xfs: remove i_iolock and use i_rwsem in the VFS inode instead

This patch drops the XFS-own i_iolock and uses the VFS i_rwsem which
recently replaced i_mutex instead.  This means we only have to take
one lock instead of two in many fast path operations, and we can
also shrink the xfs_inode structure.  Thanks to the xfs_ilock family
there is very little churn, the only thing of note is that we need
to switch to use the lock_two_directory helper for taking the i_rwsem
on two inodes in a few places to make sure our lock order matches
the one used in the VFS.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 23 insertions, 56 deletions

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index d818c160451f..d054b73b56fb 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -48,40 +48,6 @@
 static const struct vm_operations_struct xfs_file_vm_ops;
 
 /*
- * Locking primitives for read and write IO paths to ensure we consistently use
- * and order the inode->i_mutex, ip->i_lock and ip->i_iolock.
- */
-static inline void
-xfs_rw_ilock(
-        struct xfs_inode        *ip,
-        int                     type)
-{
-        if (type & XFS_IOLOCK_EXCL)
-                inode_lock(VFS_I(ip));
-        xfs_ilock(ip, type);
-}
-
-static inline void
-xfs_rw_iunlock(
-        struct xfs_inode        *ip,
-        int                     type)
-{
-        xfs_iunlock(ip, type);
-        if (type & XFS_IOLOCK_EXCL)
-                inode_unlock(VFS_I(ip));
-}
-
-static inline void
-xfs_rw_ilock_demote(
-        struct xfs_inode        *ip,
-        int                     type)
-{
-        xfs_ilock_demote(ip, type);
-        if (type & XFS_IOLOCK_EXCL)
-                inode_unlock(VFS_I(ip));
-}
-
-/*
  * Clear the specified ranges to zero through either the pagecache or DAX.
  * Holes and unwritten extents will be left as-is as they already are zeroed.
  */
@@ -273,7 +239,7 @@ xfs_file_dio_aio_read(
 
         file_accessed(iocb->ki_filp);
 
-        xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
+        xfs_ilock(ip, XFS_IOLOCK_SHARED);
         if (mapping->nrpages) {
                 ret = filemap_write_and_wait_range(mapping, iocb->ki_pos, end);
                 if (ret)
@@ -299,7 +265,7 @@ xfs_file_dio_aio_read(
         }
 
 out_unlock:
-        xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
+        xfs_iunlock(ip, XFS_IOLOCK_SHARED);
         return ret;
 }
 
@@ -317,9 +283,9 @@ xfs_file_dax_read(
         if (!count)
                 return 0; /* skip atime */
 
-        xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
+        xfs_ilock(ip, XFS_IOLOCK_SHARED);
         ret = dax_iomap_rw(iocb, to, &xfs_iomap_ops);
-        xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
+        xfs_iunlock(ip, XFS_IOLOCK_SHARED);
 
         file_accessed(iocb->ki_filp);
         return ret;
@@ -335,9 +301,9 @@ xfs_file_buffered_aio_read(
 
         trace_xfs_file_buffered_read(ip, iov_iter_count(to), iocb->ki_pos);
 
-        xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
+        xfs_ilock(ip, XFS_IOLOCK_SHARED);
         ret = generic_file_read_iter(iocb, to);
-        xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
+        xfs_iunlock(ip, XFS_IOLOCK_SHARED);
 
         return ret;
 }
@@ -418,15 +384,18 @@ restart:
         if (error <= 0)
                 return error;
 
-        error = xfs_break_layouts(inode, iolock, true);
+        error = xfs_break_layouts(inode, iolock);
         if (error)
                 return error;
 
-        /* For changing security info in file_remove_privs() we need i_mutex */
+        /*
+         * For changing security info in file_remove_privs() we need i_rwsem
+         * exclusively.
+         */
         if (*iolock == XFS_IOLOCK_SHARED && !IS_NOSEC(inode)) {
-                xfs_rw_iunlock(ip, *iolock);
+                xfs_iunlock(ip, *iolock);
                 *iolock = XFS_IOLOCK_EXCL;
-                xfs_rw_ilock(ip, *iolock);
+                xfs_ilock(ip, *iolock);
                 goto restart;
         }
         /*
@@ -451,9 +420,9 @@ restart:
                 spin_unlock(&ip->i_flags_lock);
                 if (!drained_dio) {
                         if (*iolock == XFS_IOLOCK_SHARED) {
-                                xfs_rw_iunlock(ip, *iolock);
+                                xfs_iunlock(ip, *iolock);
                                 *iolock = XFS_IOLOCK_EXCL;
-                                xfs_rw_ilock(ip, *iolock);
+                                xfs_ilock(ip, *iolock);
                                 iov_iter_reexpand(from, count);
                         }
                         /*
@@ -559,7 +528,7 @@ xfs_file_dio_aio_write(
                 iolock = XFS_IOLOCK_SHARED;
         }
 
-        xfs_rw_ilock(ip, iolock);
+        xfs_ilock(ip, iolock);
 
         ret = xfs_file_aio_write_checks(iocb, from, &iolock);
         if (ret)
@@ -591,7 +560,7 @@ xfs_file_dio_aio_write(
         if (unaligned_io)
                 inode_dio_wait(inode);
         else if (iolock == XFS_IOLOCK_EXCL) {
-                xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
+                xfs_ilock_demote(ip, XFS_IOLOCK_EXCL);
                 iolock = XFS_IOLOCK_SHARED;
         }
 
@@ -621,7 +590,7 @@ xfs_file_dio_aio_write(
                 iov_iter_advance(from, ret);
         }
 out:
-        xfs_rw_iunlock(ip, iolock);
+        xfs_iunlock(ip, iolock);
 
         /*
          * No fallback to buffered IO on errors for XFS, direct IO will either
@@ -643,7 +612,7 @@ xfs_file_dax_write(
         size_t                  count;
         loff_t                  pos;
 
-        xfs_rw_ilock(ip, iolock);
+        xfs_ilock(ip, iolock);
         ret = xfs_file_aio_write_checks(iocb, from, &iolock);
         if (ret)
                 goto out;
@@ -652,15 +621,13 @@ xfs_file_dax_write(
         count = iov_iter_count(from);
 
         trace_xfs_file_dax_write(ip, count, pos);
-
         ret = dax_iomap_rw(iocb, from, &xfs_iomap_ops);
         if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
                 i_size_write(inode, iocb->ki_pos);
                 error = xfs_setfilesize(ip, pos, ret);
         }
-
 out:
-        xfs_rw_iunlock(ip, iolock);
+        xfs_iunlock(ip, iolock);
         return error ? error : ret;
 }
 
@@ -677,7 +644,7 @@ xfs_file_buffered_aio_write(
         int                     enospc = 0;
         int                     iolock = XFS_IOLOCK_EXCL;
 
-        xfs_rw_ilock(ip, iolock);
+        xfs_ilock(ip, iolock);
 
         ret = xfs_file_aio_write_checks(iocb, from, &iolock);
         if (ret)
@@ -721,7 +688,7 @@ write_retry:
 
         current->backing_dev_info = NULL;
 out:
-        xfs_rw_iunlock(ip, iolock);
+        xfs_iunlock(ip, iolock);
         return ret;
 }
 
@@ -797,7 +764,7 @@ xfs_file_fallocate(
                 return -EOPNOTSUPP;
 
         xfs_ilock(ip, iolock);
-        error = xfs_break_layouts(inode, &iolock, false);
+        error = xfs_break_layouts(inode, &iolock);
         if (error)
                 goto out_unlock;