Btrfs: Implement basic support for -ENOSPC

This is intended to prevent accidentally filling the drive.  A determined
user can still make things oops.

It includes some accounting of the current bytes under delayed allocation,
but this will change as things get optimized

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 24 insertions, 4 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 461b09663fed..71dc2d33b6c6 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -307,6 +307,7 @@ static int dirty_and_release_pages(struct btrfs_trans_handle *trans,
             inline_size > 32768 ||
             inline_size >= BTRFS_MAX_INLINE_DATA_SIZE(root)) {
                 u64 last_end;
+                u64 existing_delalloc = 0;
 
                 for (i = 0; i < num_pages; i++) {
                         struct page *p = pages[i];
@@ -316,8 +317,19 @@ static int dirty_and_release_pages(struct btrfs_trans_handle *trans,
                 last_end = (u64)(pages[num_pages -1]->index) <<
                                 PAGE_CACHE_SHIFT;
                 last_end += PAGE_CACHE_SIZE - 1;
+                if (start_pos < isize) {
+                        u64 delalloc_start = start_pos;
+                        existing_delalloc = count_range_bits(em_tree,
+                                             &delalloc_start,
+                                             end_of_last_block, (u64)-1,
+                                             EXTENT_DELALLOC);
+                }
                 set_extent_delalloc(em_tree, start_pos, end_of_last_block,
                                  GFP_NOFS);
+                spin_lock(&root->fs_info->delalloc_lock);
+                root->fs_info->delalloc_bytes += (end_of_last_block + 1 -
+                                          start_pos) - existing_delalloc;
+                spin_unlock(&root->fs_info->delalloc_lock);
         } else {
                 u64 aligned_end;
                 /* step one, delete the existing extents in this range */
@@ -708,12 +720,12 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
         current->backing_dev_info = inode->i_mapping->backing_dev_info;
         err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
         if (err)
-                goto out;
+                goto out_nolock;
         if (count == 0)
-                goto out;
+                goto out_nolock;
         err = remove_suid(fdentry(file));
         if (err)
-                goto out;
+                goto out_nolock;
         file_update_time(file);
 
         pages = kmalloc(nrptrs * sizeof(struct page *), GFP_KERNEL);
@@ -758,6 +770,13 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
 
                 WARN_ON(num_pages > nrptrs);
                 memset(pages, 0, sizeof(pages));
+
+                mutex_lock(&root->fs_info->fs_mutex);
+                ret = btrfs_check_free_space(root, write_bytes, 0);
+                mutex_unlock(&root->fs_info->fs_mutex);
+                if (ret)
+                        goto out;
+
                 ret = prepare_pages(root, file, pages, num_pages,
                                     pos, first_index, last_index,
                                     write_bytes);
@@ -787,8 +806,9 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
                         btrfs_btree_balance_dirty(root, 1);
                 cond_resched();
         }
-        mutex_unlock(&inode->i_mutex);
 out:
+        mutex_unlock(&inode->i_mutex);
+out_nolock:
         kfree(pages);
         if (pinned[0])
                 page_cache_release(pinned[0]);