[PATCH 3/3] xfs: refactor locking and unlocking two inodes against userspace IO

Darrick J. Wong
2020-06-23T04:03:56Z

From: Darrick J. Wong <darrick.wong@oracle.com>

Refactor the two functions that we use to lock and unlock two inodes to
block userspace from initiating IO against a file, whether via system
calls or mmap activity. Move them to xfs_inode.c since this functionality
isn't specific to reflink anyway.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
fs/xfs/xfs_file.c | 2 +
fs/xfs/xfs_inode.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++++++
fs/xfs/xfs_inode.h | 3 ++
fs/xfs/xfs_reflink.c | 85 +---------------------------------------------
fs/xfs/xfs_reflink.h | 2 -
5 files changed, 99 insertions(+), 86 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index b375fae811f2..a32d1eeee0f7 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1065,7 +1065,7 @@ xfs_file_remap_range(
if (mp->m_flags & XFS_MOUNT_WSYNC)
xfs_log_force_inode(dest);
out_unlock:
- xfs_reflink_remap_unlock(file_in, file_out);
+ xfs_iunlock_io_mmap(src, dest);
if (ret)
trace_xfs_reflink_remap_range_error(dest, ret, _RET_IP_);
return remapped > 0 ? remapped : ret;
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 9aea7d68d8ab..b9c6d1cc64a9 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -3881,3 +3881,96 @@ xfs_log_force_inode(
return 0;
return xfs_log_force_lsn(ip->i_mount, lsn, XFS_LOG_SYNC, NULL);
}
+
+/*
+ * Grab the exclusive iolock for a data copy from src to dest, making sure to
+ * abide vfs locking order (lowest pointer value goes first) and breaking the
+ * layout leases before proceeding. The loop is needed because we cannot call
+ * the blocking break_layout() with the iolocks held, and therefore have to
+ * back out both locks.
+ */
+static int
+xfs_iolock_two_inodes_and_break_layout(
+ struct inode *src,
+ struct inode *dest)
+{
+ int error;
+
+ if (src > dest)
+ swap(src, dest);
+
+retry:
+ /* Wait to break both inodes' layouts before we start locking. */
+ error = break_layout(src, true);
+ if (error)
+ return error;
+ if (src != dest) {
+ error = break_layout(dest, true);
+ if (error)
+ return error;
+ }
+
+ /* Lock one inode and make sure nobody got in and leased it. */
+ inode_lock(src);
+ error = break_layout(src, false);
+ if (error) {
+ inode_unlock(src);
+ if (error == -EWOULDBLOCK)
+ goto retry;
+ return error;
+ }
+
+ if (src == dest)
+ return 0;
+
+ /* Lock the other inode and make sure nobody got in and leased it. */
+ inode_lock_nested(dest, I_MUTEX_NONDIR2);
+ error = break_layout(dest, false);
+ if (error) {
+ inode_unlock(src);
+ inode_unlock(dest);
+ if (error == -EWOULDBLOCK)
+ goto retry;
+ return error;
+ }
+
+ return 0;
+}
+
+/*
+ * Lock two files so that userspace cannot initiate I/O via file syscalls or
+ * mmap activity.
+ */
+int
+xfs_ilock_io_mmap(
+ struct xfs_inode *ip1,
+ struct xfs_inode *ip2)
+{
+ int ret;
+
+ ret = xfs_iolock_two_inodes_and_break_layout(VFS_I(ip1), VFS_I(ip2));
+ if (ret)
+ return ret;
+ if (ip1 == ip2)
+ xfs_ilock(ip1, XFS_MMAPLOCK_EXCL);
+ else
+ xfs_lock_two_inodes(ip1, XFS_MMAPLOCK_EXCL,
+ ip2, XFS_MMAPLOCK_EXCL);
+ return 0;
+}
+
+/* Unlock both files to allow IO and mmap activity. */
+void
+xfs_iunlock_io_mmap(
+ struct xfs_inode *ip1,
+ struct xfs_inode *ip2)
+{
+ bool same_inode = (ip1 == ip2);
+
+ xfs_iunlock(ip2, XFS_MMAPLOCK_EXCL);
+ if (!same_inode)
+ xfs_iunlock(ip1, XFS_MMAPLOCK_EXCL);
+ inode_unlock(VFS_I(ip2));
+ if (!same_inode)
+ inode_unlock(VFS_I(ip1));
+}
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 47d3b391030d..001529784f96 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -499,4 +499,7 @@ void xfs_iunlink_destroy(struct xfs_perag *pag);

void xfs_end_io(struct work_struct *work);

