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Fri, 5 Apr 2024 03:27:31 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap2.dmz-prg2.suse.org with ESMTPSA id 6u7hFqNvD2a+aQAAn2gu4w (envelope-from ) for ; Fri, 05 Apr 2024 03:27:31 +0000 From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH v3 0/3] btrfs: more explaination on extent_map members Date: Fri, 5 Apr 2024 13:57:10 +1030 Message-ID: X-Mailer: git-send-email 2.44.0 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Flag: NO X-Spam-Score: -3.01 X-Rspamd-Action: no action X-Rspamd-Queue-Id: 9B0BE1F461 X-Spam-Level: X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_CONTAINS_FROM(1.00)[]; R_MISSING_CHARSET(0.50)[]; R_DKIM_ALLOW(-0.20)[suse.com:s=susede1]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; ARC_NA(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_ONE(0.00)[1]; PREVIOUSLY_DELIVERED(0.00)[linux-btrfs@vger.kernel.org]; RCVD_TLS_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:dkim]; DKIM_SIGNED(0.00)[suse.com:s=susede1]; FUZZY_BLOCKED(0.00)[rspamd.com]; TO_DN_NONE(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; MIME_TRACE(0.00)[0:+]; DKIM_TRACE(0.00)[suse.com:+] [REPO] https://github.com/adam900710/linux.git/ em_cleanup [CHANGELOG] v3: - Rebased to latest for-next branch - Further comments polishment - Coding style update to follow the guideline v2: - Add Filipe's cleanup on mod_start/mod_len These two members are no longer utilized, saving me quite some time on digging into their usage. - Update the comments of the extent_map structure To make them more readable and less confusing. - Further cleanup for inline extent_map reading - A new patch to do extra sanity checks for create_io_em() Firstly pure NOCOW writes should not call create_io_em(), secondly with the new knowledge of extent_map, it's easier to do extra sanity checks for the already pretty long parameter list. Btrfs uses extent_map to represent a in-memory file extent. There are severam members that are 1:1 mappe in on-disk file extent items and extent maps: - extent_map::start == key.offset - extent_map::len == file_extent_num_bytes - extent_map::ram_bytes == file_extent_ram_bytes But that's all, the remaining are pretty different: - Use block_start to indicate holes/inline extents Meanwhile btrfs on-disk file extent items go with a dedicated type for inline extents, and disk_bytenr 0 for holes. - Weird block_start/orig_block_len/orig_start In theory we can directly go with the same file_extent_disk_bytenr, file_extent_disk_num_bytes and file_extent_offset to calculate the remaining members (block_start/orig_start/orig_block_len/block_len). But for whatever reason, we didn't go that path and have a hell of weird and inconsistent calculation for them. I do not have the confidence to handle the mess yet, but as the first step, I would add comments for those members mostly according to btrfs_extent_item_to_extent_map(), and hopefully we can improve the situation in not-far-away future. Qu Wenruo (3): btrfs: add extra comments on extent_map members btrfs: simplify the inline extent map creation btrfs: add extra sanity checks for create_io_em() fs/btrfs/extent_map.h | 52 ++++++++++++++++++++++++++++++++++++++++++- fs/btrfs/file-item.c | 20 ++++++++--------- fs/btrfs/inode.c | 40 ++++++++++++++++++++++++++++++++- 3 files changed, 100 insertions(+), 12 deletions(-)