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>

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 35309bd..4774c71 100644 (file)
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -312,7 +312,7 @@ restart:
        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 @@ buffered:
        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;
 

diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 1eebc53..e5b8498 100644 (file)
--- 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 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
  * new subdirectory gets S_ISGID bit from parent.
@@ -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);

diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 4151fad..91e73d6 100644 (file)
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -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;
 

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 138fb36..ce0c1f9 100644 (file)
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -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;

diff --git a/fs/xfs/xfs_pnfs.c b/fs/xfs/xfs_pnfs.c
index 6ea7b0b..f44c359 100644 (file)
--- a/fs/xfs/xfs_pnfs.c
+++ b/fs/xfs/xfs_pnfs.c
@@ -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);
 

diff --git a/fs/xfs/xfs_pnfs.h b/fs/xfs/xfs_pnfs.h
index bf45951..940c6c2 100644 (file)
--- a/fs/xfs/xfs_pnfs.h
+++ b/fs/xfs/xfs_pnfs.h
@@ -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;
 }