+int xfs_ilock_io_mmap(struct xfs_inode *ip1, struct xfs_inode *ip2);
+void xfs_iunlock_io_mmap(struct xfs_inode *ip1, struct xfs_inode *ip2);
+
#endif /* __XFS_INODE_H__ */
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index dd9ed7d5694d..130b6be8180e 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1203,81 +1203,6 @@ xfs_reflink_remap_blocks(
return error;
}

-/*
- * Grab the exclusive iolock for a data copy from src to dest, making sure to
- * abide vfs locking order (lowest pointer value goes first) and breaking the
- * layout leases before proceeding. The loop is needed because we cannot call
- * the blocking break_layout() with the iolocks held, and therefore have to
- * back out both locks.
- */
-static int
-xfs_iolock_two_inodes_and_break_layout(
- struct inode *src,
- struct inode *dest)
-{
- int error;
-
- if (src > dest)
- swap(src, dest);
-
-retry:
- /* Wait to break both inodes' layouts before we start locking. */
- error = break_layout(src, true);
- if (error)
- return error;
- if (src != dest) {
- error = break_layout(dest, true);
- if (error)
- return error;
- }
-
- /* Lock one inode and make sure nobody got in and leased it. */
- inode_lock(src);
- error = break_layout(src, false);
- if (error) {
- inode_unlock(src);
- if (error == -EWOULDBLOCK)
- goto retry;
- return error;
- }
-
- if (src == dest)
- return 0;
-
- /* Lock the other inode and make sure nobody got in and leased it. */
- inode_lock_nested(dest, I_MUTEX_NONDIR2);
- error = break_layout(dest, false);
- if (error) {
- inode_unlock(src);
- inode_unlock(dest);
- if (error == -EWOULDBLOCK)
- goto retry;
- return error;
- }
-
- return 0;
-}
-
-/* Unlock both inodes after they've been prepped for a range clone. */
-void
-xfs_reflink_remap_unlock(
- struct file *file_in,
- struct file *file_out)
-{
- struct inode *inode_in = file_inode(file_in);
- struct xfs_inode *src = XFS_I(inode_in);
- struct inode *inode_out = file_inode(file_out);
- struct xfs_inode *dest = XFS_I(inode_out);
- bool same_inode = (inode_in == inode_out);
-
- xfs_iunlock(dest, XFS_MMAPLOCK_EXCL);
- if (!same_inode)
- xfs_iunlock(src, XFS_MMAPLOCK_EXCL);
- inode_unlock(inode_out);
- if (!same_inode)
- inode_unlock(inode_in);
-}
-
/*
* If we're reflinking to a point past the destination file's EOF, we must
* zero any speculative post-EOF preallocations that sit between the old EOF
@@ -1340,18 +1265,12 @@ xfs_reflink_remap_prep(
struct xfs_inode *src = XFS_I(inode_in);
struct inode *inode_out = file_inode(file_out);
struct xfs_inode *dest = XFS_I(inode_out);
- bool same_inode = (inode_in == inode_out);
int ret;

/* Lock both files against IO */
- ret = xfs_iolock_two_inodes_and_break_layout(inode_in, inode_out);
+ ret = xfs_ilock_io_mmap(src, dest);
if (ret)
return ret;
- if (same_inode)
- xfs_ilock(src, XFS_MMAPLOCK_EXCL);
- else
- xfs_lock_two_inodes(src, XFS_MMAPLOCK_EXCL, dest,
- XFS_MMAPLOCK_EXCL);

/* Check file eligibility and prepare for block sharing. */
ret = -EINVAL;
@@ -1402,7 +1321,7 @@ xfs_reflink_remap_prep(

return 0;
out_unlock:
- xfs_reflink_remap_unlock(file_in, file_out);
+ xfs_iunlock_io_mmap(src, dest);
return ret;
}

diff --git a/fs/xfs/xfs_reflink.h b/fs/xfs/xfs_reflink.h
index 3e4fd46373ab..487b00434b96 100644
--- a/fs/xfs/xfs_reflink.h
+++ b/fs/xfs/xfs_reflink.h
@@ -56,7 +56,5 @@ extern int xfs_reflink_remap_blocks(struct xfs_inode *src, loff_t pos_in,
loff_t *remapped);
extern int xfs_reflink_update_dest(struct xfs_inode *dest, xfs_off_t newlen,
xfs_extlen_t cowextsize, unsigned int remap_flags);
-extern void xfs_reflink_remap_unlock(struct file *file_in,
- struct file *file_out);

#endif /* __XFS_REFLINK_H */