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writeback: fix pin_sb_for_writeback
We need to check for s_instances to make sure we don't bother working against a filesystem that is beeing unmounted, and we need to call put_super to make sure a superblock is freed when we race against umount. Also no need to keep sb_lock after we got a reference on it. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
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@ -534,19 +534,21 @@ select_queue:
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static bool pin_sb_for_writeback(struct super_block *sb)
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{
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spin_lock(&sb_lock);
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if (list_empty(&sb->s_instances)) {
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spin_unlock(&sb_lock);
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return false;
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}
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sb->s_count++;
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spin_unlock(&sb_lock);
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if (down_read_trylock(&sb->s_umount)) {
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if (sb->s_root) {
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spin_unlock(&sb_lock);
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if (sb->s_root)
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return true;
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}
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/*
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* umounted, drop rwsem again and fall through to failure
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*/
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up_read(&sb->s_umount);
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}
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sb->s_count--;
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spin_unlock(&sb_lock);
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put_super(sb);
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return false;
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}
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