Merge git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable

* git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable: (27 commits)
  Btrfs: add more error checking to btrfs_dirty_inode
  Btrfs: allow unaligned DIO
  Btrfs: drop verbose enospc printk
  Btrfs: Fix block generation verification race
  Btrfs: fix preallocation and nodatacow checks in O_DIRECT
  Btrfs: avoid ENOSPC errors in btrfs_dirty_inode
  Btrfs: move O_DIRECT space reservation to btrfs_direct_IO
  Btrfs: rework O_DIRECT enospc handling
  Btrfs: use async helpers for DIO write checksumming
  Btrfs: don't walk around with task->state != TASK_RUNNING
  Btrfs: do aio_write instead of write
  Btrfs: add basic DIO read/write support
  direct-io: do not merge logically non-contiguous requests
  direct-io: add a hook for the fs to provide its own submit_bio function
  fs: allow short direct-io reads to be completed via buffered IO
  Btrfs: Metadata ENOSPC handling for balance
  Btrfs: Pre-allocate space for data relocation
  Btrfs: Metadata ENOSPC handling for tree log
  Btrfs: Metadata reservation for orphan inodes
  Btrfs: Introduce global metadata reservation
  ...

1 files changed, 31 insertions, 5 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 35e12d186566..45a2d18df849 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1275,7 +1275,7 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
 {
         struct file *filp = iocb->ki_filp;
         ssize_t retval;
-        unsigned long seg;
+        unsigned long seg = 0;
         size_t count;
         loff_t *ppos = &iocb->ki_pos;
 
@@ -1302,21 +1302,47 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
                                 retval = mapping->a_ops->direct_IO(READ, iocb,
                                                         iov, pos, nr_segs);
                         }
-                        if (retval > 0)
+                        if (retval > 0) {
                                 *ppos = pos + retval;
-                        if (retval) {
+                                count -= retval;
+                        }
+
+                        /*
+                         * Btrfs can have a short DIO read if we encounter
+                         * compressed extents, so if there was an error, or if
+                         * we've already read everything we wanted to, or if
+                         * there was a short read because we hit EOF, go ahead
+                         * and return.  Otherwise fallthrough to buffered io for
+                         * the rest of the read.
+                         */
+                        if (retval < 0 || !count || *ppos >= size) {
                                 file_accessed(filp);
                                 goto out;
                         }
                 }
         }
 
+        count = retval;
         for (seg = 0; seg < nr_segs; seg++) {
                 read_descriptor_t desc;
+                loff_t offset = 0;
+
+                /*
+                 * If we did a short DIO read we need to skip the section of the
+                 * iov that we've already read data into.
+                 */
+                if (count) {
+                        if (count > iov[seg].iov_len) {
+                                count -= iov[seg].iov_len;
+                                continue;
+                        }
+                        offset = count;
+                        count = 0;
+                }
 
                 desc.written = 0;
-                desc.arg.buf = iov[seg].iov_base;
-                desc.count = iov[seg].iov_len;
+                desc.arg.buf = iov[seg].iov_base + offset;
+                desc.count = iov[seg].iov_len - offset;
                 if (desc.count == 0)
                         continue;
                 desc.error = 0;