[PATCH v3] ext4: initialize multi-block allocator before checking block descriptors

[Azat Khuzhin <a3at.mail@gmail.com>]

With EXT4FS_DEBUG ext4_count_free_clusters() will call
ext4_read_block_bitmap() without s_group_info initialized, so we need to
initialize multi-block allocator before.

And we can't initialize multi-block allocator without group descriptors,
since it use them.
Also we need to install s_op before initializing multi-block allocator,
because in ext4_mb_init_backend() new inode is created.

Here is bt:
(gdb) bt
 #0  ext4_get_group_info (group=0, sb=0xffff880079a10000) at ext4.h:2430
 #1  ext4_validate_block_bitmap (sb=sb@entry=0xffff880079a10000, desc=desc@entry=0xffff880056510000, block_group=block_group@entry=0,
     bh=bh@entry=0xffff88007bf2b2d8) at balloc.c:358
 #2  0xffffffff81232202 in ext4_wait_block_bitmap (sb=sb@entry=0xffff880079a10000, block_group=block_group@entry=0,
     bh=bh@entry=0xffff88007bf2b2d8) at balloc.c:476
 #3  0xffffffff81232eaf in ext4_read_block_bitmap (sb=sb@entry=0xffff880079a10000, block_group=block_group@entry=0) at balloc.c:489
 #4  0xffffffff81232fc0 in ext4_count_free_clusters (sb=sb@entry=0xffff880079a10000) at balloc.c:665
 #5  0xffffffff81259ffa in ext4_check_descriptors (first_not_zeroed=<synthetic pointer>, sb=0xffff880079a10000) at super.c:2143
 #6  ext4_fill_super (sb=sb@entry=0xffff880079a10000, data=<optimized out>, data@entry=0x0 <irq_stack_union>, silent=silent@entry=0)
     at super.c:3851
 #7  0xffffffff811b8340 in mount_bdev (fs_type=<optimized out>, flags=0, dev_name=<optimized out>, data=0x0 <irq_stack_union>,
     fill_super=fill_super@entry=0xffffffff812589c0 <ext4_fill_super>) at super.c:987
 #8  0xffffffff8124ec35 in ext4_mount (fs_type=<optimized out>, flags=<optimized out>, dev_name=<optimized out>, data=<optimized out>)
     at super.c:5365
 #9  0xffffffff811b8cf9 in mount_fs (type=type@entry=0xffffffff81c71840 <ext4_fs_type>, flags=flags@entry=0,
     name=name@entry=0xffff880077a80c70 "/dev/loop4", data=data@entry=0x0 <irq_stack_union>) at super.c:1090
 #10 0xffffffff811d2ff3 in vfs_kern_mount (type=type@entry=0xffffffff81c71840 <ext4_fs_type>, flags=0,
     name=name@entry=0xffff880077a80c70 "/dev/loop4", data=data@entry=0x0 <irq_stack_union>) at namespace.c:813
 #11 0xffffffff811d55de in do_new_mount (data=0x0 <irq_stack_union>, name=0xffff880077a80c70 "/dev/loop4", mnt_flags=32,
     flags=<optimized out>, fstype=0xffff880077a80ca0 "ext4-insane", path=0xffff88007a5b1ed0) at namespace.c:2068
 #12 do_mount (dev_name=0xffff880077a80c70 "/dev/loop4", dir_name=<optimized out>, type_page=0xffff880077a80ca0 "ext4-insane",
     flags=<optimized out>, flags@entry=3236757504, data_page=0x0 <irq_stack_union>) at namespace.c:2392
 #13 0xffffffff811d6183 in SYSC_mount (data=0x0 <irq_stack_union>, flags=3236757504, type=<optimized out>, dir_name=<optimized out>,
     dev_name=0x7ffad9649c20 "/dev/loop4") at namespace.c:2586
 #14 SyS_mount (dev_name=140715365800992, dir_name=<optimized out>, type=<optimized out>, flags=3236757504, data=0) at namespace.c:2559

Signed-off-by: Azat Khuzhin <a3at.mail@gmail.com>
---
v2: ext4: initialize multi-block allocator after group descriptors loaded
v3: ext4: set s_op before initializing multi-block allocator

 fs/ext4/super.c | 44 +++++++++++++++++++++++---------------------
 1 file changed, 23 insertions(+), 21 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 1f7784d..fc42ee0 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3848,16 +3848,34 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 			goto failed_mount2;
 		}
 	}
+
+	/*
+	 * set up enough so that it can read an inode
+	 */
+	if (!test_opt(sb, NOLOAD) &&
+	    EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL))
+		sb->s_op = &ext4_sops;
+	else
+		sb->s_op = &ext4_nojournal_sops;
+
+	ext4_ext_init(sb);
+	err = ext4_mb_init(sb);
+	if (err) {
+		ext4_msg(sb, KERN_ERR, "failed to initialize mballoc (%d)",
+			 err);
+		goto failed_mount2;
+	}
+
 	if (!ext4_check_descriptors(sb, &first_not_zeroed)) {
 		ext4_msg(sb, KERN_ERR, "group descriptors corrupted!");
-		goto failed_mount2;
+		goto failed_mount2a;
 	}
 	if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
 		if (!ext4_fill_flex_info(sb)) {
 			ext4_msg(sb, KERN_ERR,
 			       "unable to initialize "
 			       "flex_bg meta info!");
-			goto failed_mount2;
+			goto failed_mount2a;
 		}
 
 	sbi->s_gdb_count = db_count;
@@ -3895,14 +3913,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	sbi->s_stripe = ext4_get_stripe_size(sbi);
 	sbi->s_extent_max_zeroout_kb = 32;
 
-	/*
-	 * set up enough so that it can read an inode
-	 */
-	if (!test_opt(sb, NOLOAD) &&
-	    EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL))
-		sb->s_op = &ext4_sops;
-	else
-		sb->s_op = &ext4_nojournal_sops;
 	sb->s_export_op = &ext4_export_ops;
 	sb->s_xattr = ext4_xattr_handlers;
 #ifdef CONFIG_QUOTA
@@ -4094,14 +4104,6 @@ no_journal:
 		goto failed_mount4a;
 	}
 
-	ext4_ext_init(sb);
-	err = ext4_mb_init(sb);
-	if (err) {
-		ext4_msg(sb, KERN_ERR, "failed to initialize mballoc (%d)",
-			 err);
-		goto failed_mount5;
-	}
-
 	err = ext4_register_li_request(sb, first_not_zeroed);
 	if (err)
 		goto failed_mount6;
@@ -4175,9 +4177,6 @@ failed_mount8:
 failed_mount7:
 	ext4_unregister_li_request(sb);
 failed_mount6:
-	ext4_mb_release(sb);
-failed_mount5:
-	ext4_ext_release(sb);
 	ext4_release_system_zone(sb);
 failed_mount4a:
 	dput(sb->s_root);
@@ -4203,11 +4202,14 @@ failed_mount3:
 	percpu_counter_destroy(&sbi->s_extent_cache_cnt);
 	if (sbi->s_mmp_tsk)
 		kthread_stop(sbi->s_mmp_tsk);
+failed_mount2a:
+	ext4_mb_release(sb);
 failed_mount2:
 	for (i = 0; i < db_count; i++)
 		brelse(sbi->s_group_desc[i]);
 	ext4_kvfree(sbi->s_group_desc);
 failed_mount:
+	ext4_ext_release(sb);
 	if (sbi->s_chksum_driver)
 		crypto_free_shash(sbi->s_chksum_driver);
 	if (sbi->s_proc) {
-- 
1.8.5.3