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Subject[PATCH v6 14/15] xfs: prepare xfs_break_layouts() for another layout type
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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_TRUNCATE 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_TRUNCATE 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_TRUNCATE breaks additionally
require waiting for busy dax-pages to go idle.

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 | 23 +++++++++++++++++------
fs/xfs/xfs_inode.h | 18 ++++++++++++++++--
fs/xfs/xfs_ioctl.c | 2 +-
fs/xfs/xfs_iops.c | 5 +++--
4 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 5742d395a4e4..399c5221f101 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -352,7 +352,7 @@ xfs_file_aio_write_checks(

xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
*iolock |= XFS_MMAPLOCK_EXCL;
- error = xfs_break_layouts(inode, iolock);
+ error = xfs_break_layouts(inode, iolock, BREAK_WRITE);
if (error) {
*iolock &= ~XFS_MMAPLOCK_EXCL;
xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
@@ -762,7 +762,8 @@ xfs_file_write_iter(
int
xfs_break_layouts(
struct inode *inode,
- uint *iolock)
+ uint *iolock,
+ enum layout_break_reason reason)
{
struct xfs_inode *ip = XFS_I(inode);
int ret;
@@ -770,9 +771,19 @@ xfs_break_layouts(
ASSERT(xfs_isilocked(ip, XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL
| XFS_MMAPLOCK_EXCL));

- ret = xfs_break_leased_layouts(inode, iolock);
- if (ret > 0)
- ret = 0;
+ switch (reason) {
+ case BREAK_TRUNCATE:
+ /* fall through */
+ case BREAK_WRITE:
+ ret = xfs_break_leased_layouts(inode, iolock);
+ if (ret > 0)
+ ret = 0;
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
return ret;
}

@@ -802,7 +813,7 @@ xfs_file_fallocate(
return -EOPNOTSUPP;

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

diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 74c63f3a720f..1a66c7afcf45 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_TRUNCATE 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_TRUNCATE breaks additionally require waiting for busy dax-pages
+ * to go idle.
+ */
+enum layout_break_reason {
+ BREAK_WRITE,
+ BREAK_TRUNCATE,
+};
+
+/*
* 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.
@@ -447,8 +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);
-
+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 d70a1919e787..847a67186d95 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -643,7 +643,7 @@ xfs_ioc_space(
return error;

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

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 78eb56d447df..f9fcadb5b555 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1026,13 +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_TRUNCATE);
if (error) {
xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
return error;
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