ext4: prevent partial update of the extent blocks

BugLink: https://bugs.launchpad.net/bugs/1967582
commit 0f2f87d51aebcf71a709b52f661d681594c7dffa upstream.

In the most error path of current extents updating operations are not
roll back partial updates properly when some bad things happens(.e.g in
ext4_ext_insert_extent()). So we may get an inconsistent extents tree
if journal has been aborted due to IO error, which may probability lead
to BUGON later when we accessing these extent entries in errors=continue
mode. This patch drop extent buffer's verify flag before updatng the
contents in ext4_ext_get_access(), and reset it after updating in
__ext4_ext_dirty(). After this patch we could force to check the extent
buffer if extents tree updating was break off, make sure the extents are
consistent.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20210908120850.4012324-4-yi.zhang@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Leah Rumancik <leah.rumancik@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index c96495edff422daca01c43c9e0ce8b5ddad9b80f..9bcfdc864a3a0d387e596141c9d407354be4d1f4 100644 (file)
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -133,14 +133,25 @@ static int ext4_ext_truncate_extend_restart(handle_t *handle,
 static int ext4_ext_get_access(handle_t *handle, struct inode *inode,
                                struct ext4_ext_path *path)
 {
+       int err = 0;
+
        if (path->p_bh) {
                /* path points to block */
                BUFFER_TRACE(path->p_bh, "get_write_access");
-               return ext4_journal_get_write_access(handle, path->p_bh);
+               err = ext4_journal_get_write_access(handle, path->p_bh);
+
+               /*
+                * The extent buffer's verified bit will be set again in
+                * __ext4_ext_dirty(). We could leave an inconsistent
+                * buffer if the extents updating procudure break off du
+                * to some error happens, force to check it again.
+                */
+               if (!err)
+                       clear_buffer_verified(path->p_bh);
        }
        /* path points to leaf/index in inode body */
        /* we use in-core data, no need to protect them */
-       return 0;
+       return err;
 }
 
 /*
@@ -160,6 +171,9 @@ int __ext4_ext_dirty(const char *where, unsigned int line, handle_t *handle,
                /* path points to block */
                err = __ext4_handle_dirty_metadata(where, line, handle,
                                                   inode, path->p_bh);
+               /* Extents updating done, re-set verified flag */
+               if (!err)
+                       set_buffer_verified(path->p_bh);
        } else {
                /* path points to leaf/index in inode body */
                err = ext4_mark_inode_dirty(handle, inode);