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Commit 96d2a495 authored by Eric Sandeen's avatar Eric Sandeen Committed by Jan Kara
Browse files

ext3: Replace lock/unlock_super() with an explicit lock for resizing 



Use a separate lock to protect s_groups_count and the other block
group descriptors which get changed via an on-line resize operation,
so we can stop overloading the use of lock_super().

Port of ext4 commit 32ed5058 by
Theodore Ts'o <tytso@mit.edu>.

CC: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: default avatarEric Sandeen <sandeen@redhat.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent b8a052d0

fs/ext3/resize.c

+18 −17
Original line number Diff line number Diff line
@@ -209,7 +209,7 @@ static int setup_new_group_blocks(struct super_block *sb, 
	if (IS_ERR(handle))

		return PTR_ERR(handle);



	lock_super(sb);

	mutex_lock(&sbi->s_resize_lock);

	if (input->group != sbi->s_groups_count) {

		err = -EBUSY;

		goto exit_journal;
@@ -324,7 +324,7 @@ static int setup_new_group_blocks(struct super_block *sb, 
	brelse(bh);



exit_journal:

	unlock_super(sb);

	mutex_unlock(&sbi->s_resize_lock);

	if ((err2 = ext3_journal_stop(handle)) && !err)

		err = err2;
@@ -662,11 +662,12 @@ static int reserve_backup_gdb(handle_t *handle, struct inode *inode, 
 * important part is that the new block and inode counts are in the backup

 * superblocks, and the location of the new group metadata in the GDT backups.

 *

 * We do not need lock_super() for this, because these blocks are not

 * otherwise touched by the filesystem code when it is mounted.  We don't

 * need to worry about last changing from sbi->s_groups_count, because the

 * worst that can happen is that we do not copy the full number of backups

 * at this time.  The resize which changed s_groups_count will backup again.

 * We do not need take the s_resize_lock for this, because these

 * blocks are not otherwise touched by the filesystem code when it is

 * mounted.  We don't need to worry about last changing from

 * sbi->s_groups_count, because the worst that can happen is that we

 * do not copy the full number of backups at this time.  The resize

 * which changed s_groups_count will backup again.

 */

static void update_backups(struct super_block *sb,

			   int blk_off, char *data, int size)
@@ -825,7 +826,7 @@ int ext3_group_add(struct super_block *sb, struct ext3_new_group_data *input) 
		goto exit_put;

	}



	lock_super(sb);

	mutex_lock(&sbi->s_resize_lock);

	if (input->group != sbi->s_groups_count) {

		ext3_warning(sb, __func__,

			     "multiple resizers run on filesystem!");
@@ -856,7 +857,7 @@ int ext3_group_add(struct super_block *sb, struct ext3_new_group_data *input) 
	/*

	 * OK, now we've set up the new group.  Time to make it active.

	 *

	 * Current kernels don't lock all allocations via lock_super(),

	 * We do not lock all allocations via s_resize_lock

	 * so we have to be safe wrt. concurrent accesses the group

	 * data.  So we need to be careful to set all of the relevant

	 * group descriptor data etc. *before* we enable the group.
@@ -900,12 +901,12 @@ int ext3_group_add(struct super_block *sb, struct ext3_new_group_data *input) 
	 *

	 * The precise rules we use are:

	 *

	 * * Writers of s_groups_count *must* hold lock_super

	 * * Writers of s_groups_count *must* hold s_resize_lock

	 * AND

	 * * Writers must perform a smp_wmb() after updating all dependent

	 *   data and before modifying the groups count

	 *

	 * * Readers must hold lock_super() over the access

	 * * Readers must hold s_resize_lock over the access

	 * OR

	 * * Readers must perform an smp_rmb() after reading the groups count

	 *   and before reading any dependent data.
@@ -936,7 +937,7 @@ int ext3_group_add(struct super_block *sb, struct ext3_new_group_data *input) 
	ext3_journal_dirty_metadata(handle, sbi->s_sbh);



exit_journal:

	unlock_super(sb);

	mutex_unlock(&sbi->s_resize_lock);

	if ((err2 = ext3_journal_stop(handle)) && !err)

		err = err2;

	if (!err) {
@@ -973,7 +974,7 @@ int ext3_group_extend(struct super_block *sb, struct ext3_super_block *es, 


	/* We don't need to worry about locking wrt other resizers just

	 * yet: we're going to revalidate es->s_blocks_count after

	 * taking lock_super() below. */

	 * taking the s_resize_lock below. */

	o_blocks_count = le32_to_cpu(es->s_blocks_count);

	o_groups_count = EXT3_SB(sb)->s_groups_count;
@@ -1045,11 +1046,11 @@ int ext3_group_extend(struct super_block *sb, struct ext3_super_block *es, 
		goto exit_put;

	}



	lock_super(sb);

	mutex_lock(&EXT3_SB(sb)->s_resize_lock);

	if (o_blocks_count != le32_to_cpu(es->s_blocks_count)) {

		ext3_warning(sb, __func__,

			     "multiple resizers run on filesystem!");

		unlock_super(sb);

		mutex_unlock(&EXT3_SB(sb)->s_resize_lock);

		ext3_journal_stop(handle);

		err = -EBUSY;

		goto exit_put;
@@ -1059,13 +1060,13 @@ int ext3_group_extend(struct super_block *sb, struct ext3_super_block *es, 
						 EXT3_SB(sb)->s_sbh))) {

		ext3_warning(sb, __func__,

			     "error %d on journal write access", err);

		unlock_super(sb);

		mutex_unlock(&EXT3_SB(sb)->s_resize_lock);

		ext3_journal_stop(handle);

		goto exit_put;

	}

	es->s_blocks_count = cpu_to_le32(o_blocks_count + add);

	ext3_journal_dirty_metadata(handle, EXT3_SB(sb)->s_sbh);

	unlock_super(sb);

	mutex_unlock(&EXT3_SB(sb)->s_resize_lock);

	ext3_debug("freeing blocks %lu through "E3FSBLK"\n", o_blocks_count,

		   o_blocks_count + add);

	ext3_free_blocks_sb(handle, sb, o_blocks_count, add, &freed_blocks);

fs/ext3/super.c

+1 −0
Original line number Diff line number Diff line
@@ -1929,6 +1929,7 @@ static int ext3_fill_super (struct super_block *sb, void *data, int silent) 
#endif

	INIT_LIST_HEAD(&sbi->s_orphan); /* unlinked but open files */

	mutex_init(&sbi->s_orphan_lock);

	mutex_init(&sbi->s_resize_lock);



	sb->s_root = NULL;

include/linux/ext3_fs_sb.h

+1 −0
Original line number Diff line number Diff line
@@ -73,6 +73,7 @@ struct ext3_sb_info { 
	struct journal_s * s_journal;

	struct list_head s_orphan;

	struct mutex s_orphan_lock;

	struct mutex s_resize_lock;

	unsigned long s_commit_interval;

	struct block_device *journal_bdev;

#ifdef CONFIG_JBD_DEBUG