- 22 Feb, 2021 8 commits
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Josef Bacik authored
The tree checker checks the extent ref hash at read and write time to make sure we do not corrupt the file system. Generally extent references go inline, but if we have enough of them we need to make an item, which looks like key.objectid = <bytenr> key.type = <BTRFS_EXTENT_DATA_REF_KEY|BTRFS_TREE_BLOCK_REF_KEY> key.offset = hash(tree, owner, offset) However if key.offset collide with an unrelated extent reference we'll simply key.offset++ until we get something that doesn't collide. Obviously this doesn't match at tree checker time, and thus we error while writing out the transaction. This is relatively easy to reproduce, simply do something like the following xfs_io -f -c "pwrite 0 1M" file offset=2 for i in {0..10000} do xfs_io -c "reflink file 0 ${offset}M 1M" file offset=$(( offset + 2 )) done xfs_io -c "reflink file 0 17999258914816 1M" file xfs_io -c "reflink file 0 35998517829632 1M" file xfs_io -c "reflink file 0 53752752058368 1M" file btrfs filesystem sync And the sync will error out because we'll abort the transaction. The magic values above are used because they generate hash collisions with the first file in the main subvol. The fix for this is to remove the hash value check from tree checker, as we have no idea which offset ours should belong to. Reported-by:Tuomas Lähdekorpi <tuomas.lahdekorpi@gmail.com> Fixes: 0785a9aa ("btrfs: tree-checker: Add EXTENT_DATA_REF check") CC: stable@vger.kernel.org # 5.4+ Reviewed-by:
Filipe Manana <fdmanana@suse.com> Signed-off-by:
Josef Bacik <josef@toxicpanda.com> Reviewed-by:
David Sterba <dsterba@suse.com> [ add comment] Signed-off-by:
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Filipe Manana authored
When creating a snapshot we check if the current number of swap files, in the root, is non-zero, and if it is, we error out and warn that we can not create the snapshot because there are active swap files. However this is racy because when a task started activation of a swap file, another task might have started already snapshot creation and might have seen the counter for the number of swap files as zero. This means that after the swap file is activated we may end up with a snapshot of the same root successfully created, and therefore when the first write to the swap file happens it has to fall back into COW mode, which should never happen for active swap files. Basically what can happen is: 1) Task A starts snapshot creation and enters ioctl.c:create_snapshot(). There it sees that root->nr_swapfiles has a value of 0 so it continues; 2) Task B enters btrfs_swap_activate(). It is not aware that another task started snapshot creation but it did not finish yet. It increments root->nr_swapfiles from 0 to 1; 3) Task B checks that the file meets all requirements to be an active swap file - it has NOCOW set, there are no snapshots for the inode's root at the moment, no file holes, no reflinked extents, etc; 4) Task B returns success and now the file is an active swap file; 5) Task A commits the transaction to create the snapshot and finishes. The swap file's extents are now shared between the original root and the snapshot; 6) A write into an extent of the swap file is attempted - there is a snapshot of the file's root, so we fall back to COW mode and therefore the physical location of the extent changes on disk. So fix this by taking the snapshot lock during swap file activation before locking the extent range, as that is the order in which we lock these during buffered writes. Fixes: ed46ff3d ("Btrfs: support swap files") CC: stable@vger.kernel.org # 5.4+ Reviewed-by:
Anand Jain <anand.jain@oracle.com> Reviewed-by:
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Filipe Manana authored
When we active a swap file, at btrfs_swap_activate(), we acquire the exclusive operation lock to prevent the physical location of the swap file extents to be changed by operations such as balance and device replace/resize/remove. We also call there can_nocow_extent() which, among other things, checks if the block group of a swap file extent is currently RO, and if it is we can not use the extent, since a write into it would result in COWing the extent. However we have no protection against a scrub operation running after we activate the swap file, which can result in the swap file extents to be COWed while the scrub is running and operating on the respective block group, because scrub turns a block group into RO before it processes it and then back again to RW mode after processing it. That means an attempt to write into a swap file extent while scrub is processing the respective block group, will result in COWing the extent, changing its physical location on disk. Fix this by making sure that block groups that have extents that are used by active swap files can not be turned into RO mode, therefore making it not possible for a scrub to turn them into RO mode. When a scrub finds a block group that can not be turned to RO due to the existence of extents used by swap files, it proceeds to the next block group and logs a warning message that mentions the block group was skipped due to active swap files - this is the same approach we currently use for balance. Fixes: ed46ff3d ("Btrfs: support swap files") CC: stable@vger.kernel.org # 5.4+ Reviewed-by:
