Add a per-inode lock around btrfs_drop_extents

btrfs_drop_extents is always called with a range lock held on the inode.
But, it may operate on extents outside that range as it drops and splits
them.

This patch adds a per-inode mutex that is held while calling
btrfs_drop_extents and while inserting new extents into the tree.  It
prevents races from two procs working against adjacent ranges in the tree.

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

1 files changed, 8 insertions, 0 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 3e4e5c227c0c..40ad1b2958cb 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -242,6 +242,7 @@ static int noinline dirty_and_release_pages(struct btrfs_trans_handle *trans,
         u64 end_of_last_block;
         u64 end_pos = pos + write_bytes;
         u64 inline_size;
+        int did_inline = 0;
         loff_t isize = i_size_read(inode);
 
         start_pos = pos & ~((u64)root->sectorsize - 1);
@@ -275,6 +276,7 @@ static int noinline dirty_and_release_pages(struct btrfs_trans_handle *trans,
                 if (hole_size > 0) {
                         btrfs_wait_ordered_range(inode, last_pos_in_file,
                                                  last_pos_in_file + hole_size);
+                        mutex_lock(&BTRFS_I(inode)->extent_mutex);
                         err = btrfs_drop_extents(trans, root, inode,
                                                  last_pos_in_file,
                                                  last_pos_in_file + hole_size,
@@ -289,6 +291,7 @@ static int noinline dirty_and_release_pages(struct btrfs_trans_handle *trans,
                                                        0, 0, hole_size, 0);
                         btrfs_drop_extent_cache(inode, last_pos_in_file,
                                         last_pos_in_file + hole_size -1);
+                        mutex_unlock(&BTRFS_I(inode)->extent_mutex);
                         btrfs_check_file(root, inode);
                 }
                 if (err)
@@ -321,6 +324,7 @@ static int noinline dirty_and_release_pages(struct btrfs_trans_handle *trans,
                 /* step one, delete the existing extents in this range */
                 aligned_end = (pos + write_bytes + root->sectorsize - 1) &
                         ~((u64)root->sectorsize - 1);
+                mutex_lock(&BTRFS_I(inode)->extent_mutex);
                 err = btrfs_drop_extents(trans, root, inode, start_pos,
                                          aligned_end, aligned_end, &hint_byte);
                 if (err)
@@ -332,9 +336,13 @@ static int noinline dirty_and_release_pages(struct btrfs_trans_handle *trans,
                                            inline_size, pages, 0, num_pages);
                 btrfs_drop_extent_cache(inode, start_pos, aligned_end - 1);
                 BUG_ON(err);
+                mutex_unlock(&BTRFS_I(inode)->extent_mutex);
+                did_inline = 1;
         }
         if (end_pos > isize) {
                 i_size_write(inode, end_pos);
+                if (did_inline)
+                        BTRFS_I(inode)->disk_i_size = end_pos;
                 btrfs_update_inode(trans, root, inode);
         }
 failed: