc: "Darrick J. Wong" 
Reported-by: Dave Chinner 
Reported-by: Christoph Hellwig 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Dan Williams 
---
 fs/xfs/xfs_file.c  |   30 --
 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, 59 insertions(+), 15 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 18edf04811d0..51e6506bdcb1 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 +752,32 @@ xfs_file_write_iter(
return ret;
 }
 
+int
+xfs_break_layouts(
+   struct inode*inode,
+   uint*iolock,
+   enum layout_break_reason reason)
+{
+   boolretry = false;
+   int error = 0;
+
+   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:
+   error = xfs_break_leased_layouts(inode, iolock, );
+   break;
+   default:
+   WARN_ON_ONCE(1);
+   return -EINVAL;
+   }
+
+   return error;
+}
+
 #defineXFS_FALLOC_FL_SUPPORTED 
\
(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |   \
 FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE |  \
@@ -778,7 +804,7 @@ xfs_file_fallocate(
return -EOPNOTSUPP;
 
xfs_ilock(ip, iolock);
-   error = xfs_break_layouts(inode, );
+   error = xfs_break_layouts(inode, , BREAK_UNMAP);
if (error)
goto out_unlock;
 
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 3e8dc990d41c..7e1a077dfc04 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_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.
+ */
+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
  * 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);
 intxfs_zero_range(struct xfs_inode *ip, xfs_off_t pos, xfs_off_t count,
bool *did_zero);
+intxfs_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..91e73d663099 100644
--- a/fs/xfs/xfs_ioctl.c