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This article will explain in detail how to handle the discard operation in FileJournal. The editor thinks it is very practical, so I share it with you for reference. I hope you can get something after reading this article.

The do_discard () function in the FileJournal class is responsible for handling the trim operation. In this function, the ioctl (fd, BLKDISCARD, range) function is called to complete the submission of the trim operation, and finally the trim operation of the SSD is completed by the operating system and hardware. The do_discard () function call relationship of FileJournal and its processing flow are as follows:

FileStore::mount () calls the mount () function when the FileStore class is initialized

| | _ _ struct SyncThread.create () starts the synchronization thread in the mount () function |

| | _ FileStore::sync_entry () |

| | _ ApplyManager::commit_finish () |

| | _ FileJournal::committed_thru () |

| | _ FileJournal::queue_completions_thru () |

| | _ Finisher::queue (completions_items) |

| | _ finisher_cond.Signal () |

| | _ _ do_discard () supports discard operation for disks corresponding to FileJournal, then call the do_discard () function to complete the function (this function is an optimization operation for disks such as SSD) |

| | _ blkdev.c::block_device_discard () |

| | _ ioctl (fd, BLKDISCARD, range) |

The finisher_cond.Signal () function wakes up the Finisher::finisher_thread_entry () function, which then handles tasks on the finisher_queue queue.

Finisher::finisher_thread_entry ()

| | _ _ Context::complete (0) iterates through all tasks on the finisher_queue queue and calls the complete () function of the task |

This is the end of this article on "what is the flow of discard operations in FileJournal?". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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