Merge tag 'driver-core-3.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core update from Greg KH:
 "Here's the set of driver core patches for 3.19-rc1.

  They are dominated by the removal of the .owner field in platform
  drivers.  They touch a lot of files, but they are "simple" changes,
  just removing a line in a structure.

  Other than that, a few minor driver core and debugfs changes.  There
  are some ath9k patches coming in through this tree that have been
  acked by the wireless maintainers as they relied on the debugfs
  changes.

  Everything has been in linux-next for a while"

* tag 'driver-core-3.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (324 commits)
  Revert "ath: ath9k: use debugfs_create_devm_seqfile() helper for seq_file entries"
  fs: debugfs: add forward declaration for struct device type
  firmware class: Deletion of an unnecessary check before the function call "vunmap"
  firmware loader: fix hung task warning dump
  devcoredump: provide a one-way disable function
  device: Add dev_<level>_once variants
  ath: ath9k: use debugfs_create_devm_seqfile() helper for seq_file entries
  ath: use seq_file api for ath9k debugfs files
  debugfs: add helper function to create device related seq_file
  drivers/base: cacheinfo: remove noisy error boot message
  Revert "core: platform: add warning if driver has no owner"
  drivers: base: support cpu cache information interface to userspace via sysfs
  drivers: base: add cpu_device_create to support per-cpu devices
  topology: replace custom attribute macros with standard DEVICE_ATTR*
  cpumask: factor out show_cpumap into separate helper function
  driver core: Fix unbalanced device reference in drivers_probe
  driver core: fix race with userland in device_add()
  sysfs/kernfs: make read requests on pre-alloc files use the buffer.
  sysfs/kernfs: allow attributes to request write buffer be pre-allocated.
  fs: sysfs: return EGBIG on write if offset is larger than file size
  ...

1 files changed, 50 insertions, 23 deletions

diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 4429d6d9217f..697390ea47b8 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -106,7 +106,7 @@ static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
         const struct kernfs_ops *ops;
 
         /*
-         * @of->mutex nests outside active ref and is just to ensure that
+         * @of->mutex nests outside active ref and is primarily to ensure that
          * the ops aren't called concurrently for the same open file.
          */
         mutex_lock(&of->mutex);
@@ -189,13 +189,16 @@ static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
         const struct kernfs_ops *ops;
         char *buf;
 
-        buf = kmalloc(len, GFP_KERNEL);
+        buf = of->prealloc_buf;
+        if (!buf)
+                buf = kmalloc(len, GFP_KERNEL);
         if (!buf)
                 return -ENOMEM;
 
         /*
-         * @of->mutex nests outside active ref and is just to ensure that
-         * the ops aren't called concurrently for the same open file.
+         * @of->mutex nests outside active ref and is used both to ensure that
+         * the ops aren't called concurrently for the same open file, and
+         * to provide exclusive access to ->prealloc_buf (when that exists).
          */
         mutex_lock(&of->mutex);
         if (!kernfs_get_active(of->kn)) {
@@ -210,21 +213,22 @@ static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
         else
                 len = -EINVAL;
 
-        kernfs_put_active(of->kn);
-        mutex_unlock(&of->mutex);
-
         if (len < 0)
-                goto out_free;
+                goto out_unlock;
 
         if (copy_to_user(user_buf, buf, len)) {
                 len = -EFAULT;
-                goto out_free;
+                goto out_unlock;
         }
 
         *ppos += len;
 
+ out_unlock:
+        kernfs_put_active(of->kn);
+        mutex_unlock(&of->mutex);
  out_free:
-        kfree(buf);
+        if (buf != of->prealloc_buf)
+                kfree(buf);
         return len;
 }
 
@@ -278,19 +282,16 @@ static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
                 len = min_t(size_t, count, PAGE_SIZE);
         }
 
-        buf = kmalloc(len + 1, GFP_KERNEL);
+        buf = of->prealloc_buf;
+        if (!buf)
+                buf = kmalloc(len + 1, GFP_KERNEL);
         if (!buf)
                 return -ENOMEM;
 
-        if (copy_from_user(buf, user_buf, len)) {
-                len = -EFAULT;
-                goto out_free;
-        }
-        buf[len] = '\0';        /* guarantee string termination */
-
         /*
-         * @of->mutex nests outside active ref and is just to ensure that
-         * the ops aren't called concurrently for the same open file.
+         * @of->mutex nests outside active ref and is used both to ensure that
+         * the ops aren't called concurrently for the same open file, and
+         * to provide exclusive access to ->prealloc_buf (when that exists).
          */
         mutex_lock(&of->mutex);
         if (!kernfs_get_active(of->kn)) {
@@ -299,19 +300,27 @@ static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
                 goto out_free;
         }
 
+        if (copy_from_user(buf, user_buf, len)) {
+                len = -EFAULT;
+                goto out_unlock;
+        }
+        buf[len] = '\0';        /* guarantee string termination */
+
         ops = kernfs_ops(of->kn);
         if (ops->write)
                 len = ops->write(of, buf, len, *ppos);
         else
                 len = -EINVAL;
 
-        kernfs_put_active(of->kn);
-        mutex_unlock(&of->mutex);
-
         if (len > 0)
                 *ppos += len;
+
+out_unlock:
+        kernfs_put_active(of->kn);
+        mutex_unlock(&of->mutex);
 out_free:
-        kfree(buf);
+        if (buf != of->prealloc_buf)
+                kfree(buf);
         return len;
 }
 
@@ -685,6 +694,22 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
          */
         of->atomic_write_len = ops->atomic_write_len;
 
+        error = -EINVAL;
+        /*
+         * ->seq_show is incompatible with ->prealloc,
+         * as seq_read does its own allocation.
+         * ->read must be used instead.
+         */
+        if (ops->prealloc && ops->seq_show)
+                goto err_free;
+        if (ops->prealloc) {
+                int len = of->atomic_write_len ?: PAGE_SIZE;
+                of->prealloc_buf = kmalloc(len + 1, GFP_KERNEL);
+                error = -ENOMEM;
+                if (!of->prealloc_buf)
+                        goto err_free;
+        }
+
         /*
          * Always instantiate seq_file even if read access doesn't use
          * seq_file or is not requested.  This unifies private data access
@@ -715,6 +740,7 @@ static int kernfs_fop_open(struct inode *inode, struct file *file)
 err_close:
         seq_release(inode, file);
 err_free:
+        kfree(of->prealloc_buf);
         kfree(of);
 err_out:
         kernfs_put_active(kn);
@@ -728,6 +754,7 @@ static int kernfs_fop_release(struct inode *inode, struct file *filp)
 
         kernfs_put_open_node(kn, of);
         seq_release(inode, filp);
+        kfree(of->prealloc_buf);
         kfree(of);
 
         return 0;