xfs: don't allocate an ioend for direct I/O completions

Back in the days when the direct I/O ->end_io callback could be called
from interrupt context for AIO we needed a structure to hand off to the
workqueue, and reused the ioend structure for this purpose.  These days
->end_io is always called from user or workqueue context, which allows us
to avoid this memory allocation and simplify the code significantly.

[dchinner: removed now unused xfs_finish_ioend_sync() function after
	   Brian Foster did an initial review. ]

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

2 files changed, 61 insertions, 91 deletions

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 18e2f3bbae5e..3a9b7a1b8704 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -135,30 +135,22 @@ xfs_setfilesize_trans_alloc(
  */
 STATIC int
 xfs_setfilesize(
-        struct xfs_ioend        *ioend)
+        struct xfs_inode        *ip,
+        struct xfs_trans        *tp,
+        xfs_off_t               offset,
+        size_t                  size)
 {
-        struct xfs_inode        *ip = XFS_I(ioend->io_inode);
-        struct xfs_trans        *tp = ioend->io_append_trans;
         xfs_fsize_t             isize;
 
-        /*
-         * The transaction may have been allocated in the I/O submission thread,
-         * thus we need to mark ourselves as beeing in a transaction manually.
-         * Similarly for freeze protection.
-         */
-        current_set_flags_nested(&tp->t_pflags, PF_FSTRANS);
-        rwsem_acquire_read(&VFS_I(ip)->i_sb->s_writers.lock_map[SB_FREEZE_FS-1],
-                           0, 1, _THIS_IP_);
-
         xfs_ilock(ip, XFS_ILOCK_EXCL);
-        isize = xfs_new_eof(ip, ioend->io_offset + ioend->io_size);
+        isize = xfs_new_eof(ip, offset + size);
         if (!isize) {
                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
                 xfs_trans_cancel(tp, 0);
                 return 0;
         }
 
-        trace_xfs_setfilesize(ip, ioend->io_offset, ioend->io_size);
+        trace_xfs_setfilesize(ip, offset, size);
 
         ip->i_d.di_size = isize;
         xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
@@ -167,6 +159,25 @@ xfs_setfilesize(
         return xfs_trans_commit(tp, 0);
 }
 
+STATIC int
+xfs_setfilesize_ioend(
+        struct xfs_ioend        *ioend)
+{
+        struct xfs_inode        *ip = XFS_I(ioend->io_inode);
+        struct xfs_trans        *tp = ioend->io_append_trans;
+
+        /*
+         * The transaction may have been allocated in the I/O submission thread,
+         * thus we need to mark ourselves as being in a transaction manually.
+         * Similarly for freeze protection.
+         */
+        current_set_flags_nested(&tp->t_pflags, PF_FSTRANS);
+        rwsem_acquire_read(&VFS_I(ip)->i_sb->s_writers.lock_map[SB_FREEZE_FS-1],
+                           0, 1, _THIS_IP_);
+
+        return xfs_setfilesize(ip, tp, ioend->io_offset, ioend->io_size);
+}
+
 /*
  * Schedule IO completion handling on the final put of an ioend.
  *
@@ -182,8 +193,7 @@ xfs_finish_ioend(
 
                 if (ioend->io_type == XFS_IO_UNWRITTEN)
                         queue_work(mp->m_unwritten_workqueue, &ioend->io_work);
-                else if (ioend->io_append_trans ||
-                         (ioend->io_isdirect && xfs_ioend_is_append(ioend)))
+                else if (ioend->io_append_trans)
                         queue_work(mp->m_data_workqueue, &ioend->io_work);
                 else
                         xfs_destroy_ioend(ioend);
@@ -215,22 +225,8 @@ xfs_end_io(
         if (ioend->io_type == XFS_IO_UNWRITTEN) {
                 error = xfs_iomap_write_unwritten(ip, ioend->io_offset,
                                                   ioend->io_size);
-        } else if (ioend->io_isdirect && xfs_ioend_is_append(ioend)) {
-                /*
-                 * For direct I/O we do not know if we need to allocate blocks
-                 * or not so we can't preallocate an append transaction as that
-                 * results in nested reservations and log space deadlocks. Hence
-                 * allocate the transaction here. While this is sub-optimal and
-                 * can block IO completion for some time, we're stuck with doing
-                 * it this way until we can pass the ioend to the direct IO
-                 * allocation callbacks and avoid nesting that way.
-                 */
-                error = xfs_setfilesize_trans_alloc(ioend);
-                if (error)
-                        goto done;
-                error = xfs_setfilesize(ioend);
         } else if (ioend->io_append_trans) {
-                error = xfs_setfilesize(ioend);
+                error = xfs_setfilesize_ioend(ioend);
         } else {
                 ASSERT(!xfs_ioend_is_append(ioend));
         }
@@ -242,17 +238,6 @@ done:
 }
 
