ext4: add debugging trigger for ext4_error()

Make it easy to test whether or not the error handling subsystem in
ext4 is working correctly.  This allows us to simulate an ext4_error()
by echoing a string to /sys/fs/ext4/<dev>/trigger_fs_error.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: ksumrall@google.com

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 511011a..decc15d 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1197,6 +1197,7 @@ struct ext4_sb_info {
        struct proc_dir_entry *s_proc;
        struct kobject s_kobj;
        struct completion s_kobj_unregister;
+       struct super_block *s_sb;
 
        /* Journaling */
        struct journal_s *s_journal;

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 628cfcd..9f1ae6b 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2473,6 +2473,23 @@ static ssize_t sbi_ui_store(struct ext4_attr *a,
        return count;
 }
 
+static ssize_t trigger_test_error(struct ext4_attr *a,
+                                 struct ext4_sb_info *sbi,
+                                 const char *buf, size_t count)
+{
+       int len = count;
+
+       if (!capable(CAP_SYS_ADMIN))
+               return -EPERM;
+
+       if (len && buf[len-1] == '\n')
+               len--;
+
+       if (len)
+               ext4_error(sbi->s_sb, "%.*s", len, buf);
+       return count;
+}
+
 #define EXT4_ATTR_OFFSET(_name,_mode,_show,_store,_elname) \
 static struct ext4_attr ext4_attr_##_name = {                  \
        .attr = {.name = __stringify(_name), .mode = _mode },   \
@@ -2503,6 +2520,7 @@ EXT4_RW_ATTR_SBI_UI(mb_order2_req, s_mb_order2_reqs);
 EXT4_RW_ATTR_SBI_UI(mb_stream_req, s_mb_stream_request);
 EXT4_RW_ATTR_SBI_UI(mb_group_prealloc, s_mb_group_prealloc);
 EXT4_RW_ATTR_SBI_UI(max_writeback_mb_bump, s_max_writeback_mb_bump);
+EXT4_ATTR(trigger_fs_error, 0200, NULL, trigger_test_error);
 
 static struct attribute *ext4_attrs[] = {
        ATTR_LIST(delayed_allocation_blocks),
@@ -2517,6 +2535,7 @@ static struct attribute *ext4_attrs[] = {
        ATTR_LIST(mb_stream_req),
        ATTR_LIST(mb_group_prealloc),
        ATTR_LIST(max_writeback_mb_bump),
+       ATTR_LIST(trigger_fs_error),
        NULL,
 };
 
@@ -3087,6 +3106,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
                goto out_free_orig;
        }
        sb->s_fs_info = sbi;
+       sbi->s_sb = sb;
        sbi->s_mount_opt = 0;
        sbi->s_resuid = EXT4_DEF_RESUID;
        sbi->s_resgid = EXT4_DEF_RESGID;