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Subject[RFC PATCH V2 08/12] fs/xfs: Add lock/unlock mode to xfs
Date
From: Ira Weiny <ira.weiny@intel.com>

XFS requires regular files to be locked while changing to/from DAX mode.

Define a new DAX lock type and implement the [un]lock_mode() inode
operation callbacks.

We define a new XFS_DAX_* lock type to carry the lock through the
transaction because we don't want to use IOLOCK as that would cause
performance issues with locking of the inode itself.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
fs/xfs/xfs_icache.c | 2 ++
fs/xfs/xfs_inode.c | 37 +++++++++++++++++++++++++++++++++++--
fs/xfs/xfs_inode.h | 12 ++++++++++--
fs/xfs/xfs_iops.c | 24 +++++++++++++++++++++++-
4 files changed, 70 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index 8dc2e5414276..0288672e8902 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -74,6 +74,8 @@ xfs_inode_alloc(
INIT_LIST_HEAD(&ip->i_ioend_list);
spin_lock_init(&ip->i_ioend_lock);

+ percpu_init_rwsem(&ip->i_dax_sem);
+
return ip;
}

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 401da197f012..e8fd95b75e5b 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -142,12 +142,12 @@ xfs_ilock_attr_map_shared(
*
* Basic locking order:
*
- * i_rwsem -> i_mmap_lock -> page_lock -> i_ilock
+ * i_rwsem -> i_dax_sem -> i_mmap_lock -> page_lock -> i_ilock
*
* mmap_sem locking order:
*
* i_rwsem -> page lock -> mmap_sem
- * mmap_sem -> i_mmap_lock -> page_lock
+ * mmap_sem -> i_dax_sem -> i_mmap_lock -> page_lock
*
* The difference in mmap_sem locking order mean that we cannot hold the
* i_mmap_lock over syscall based read(2)/write(2) based IO. These IO paths can
@@ -181,6 +181,13 @@ xfs_ilock(
ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
(XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_SUBCLASS_MASK)) == 0);
+ ASSERT((lock_flags & (XFS_DAX_SHARED | XFS_DAX_EXCL)) !=
+ (XFS_DAX_SHARED | XFS_DAX_EXCL));
+
+ if (lock_flags & XFS_DAX_EXCL)
+ percpu_down_write(&ip->i_dax_sem);
+ else if (lock_flags & XFS_DAX_SHARED)
+ percpu_down_read(&ip->i_dax_sem);

if (lock_flags & XFS_IOLOCK_EXCL) {
down_write_nested(&VFS_I(ip)->i_rwsem,
@@ -224,6 +231,8 @@ xfs_ilock_nowait(
* You can't set both SHARED and EXCL for the same lock,
* and only XFS_IOLOCK_SHARED, XFS_IOLOCK_EXCL, XFS_ILOCK_SHARED,
* and XFS_ILOCK_EXCL are valid values to set in lock_flags.
+ *
+ * XFS_DAX_* is not allowed
*/
ASSERT((lock_flags & (XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL)) !=
(XFS_IOLOCK_SHARED | XFS_IOLOCK_EXCL));
@@ -232,6 +241,7 @@ xfs_ilock_nowait(
ASSERT((lock_flags & (XFS_ILOCK_SHARED | XFS_ILOCK_EXCL)) !=
(XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_SUBCLASS_MASK)) == 0);
+ ASSERT((lock_flags & (XFS_DAX_SHARED | XFS_DAX_EXCL)) == 0);

if (lock_flags & XFS_IOLOCK_EXCL) {
if (!down_write_trylock(&VFS_I(ip)->i_rwsem))
@@ -302,6 +312,8 @@ xfs_iunlock(
(XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
ASSERT((lock_flags & ~(XFS_LOCK_MASK | XFS_LOCK_SUBCLASS_MASK)) == 0);
ASSERT(lock_flags != 0);
+ ASSERT((lock_flags & (XFS_DAX_SHARED | XFS_DAX_EXCL)) !=
+ (XFS_DAX_SHARED | XFS_DAX_EXCL));

if (lock_flags & XFS_IOLOCK_EXCL)
up_write(&VFS_I(ip)->i_rwsem);
@@ -318,6 +330,11 @@ xfs_iunlock(
else if (lock_flags & XFS_ILOCK_SHARED)
mrunlock_shared(&ip->i_lock);

+ if (lock_flags & XFS_DAX_EXCL)
+ percpu_up_write(&ip->i_dax_sem);
+ else if (lock_flags & XFS_DAX_SHARED)
+ percpu_up_read(&ip->i_dax_sem);
+
trace_xfs_iunlock(ip, lock_flags, _RET_IP_);
}

@@ -333,6 +350,8 @@ xfs_ilock_demote(
ASSERT(lock_flags & (XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL|XFS_ILOCK_EXCL));
ASSERT((lock_flags &
~(XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL|XFS_ILOCK_EXCL)) == 0);
+ /* XFS_DAX_* is not allowed */
+ ASSERT((lock_flags & (XFS_DAX_SHARED | XFS_DAX_EXCL)) == 0);

if (lock_flags & XFS_ILOCK_EXCL)
mrdemote(&ip->i_lock);
@@ -369,6 +388,13 @@ xfs_isilocked(
return rwsem_is_locked(&VFS_I(ip)->i_rwsem);
}

