udf: Fix deadlock when converting file from in-ICB one to normal one

During BKL removal in 2.6.38, conversion of files from in-ICB format to normal
format got broken. We call ->writepage with i_data_sem held but udf_get_block()
also acquires i_data_sem thus creating A-A deadlock.

We fix the problem by dropping i_data_sem before calling ->writepage() which is
safe since i_mutex still protects us against any changes in the file. Also fix
pagelock - i_data_sem lock inversion in udf_expand_file_adinicb() by dropping
i_data_sem before calling find_or_create_page().

CC: stable@kernel.org
Reported-by: Matthias Matiak <netzpython@mail-on.us>
Tested-by: Matthias Matiak <netzpython@mail-on.us>
Reviewed-by: Namjae Jeon <linkinjeon@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/udf/file.c b/fs/udf/file.c
index d8ffa7c..dca0c38 100644 (file)
--- a/fs/udf/file.c
+++ b/fs/udf/file.c
@@ -125,7 +125,6 @@ static ssize_t udf_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
                        err = udf_expand_file_adinicb(inode);
                        if (err) {
                                udf_debug("udf_expand_adinicb: err=%d\n", err);
-                               up_write(&iinfo->i_data_sem);
                                return err;
                        }
                } else {
@@ -133,9 +132,10 @@ static ssize_t udf_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
                                iinfo->i_lenAlloc = pos + count;
                        else
                                iinfo->i_lenAlloc = inode->i_size;
+                       up_write(&iinfo->i_data_sem);
                }
-       }
-       up_write(&iinfo->i_data_sem);
+       } else
+               up_write(&iinfo->i_data_sem);
 
        retval = generic_file_aio_write(iocb, iov, nr_segs, ppos);
        if (retval > 0)

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 1bd2c42..4f7b1ff 100644 (file)
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -150,6 +150,12 @@ const struct address_space_operations udf_aops = {
        .bmap           = udf_bmap,
 };
 
+/*
+ * Expand file stored in ICB to a normal one-block-file
+ *
+ * This function requires i_data_sem for writing and releases it.
+ * This function requires i_mutex held
+ */
 int udf_expand_file_adinicb(struct inode *inode)
 {
        struct page *page;
@@ -168,9 +174,15 @@ int udf_expand_file_adinicb(struct inode *inode)
                        iinfo->i_alloc_type = ICBTAG_FLAG_AD_LONG;
                /* from now on we have normal address_space methods */
                inode->i_data.a_ops = &udf_aops;
+               up_write(&iinfo->i_data_sem);
                mark_inode_dirty(inode);
                return 0;
        }
+       /*
+        * Release i_data_sem so that we can lock a page - page lock ranks
+        * above i_data_sem. i_mutex still protects us against file changes.
+        */
+       up_write(&iinfo->i_data_sem);
 
        page = find_or_create_page(inode->i_mapping, 0, GFP_NOFS);
        if (!page)
@@ -186,6 +198,7 @@ int udf_expand_file_adinicb(struct inode *inode)
                SetPageUptodate(page);
                kunmap(page);
        }
+       down_write(&iinfo->i_data_sem);
        memset(iinfo->i_ext.i_data + iinfo->i_lenEAttr, 0x00,
               iinfo->i_lenAlloc);
        iinfo->i_lenAlloc = 0;
@@ -195,17 +208,20 @@ int udf_expand_file_adinicb(struct inode *inode)
                iinfo->i_alloc_type = ICBTAG_FLAG_AD_LONG;
        /* from now on we have normal address_space methods */
        inode->i_data.a_ops = &udf_aops;
+       up_write(&iinfo->i_data_sem);
        err = inode->i_data.a_ops->writepage(page, &udf_wbc);
        if (err) {
                /* Restore everything back so that we don't lose data... */
                lock_page(page);
                kaddr = kmap(page);
+               down_write(&iinfo->i_data_sem);
                memcpy(iinfo->i_ext.i_data + iinfo->i_lenEAttr, kaddr,
                       inode->i_size);
                kunmap(page);
                unlock_page(page);
                iinfo->i_alloc_type = ICBTAG_FLAG_AD_IN_ICB;
                inode->i_data.a_ops = &udf_adinicb_aops;
+               up_write(&iinfo->i_data_sem);
        }
        page_cache_release(page);
        mark_inode_dirty(inode);
@@ -1105,10 +1121,9 @@ int udf_setsize(struct inode *inode, loff_t newsize)
                        if (bsize <
                            (udf_file_entry_alloc_offset(inode) + newsize)) {
                                err = udf_expand_file_adinicb(inode);
-                               if (err) {
-                                       up_write(&iinfo->i_data_sem);
+                               if (err)
                                        return err;
-                               }
+                               down_write(&iinfo->i_data_sem);
                        } else
                                iinfo->i_lenAlloc = newsize;
                }