Btrfs: add better -ENOSPC handling

This is a step in the direction of better -ENOSPC handling.  Instead of
checking the global bytes counter we check the space_info bytes counters to
make sure we have enough space.

If we don't we go ahead and try to allocate a new chunk, and then if that fails
we return -ENOSPC.  This patch adds two counters to btrfs_space_info,
bytes_delalloc and bytes_may_use.

bytes_delalloc account for extents we've actually setup for delalloc and will
be allocated at some point down the line. 

bytes_may_use is to keep track of how many bytes we may use for delalloc at
some point.  When we actually set the extent_bit for the delalloc bytes we
subtract the reserved bytes from the bytes_may_use counter.  This keeps us from
not actually being able to allocate space for any delalloc bytes.

Signed-off-by: Josef Bacik <jbacik@redhat.com>

1 files changed, 13 insertions, 3 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 872f104576e5..dc78954861b3 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1091,19 +1091,24 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
                 WARN_ON(num_pages > nrptrs);
                 memset(pages, 0, sizeof(struct page *) * nrptrs);
 
-                ret = btrfs_check_free_space(root, write_bytes, 0);
+                ret = btrfs_check_data_free_space(root, inode, write_bytes);
                 if (ret)
                         goto out;
 
                 ret = prepare_pages(root, file, pages, num_pages,
                                     pos, first_index, last_index,
                                     write_bytes);
-                if (ret)
+                if (ret) {
+                        btrfs_free_reserved_data_space(root, inode,
+                                                       write_bytes);
                         goto out;
+                }
 
                 ret = btrfs_copy_from_user(pos, num_pages,
                                            write_bytes, pages, buf);
                 if (ret) {
+                        btrfs_free_reserved_data_space(root, inode,
+                                                       write_bytes);
                         btrfs_drop_pages(pages, num_pages);
                         goto out;
                 }
@@ -1111,8 +1116,11 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
                 ret = dirty_and_release_pages(NULL, root, file, pages,
                                               num_pages, pos, write_bytes);
                 btrfs_drop_pages(pages, num_pages);
-                if (ret)
+                if (ret) {
+                        btrfs_free_reserved_data_space(root, inode,
+                                                       write_bytes);
                         goto out;
+                }
 
                 if (will_write) {
                         btrfs_fdatawrite_range(inode->i_mapping, pos,
@@ -1136,6 +1144,8 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
         }
 out:
         mutex_unlock(&inode->i_mutex);
+        if (ret)
+                err = ret;
 
 out_nolock:
         kfree(pages);