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Filipe Manana authored
During the nocow writeback path, we currently iterate the rbtree of block groups twice: once for checking if the target block group is RO with the call to btrfs_extent_readonly()), and once again for getting a nocow reference on the block group with a call to btrfs_inc_nocow_writers(). Since btrfs_inc_nocow_writers() already returns false when the target block group is RO, remove the call to btrfs_extent_readonly(). Not only we avoid searching the blocks group rbtree twice, it also helps reduce contention on the lock that protects it (specially since it is a spin lock and not a read-write lock). That may make a noticeable difference on very large filesystems, with thousands of allocated block groups. Reviewed-by:
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Nikolay Borisov authored
During allocation the allocator will try to allocate an extent using cluster policy. Once the current cluster is exhausted it will remove the entry under btrfs_free_cluster::lock and subsequently acquire btrfs_free_space_ctl::tree_lock to dispose of the already-deleted entry and adjust btrfs_free_space_ctl::total_bitmap. This poses a problem because there exists a race condition between removing the entry under one lock and doing the necessary accounting holding a different lock since extent freeing only uses the 2nd lock. This can result in the following situation: T1: T2: btrfs_alloc_from_cluster insert_into_bitmap <holds tree_lock> if (entry->bytes == 0) if (block_group && !list_empty(&block_group->cluster_list)) { rb_erase(entry) spin_unlock(&cluster->lock); (total_bitmaps is still 4) spin_lock(&cluster->lock); <doesn't find entry in cluster->root> spin_lock(&ctl->tree_lock); <goes to new_bitmap label, adds <blocked since T2 holds tree_lock> <a new entry and calls add_new_bitmap> recalculate_thresholds <crashes, due to total_bitmaps becoming 5 and triggering an ASSERT> To fix this ensure that once depleted, the cluster entry is deleted when both cluster lock and tree locks are held in the allocator (T1), this ensures that even if there is a race with a concurrent insert_into_bitmap call it will correctly find the entry in the cluster and add the new space to it. CC: <stable@vger.kernel.org> # 4.4+ Reviewed-by:Nikolay Borisov <nborisov@suse.com> Signed-off-by:
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Qu Wenruo authored
Currently check_compressed_csum() completely relies on sectorsize == PAGE_SIZE to do checksum verification for compressed extents. To make it subpage compatible, this patch will: - Do extra calculation for the csum range Since we have multiple sectors inside a page, we need to only hash the range we want, not the full page anymore. - Do sector-by-sector hash inside the page With this patch and previous conversion on btrfs_submit_compressed_read(), now we can read subpage compressed extents properly, and do proper csum verification. Reviewed-by:
Qu Wenruo <wqu@suse.com> Signed-off-by:
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Qu Wenruo authored
For compressed read, we always submit page read using page size. This doesn't work well with subpage, as for subpage one page can contain several sectors. Such submission will read range out of what we want, and cause problems. Thankfully to make it subpage compatible, we only need to change how the last page of the compressed extent is read. Instead of always adding a full page to the compressed read bio, if we're at the last page, calculate the size using compressed length, so that we only add part of the range into the compressed read bio. Since we are here, also change the PAGE_SIZE used in lookup_extent_mapping() to sectorsize. This modification won't cause any functional change, as lookup_extent_mapping() can handle the case where the search range is larger than found extent range. Reviewed-by:
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Ira Weiny authored
When a qstripe is required an extra page is allocated and mapped. There were 3 problems: 1) There is no corresponding call of kunmap() for the qstripe page. 2) There is no reason to map the qstripe page more than once if the number of bits set in rbio->dbitmap is greater than one. 3) There is no reason to map the parity page and unmap it each time through the loop. The page memory can continue to be reused with a single mapping on each iteration by raid6_call.gen_syndrome() without remapping. So map the page for the duration of the loop. Similarly, improve the algorithm by mapping the parity page just 1 time. Fixes: 5a6ac9ea ("Btrfs, raid56: support parity scrub on raid56") CC: stable@vger.kernel.org # 4.4.x: c17af965: btrfs: raid56: simplify tracking of Q stripe presence CC: stable@vger.kernel.org # 4.4.x Signed-off-by:
Ira Weiny <ira.weiny@intel.com> Reviewed-by:
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- 09 Feb, 2021 32 commits
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Naohiro Aota authored
