ext4: fix BUG when calling ext4_error with locked block group

The mballoc code likes to call ext4_error while it is holding locked
block groups.  This can causes a scheduling in atomic context BUG.  We
can't just unlock the block group and relock it after/if ext4_error
returns since that might result in race conditions in the case where
the filesystem is set to continue after finding errors.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 43 insertions, 2 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index a9dd117..2415e2b 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -366,6 +366,44 @@ void ext4_warning(struct super_block *sb, const char *function,
 	va_end(args);
 }
 
+void ext4_grp_locked_error(struct super_block *sb, ext4_group_t grp,
+				const char *function, const char *fmt, ...)
+__releases(bitlock)
+__acquires(bitlock)
+{
+	va_list args;
+	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
+
+	va_start(args, fmt);
+	printk(KERN_CRIT "EXT4-fs error (device %s): %s: ", sb->s_id, function);
+	vprintk(fmt, args);
+	printk("\n");
+	va_end(args);
+
+	if (test_opt(sb, ERRORS_CONT)) {
+		EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
+		es->s_state |= cpu_to_le16(EXT4_ERROR_FS);
+		ext4_commit_super(sb, es, 0);
+		return;
+	}
+	ext4_unlock_group(sb, grp);
+	ext4_handle_error(sb);
+	/*
+	 * We only get here in the ERRORS_RO case; relocking the group
+	 * may be dangerous, but nothing bad will happen since the
+	 * filesystem will have already been marked read/only and the
+	 * journal has been aborted.  We return 1 as a hint to callers
+	 * who might what to use the return value from
+	 * ext4_grp_locked_error() to distinguish beween the
+	 * ERRORS_CONT and ERRORS_RO case, and perhaps return more
+	 * aggressively from the ext4 function in question, with a
+	 * more appropriate error code.
+	 */
+	ext4_lock_group(sb, grp);
+	return;
+}
+
+
 void ext4_update_dynamic_rev(struct super_block *sb)
 {
 	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
@@ -2868,8 +2906,11 @@ static void ext4_commit_super(struct super_block *sb,
 		set_buffer_uptodate(sbh);
 	}
 	es->s_wtime = cpu_to_le32(get_seconds());
-	ext4_free_blocks_count_set(es, ext4_count_free_blocks(sb));
-	es->s_free_inodes_count = cpu_to_le32(ext4_count_free_inodes(sb));
+	ext4_free_blocks_count_set(es, percpu_counter_sum_positive(
+					&EXT4_SB(sb)->s_freeblocks_counter));
+	es->s_free_inodes_count = cpu_to_le32(percpu_counter_sum_positive(
+					&EXT4_SB(sb)->s_freeinodes_counter));
+
 	BUFFER_TRACE(sbh, "marking dirty");
 	mark_buffer_dirty(sbh);
 	if (sync) {