+ if (lock_flags & (XFS_DAX_EXCL|XFS_DAX_SHARED)) {
+ if (!(lock_flags & XFS_DAX_SHARED))
+ return !debug_locks ||
+ percpu_rwsem_is_held(&ip->i_dax_sem, 0);
+ return rwsem_is_locked(&ip->i_dax_sem);
+ }
+
ASSERT(0);
return 0;
}
@@ -465,6 +491,9 @@ xfs_lock_inodes(
ASSERT(!(lock_mode & XFS_ILOCK_EXCL) ||
inodes <= XFS_ILOCK_MAX_SUBCLASS + 1);

+ /* XFS_DAX_* is not allowed */
+ ASSERT((lock_mode & (XFS_DAX_SHARED | XFS_DAX_EXCL)) == 0);
+
if (lock_mode & XFS_IOLOCK_EXCL) {
ASSERT(!(lock_mode & (XFS_MMAPLOCK_EXCL | XFS_ILOCK_EXCL)));
} else if (lock_mode & XFS_MMAPLOCK_EXCL)
@@ -566,6 +595,10 @@ xfs_lock_two_inodes(
ASSERT(!(ip0_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)) ||
!(ip1_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL)));

+ /* XFS_DAX_* is not allowed */
+ ASSERT((ip0_mode & (XFS_DAX_SHARED | XFS_DAX_EXCL)) == 0);
+ ASSERT((ip1_mode & (XFS_DAX_SHARED | XFS_DAX_EXCL)) == 0);
+
ASSERT(ip0->i_ino != ip1->i_ino);

if (ip0->i_ino > ip1->i_ino) {
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 492e53992fa9..693ca66bd89b 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -67,6 +67,9 @@ typedef struct xfs_inode {
spinlock_t i_ioend_lock;
struct work_struct i_ioend_work;
struct list_head i_ioend_list;
+
+ /* protect changing the mode to/from DAX */
+ struct percpu_rw_semaphore i_dax_sem;
} xfs_inode_t;

/* Convert from vfs inode to xfs inode */
@@ -278,10 +281,13 @@ static inline void xfs_ifunlock(struct xfs_inode *ip)
#define XFS_ILOCK_SHARED (1<<3)
#define XFS_MMAPLOCK_EXCL (1<<4)
#define XFS_MMAPLOCK_SHARED (1<<5)
+#define XFS_DAX_EXCL (1<<6)
+#define XFS_DAX_SHARED (1<<7)

#define XFS_LOCK_MASK (XFS_IOLOCK_EXCL | XFS_IOLOCK_SHARED \
| XFS_ILOCK_EXCL | XFS_ILOCK_SHARED \
- | XFS_MMAPLOCK_EXCL | XFS_MMAPLOCK_SHARED)
+ | XFS_MMAPLOCK_EXCL | XFS_MMAPLOCK_SHARED \
+ | XFS_DAX_EXCL | XFS_DAX_SHARED)

#define XFS_LOCK_FLAGS \
{ XFS_IOLOCK_EXCL, "IOLOCK_EXCL" }, \
@@ -289,7 +295,9 @@ static inline void xfs_ifunlock(struct xfs_inode *ip)
{ XFS_ILOCK_EXCL, "ILOCK_EXCL" }, \
{ XFS_ILOCK_SHARED, "ILOCK_SHARED" }, \
{ XFS_MMAPLOCK_EXCL, "MMAPLOCK_EXCL" }, \
- { XFS_MMAPLOCK_SHARED, "MMAPLOCK_SHARED" }
+ { XFS_MMAPLOCK_SHARED, "MMAPLOCK_SHARED" }, \
+ { XFS_DAX_EXCL, "DAX_EXCL" }, \
+ { XFS_DAX_SHARED, "DAX_SHARED" }


/*
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index d6843cdb51d0..a2f2604c3187 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1158,6 +1158,16 @@ xfs_vn_tmpfile(
return xfs_generic_create(dir, dentry, mode, 0, true);
}

+static void xfs_lock_mode(struct inode *inode)
+{
+ xfs_ilock(XFS_I(inode), XFS_DAX_SHARED);
+}
+
+static void xfs_unlock_mode(struct inode *inode)
+{
+ xfs_iunlock(XFS_I(inode), XFS_DAX_SHARED);
+}
+
static const struct inode_operations xfs_inode_operations = {
.get_acl = xfs_get_acl,
.set_acl = xfs_set_acl,
@@ -1168,6 +1178,18 @@ static const struct inode_operations xfs_inode_operations = {
.update_time = xfs_vn_update_time,
};

+static const struct inode_operations xfs_reg_inode_operations = {
+ .get_acl = xfs_get_acl,
+ .set_acl = xfs_set_acl,
+ .getattr = xfs_vn_getattr,
+ .setattr = xfs_vn_setattr,
+ .listxattr = xfs_vn_listxattr,
+ .fiemap = xfs_vn_fiemap,
+ .update_time = xfs_vn_update_time,
+ .lock_mode = xfs_lock_mode,
+ .unlock_mode = xfs_unlock_mode,
+};
+
static const struct inode_operations xfs_dir_inode_operations = {
.create = xfs_vn_create,
.lookup = xfs_vn_lookup,
@@ -1372,7 +1394,7 @@ xfs_setup_iops(

switch (inode->i_mode & S_IFMT) {
case S_IFREG:
- inode->i_op = &xfs_inode_operations;
+ inode->i_op = &xfs_reg_inode_operations;
inode->i_fop = &xfs_file_operations;
if (IS_DAX(inode))
inode->i_mapping->a_ops = &xfs_dax_aops;
--
2.21.0
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