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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 32ed5058ce
by
Theodore Ts'o <tytso@mit.edu>.
CC: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
parent
b8a052d016
commit
96d2a495c2
3 changed files with 20 additions and 17 deletions
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@ -209,7 +209,7 @@ static int setup_new_group_blocks(struct super_block *sb,
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if (IS_ERR(handle))
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return PTR_ERR(handle);
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lock_super(sb);
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mutex_lock(&sbi->s_resize_lock);
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if (input->group != sbi->s_groups_count) {
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err = -EBUSY;
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goto exit_journal;
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@ -324,7 +324,7 @@ exit_bh:
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brelse(bh);
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exit_journal:
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unlock_super(sb);
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mutex_unlock(&sbi->s_resize_lock);
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if ((err2 = ext3_journal_stop(handle)) && !err)
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err = err2;
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@ -662,11 +662,12 @@ exit_free:
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* important part is that the new block and inode counts are in the backup
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* superblocks, and the location of the new group metadata in the GDT backups.
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*
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* We do not need lock_super() for this, because these blocks are not
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* otherwise touched by the filesystem code when it is mounted. We don't
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* need to worry about last changing from sbi->s_groups_count, because the
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* worst that can happen is that we do not copy the full number of backups
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* at this time. The resize which changed s_groups_count will backup again.
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* We do not need take the s_resize_lock for this, because these
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* blocks are not otherwise touched by the filesystem code when it is
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* mounted. We don't need to worry about last changing from
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* sbi->s_groups_count, because the worst that can happen is that we
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* do not copy the full number of backups at this time. The resize
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* which changed s_groups_count will backup again.
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*/
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static void update_backups(struct super_block *sb,
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int blk_off, char *data, int size)
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@ -825,7 +826,7 @@ int ext3_group_add(struct super_block *sb, struct ext3_new_group_data *input)
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goto exit_put;
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}
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lock_super(sb);
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mutex_lock(&sbi->s_resize_lock);
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if (input->group != sbi->s_groups_count) {
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ext3_warning(sb, __func__,
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"multiple resizers run on filesystem!");
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@ -856,7 +857,7 @@ int ext3_group_add(struct super_block *sb, struct ext3_new_group_data *input)
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/*
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* OK, now we've set up the new group. Time to make it active.
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*
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* Current kernels don't lock all allocations via lock_super(),
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* We do not lock all allocations via s_resize_lock
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* so we have to be safe wrt. concurrent accesses the group
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* data. So we need to be careful to set all of the relevant
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* group descriptor data etc. *before* we enable the group.
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@ -900,12 +901,12 @@ int ext3_group_add(struct super_block *sb, struct ext3_new_group_data *input)
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*
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* The precise rules we use are:
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*
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* * Writers of s_groups_count *must* hold lock_super
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* * Writers of s_groups_count *must* hold s_resize_lock
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* AND
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* * Writers must perform a smp_wmb() after updating all dependent
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* data and before modifying the groups count
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*
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* * Readers must hold lock_super() over the access
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* * Readers must hold s_resize_lock over the access
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* OR
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* * Readers must perform an smp_rmb() after reading the groups count
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* and before reading any dependent data.
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@ -936,7 +937,7 @@ int ext3_group_add(struct super_block *sb, struct ext3_new_group_data *input)
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ext3_journal_dirty_metadata(handle, sbi->s_sbh);
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exit_journal:
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unlock_super(sb);
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mutex_unlock(&sbi->s_resize_lock);
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if ((err2 = ext3_journal_stop(handle)) && !err)
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err = err2;
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if (!err) {
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@ -973,7 +974,7 @@ int ext3_group_extend(struct super_block *sb, struct ext3_super_block *es,
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/* We don't need to worry about locking wrt other resizers just
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* yet: we're going to revalidate es->s_blocks_count after
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* taking lock_super() below. */
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* taking the s_resize_lock below. */
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o_blocks_count = le32_to_cpu(es->s_blocks_count);
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o_groups_count = EXT3_SB(sb)->s_groups_count;
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@ -1045,11 +1046,11 @@ int ext3_group_extend(struct super_block *sb, struct ext3_super_block *es,
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goto exit_put;
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}
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lock_super(sb);
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mutex_lock(&EXT3_SB(sb)->s_resize_lock);
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if (o_blocks_count != le32_to_cpu(es->s_blocks_count)) {
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ext3_warning(sb, __func__,
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"multiple resizers run on filesystem!");
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unlock_super(sb);
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mutex_unlock(&EXT3_SB(sb)->s_resize_lock);
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ext3_journal_stop(handle);
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err = -EBUSY;
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goto exit_put;
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@ -1059,13 +1060,13 @@ int ext3_group_extend(struct super_block *sb, struct ext3_super_block *es,
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EXT3_SB(sb)->s_sbh))) {
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ext3_warning(sb, __func__,
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"error %d on journal write access", err);
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unlock_super(sb);
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mutex_unlock(&EXT3_SB(sb)->s_resize_lock);
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ext3_journal_stop(handle);
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goto exit_put;
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}
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es->s_blocks_count = cpu_to_le32(o_blocks_count + add);
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ext3_journal_dirty_metadata(handle, EXT3_SB(sb)->s_sbh);
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unlock_super(sb);
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mutex_unlock(&EXT3_SB(sb)->s_resize_lock);
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ext3_debug("freeing blocks %lu through "E3FSBLK"\n", o_blocks_count,
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o_blocks_count + add);
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ext3_free_blocks_sb(handle, sb, o_blocks_count, add, &freed_blocks);
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@ -1929,6 +1929,7 @@ static int ext3_fill_super (struct super_block *sb, void *data, int silent)
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#endif
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INIT_LIST_HEAD(&sbi->s_orphan); /* unlinked but open files */
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mutex_init(&sbi->s_orphan_lock);
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mutex_init(&sbi->s_resize_lock);
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sb->s_root = NULL;
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@ -73,6 +73,7 @@ struct ext3_sb_info {
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struct journal_s * s_journal;
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struct list_head s_orphan;
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struct mutex s_orphan_lock;
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struct mutex s_resize_lock;
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unsigned long s_commit_interval;
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struct block_device *journal_bdev;
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#ifdef CONFIG_JBD_DEBUG
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