 /*
- * Call IO completion handling in caller context on the final put of an ioend.
- */
-STATIC void
-xfs_finish_ioend_sync(
-        struct xfs_ioend        *ioend)
-{
-        if (atomic_dec_and_test(&ioend->io_remaining))
-                xfs_end_io(&ioend->io_work);
-}
-
-/*
  * Allocate and initialise an IO completion structure.
  * We need to track unwritten extent write completion here initially.
  * We'll need to extend this for updating the ondisk inode size later
@@ -273,7 +258,6 @@ xfs_alloc_ioend(
          * all the I/O from calling the completion routine too early.
          */
         atomic_set(&ioend->io_remaining, 1);
-        ioend->io_isdirect = 0;
         ioend->io_error = 0;
         ioend->io_list = NULL;
         ioend->io_type = type;
@@ -1459,11 +1443,7 @@ xfs_get_blocks_direct(
  *
  * If the private argument is non-NULL __xfs_get_blocks signals us that we
  * need to issue a transaction to convert the range from unwritten to written
- * extents.  In case this is regular synchronous I/O we just call xfs_end_io
- * to do this and we are done.  But in case this was a successful AIO
- * request this handler is called from interrupt context, from which we
- * can't start transactions.  In that case offload the I/O completion to
- * the workqueues we also use for buffered I/O completion.
+ * extents.
  */
 STATIC void
 xfs_end_io_direct_write(
@@ -1472,7 +1452,12 @@ xfs_end_io_direct_write(
         ssize_t                 size,
         void                    *private)
 {
-        struct xfs_ioend        *ioend = iocb->private;
+        struct inode            *inode = file_inode(iocb->ki_filp);
+        struct xfs_inode        *ip = XFS_I(inode);
+        struct xfs_mount        *mp = ip->i_mount;
+
+        if (XFS_FORCED_SHUTDOWN(mp))
+                return;
 
         /*
          * While the generic direct I/O code updates the inode size, it does
@@ -1480,22 +1465,33 @@ xfs_end_io_direct_write(
          * end_io handler thinks the on-disk size is outside the in-core
          * size.  To prevent this just update it a little bit earlier here.
          */
-        if (offset + size > i_size_read(ioend->io_inode))
-                i_size_write(ioend->io_inode, offset + size);
+        if (offset + size > i_size_read(inode))
+                i_size_write(inode, offset + size);
 
         /*
-         * blockdev_direct_IO can return an error even after the I/O
-         * completion handler was called.  Thus we need to protect
-         * against double-freeing.
+         * For direct I/O we do not know if we need to allocate blocks or not,
+         * so we can't preallocate an append transaction, as that results in
+         * nested reservations and log space deadlocks. Hence allocate the
+         * transaction here. While this is sub-optimal and can block IO
+         * completion for some time, we're stuck with doing it this way until
+         * we can pass the ioend to the direct IO allocation callbacks and
+         * avoid nesting that way.
          */
-        iocb->private = NULL;
-
-        ioend->io_offset = offset;
-        ioend->io_size = size;
-        if (private && size > 0)
-                ioend->io_type = XFS_IO_UNWRITTEN;
+        if (private && size > 0) {
+                xfs_iomap_write_unwritten(ip, offset, size);
+        } else if (offset + size > ip->i_d.di_size) {
+                struct xfs_trans        *tp;
+                int                     error;
+
+                tp = xfs_trans_alloc(mp, XFS_TRANS_FSYNC_TS);
+                error = xfs_trans_reserve(tp, &M_RES(mp)->tr_fsyncts, 0, 0);
+                if (error) {
+                        xfs_trans_cancel(tp, 0);
+                        return;
+                }
 
