hfsplus: prevent btree data loss on ENOSPC

Inserting or deleting a record in a btree may require splitting several of
its nodes.  If we hit ENOSPC halfway through, the new nodes will be left
orphaned and their records will be lost.  This could mean lost inodes,
extents or xattrs.

Henceforth, check the available disk space before making any changes.
This still leaves the potential problem of corruption on ENOMEM.

The patch can be tested with xfstests generic/027.

Link: http://lkml.kernel.org/r/4596eef22fbda137b4ffa0272d92f0da15364421.1536269129.git.ernesto.mnd.fernandez@gmail.com
Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/hfsplus/extents.c b/fs/hfsplus/extents.c
index 8e0f59767694..8a8893d522ef 100644
--- a/fs/hfsplus/extents.c
+++ b/fs/hfsplus/extents.c
@@ -100,6 +100,10 @@ static int __hfsplus_ext_write_extent(struct inode *inode,
         if (hip->extent_state & HFSPLUS_EXT_NEW) {
                 if (res != -ENOENT)
                         return res;
+                /* Fail early and avoid ENOSPC during the btree operation */
+                res = hfs_bmap_reserve(fd->tree, fd->tree->depth + 1);
+                if (res)
+                        return res;
                 hfs_brec_insert(fd, hip->cached_extents,
                                 sizeof(hfsplus_extent_rec));
                 hip->extent_state &= ~(HFSPLUS_EXT_DIRTY | HFSPLUS_EXT_NEW);