udf: Fix race between write(2) and close(2)
Currently write(2) updating i_size and close(2) of the file can race in
such a way that udf_truncate_tail_extent() called from
udf_file_release() sees old i_size but already new extents added by the
running write call. This results in complaints like:
UDF-fs: warning (device vdb2): udf_truncate_tail_extent: Too long extent
after EOF in inode 877: i_size: 0 lbcount: 1073739776 extent 0+1073739776
UDF-fs: error (device vdb2): udf_truncate_tail_extent: Extent after EOF
in inode 877
Fix the problem by grabbing i_mutex in udf_file_release() to be sure
i_size is consistent with current state of extent list. Also avoid
truncating tail extent unnecessarily when the file is still open for
writing.
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/udf/file.c b/fs/udf/file.c
index 86c6743..bb15771 100644
--- a/fs/udf/file.c
+++ b/fs/udf/file.c
@@ -223,11 +223,18 @@
static int udf_release_file(struct inode *inode, struct file *filp)
{
- if (filp->f_mode & FMODE_WRITE) {
+ if (filp->f_mode & FMODE_WRITE &&
+ atomic_read(&inode->i_writecount) > 1) {
+ /*
+ * Grab i_mutex to avoid races with writes changing i_size
+ * while we are running.
+ */
+ mutex_lock(&inode->i_mutex);
down_write(&UDF_I(inode)->i_data_sem);
udf_discard_prealloc(inode);
udf_truncate_tail_extent(inode);
up_write(&UDF_I(inode)->i_data_sem);
+ mutex_unlock(&inode->i_mutex);
}
return 0;
}