-        xfs_finish_ioend_sync(ioend);
+                xfs_setfilesize(ip, tp, offset, size);
+        }
 }
 
 STATIC ssize_t
@@ -1507,39 +1503,16 @@ xfs_vm_direct_IO(
 {
         struct inode            *inode = iocb->ki_filp->f_mapping->host;
         struct block_device     *bdev = xfs_find_bdev_for_inode(inode);
-        struct xfs_ioend        *ioend = NULL;
-        ssize_t                 ret;
 
         if (rw & WRITE) {
-                size_t size = iov_iter_count(iter);
-
-                /*
-                 * We cannot preallocate a size update transaction here as we
-                 * don't know whether allocation is necessary or not. Hence we
-                 * can only tell IO completion that one is necessary if we are
-                 * not doing unwritten extent conversion.
-                 */
-                iocb->private = ioend = xfs_alloc_ioend(inode, XFS_IO_DIRECT);
-                if (offset + size > XFS_I(inode)->i_d.di_size)
-                        ioend->io_isdirect = 1;
-
-                ret = __blockdev_direct_IO(rw, iocb, inode, bdev, iter,
+                return __blockdev_direct_IO(rw, iocb, inode, bdev, iter,
                                             offset, xfs_get_blocks_direct,
                                             xfs_end_io_direct_write, NULL,
                                             DIO_ASYNC_EXTEND);
-                if (ret != -EIOCBQUEUED && iocb->private)
-                        goto out_destroy_ioend;
-        } else {
-                ret = __blockdev_direct_IO(rw, iocb, inode, bdev, iter,
-                                            offset, xfs_get_blocks_direct,
-                                            NULL, NULL, 0);
         }
-
-        return ret;
-
-out_destroy_ioend:
-        xfs_destroy_ioend(ioend);
-        return ret;
+        return __blockdev_direct_IO(rw, iocb, inode, bdev, iter,
+                                    offset, xfs_get_blocks_direct,
+                                    NULL, NULL, 0);
 }
 
 /*
diff --git a/fs/xfs/xfs_aops.h b/fs/xfs/xfs_aops.h
index f94dd459dff9..ac644e0137a4 100644
--- a/fs/xfs/xfs_aops.h
+++ b/fs/xfs/xfs_aops.h
@@ -24,14 +24,12 @@ extern mempool_t *xfs_ioend_pool;
  * Types of I/O for bmap clustering and I/O completion tracking.
  */
 enum {
-        XFS_IO_DIRECT = 0,      /* special case for direct I/O ioends */
         XFS_IO_DELALLOC,        /* covers delalloc region */
         XFS_IO_UNWRITTEN,       /* covers allocated but uninitialized data */
         XFS_IO_OVERWRITE,       /* covers already allocated extent */
 };
 
 #define XFS_IO_TYPES \
-        { 0,                    "" }, \
         { XFS_IO_DELALLOC,              "delalloc" }, \
         { XFS_IO_UNWRITTEN,             "unwritten" }, \
         { XFS_IO_OVERWRITE,             "overwrite" }
@@ -45,7 +43,6 @@ typedef struct xfs_ioend {
         unsigned int            io_type;        /* delalloc / unwritten */
         int                     io_error;       /* I/O error code */
         atomic_t                io_remaining;   /* hold count */
-        unsigned int            io_isdirect : 1;/* direct I/O */
         struct inode            *io_inode;      /* file being written to */
         struct buffer_head      *io_buffer_head;/* buffer linked list head */
         struct buffer_head      *io_buffer_tail;/* buffer linked list tail */