This final patch adds the ZONED incompat flag to the supported flags and enables to mount ZONED flagged file system. Reviewed-by:
Naohiro Aota <naohiro.aota@wdc.com> Reviewed-by:
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Naohiro Aota authored
Since the zoned filesystem requires sequential write out of metadata, we cannot proceed with a hole in tree-log pages. When such a hole exists, btree_write_cache_pages() will return -EAGAIN. This happens when someone, e.g., a concurrent transaction commit, writes a dirty extent in this tree-log commit. If we are not going to wait for the extents, we can hope the concurrent writing fills the hole for us. So, we can ignore the error in this case and hope the next write will succeed. If we want to wait for them and got the error, we cannot wait for them because it will cause a deadlock. So, let's bail out to a full commit in this case. Reviewed-by:
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Naohiro Aota authored
This is the 3/3 patch to enable tree-log on zoned filesystems. The allocation order of nodes of "fs_info->log_root_tree" and nodes of "root->log_root" is not the same as the writing order of them. So, the writing causes unaligned write errors. Reorder the allocation of them by delaying allocation of the root node of "fs_info->log_root_tree," so that the node buffers can go out sequentially to devices. Cc: Filipe Manana <fdmanana@gmail.com> Reviewed-by:
Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by:
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Naohiro Aota authored
This is the 2/3 patch to enable tree-log on zoned filesystems. Since we can start more than one log transactions per subvolume simultaneously, nodes from multiple transactions can be allocated interleaved. Such mixed allocation results in non-sequential writes at the time of a log transaction commit. The nodes of the global log root tree (fs_info->log_root_tree), also have the same problem with mixed allocation. Serializes log transactions by waiting for a committing transaction when someone tries to start a new transaction, to avoid the mixed allocation problem. We must also wait for running log transactions from another subvolume, but there is no easy way to detect which subvolume root is running a log transaction. So, this patch forbids starting a new log transaction when other subvolumes already allocated the global log root tree. Reviewed-by:
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Naohiro Aota authored
This is the 1/3 patch to enable tree log on zoned filesystems. The tree-log feature does not work on a zoned filesystem as is. Blocks for a tree-log tree are allocated mixed with other metadata blocks and btrfs writes and syncs the tree-log blocks to devices at the time of fsync(), which has a different timing than a global transaction commit. As a result, both writing tree-log blocks and writing other metadata blocks become non-sequential writes that zoned filesystems must avoid. Introduce a dedicated block group for tree-log blocks, so that tree-log blocks and other metadata blocks can be separate write streams. As a result, each write stream can now be written to devices separately. "fs_info->treelog_bg" tracks the dedicated block group and assigns "treelog_bg" on-demand on tree-log block allocation time. This commit extends the zoned block allocator to use the block group. Reviewed-by:
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Naohiro Aota authored
This is a preparation patch for the next patch. Split alloc_log_tree() into two parts. The first one allocating the tree structure, remains in alloc_log_tree() and the second part allocating the tree node, which is moved into btrfs_alloc_log_tree_node(). Also export the latter part is to be used in the next patch. Reviewed-by:
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Naohiro Aota authored
When a bad checksum is found and if the filesystem has a mirror of the damaged data, we read the correct data from the mirror and writes it to damaged blocks. This however, violates the sequential write constraints of a zoned block device. We can consider three methods to repair an IO failure in zoned filesystems: (1) Reset and rewrite the damaged zone (2) Allocate new device extent and replace the damaged device extent to the new extent (3) Relocate the corresponding block group Method (1) is most similar to a behavior done with regular devices. However, it also wipes non-damaged data in the same device extent, and so it unnecessary degrades non-damaged data. Method (2) is much like device replacing but done in the same device. It is safe because it keeps the device extent until the replacing finish. However, extending device replacing is non-trivial. It assumes "src_dev->physical == dst_dev->physical". Also, the extent mapping replacing function should be extended to support replacing device extent position in one device. Method (3) invokes relocation of the damaged block group and is straightforward to implement. It relocates all the mirrored device extents, so it potentially is a more costly operation than method (1) or (2). But it relocates only used extents which reduce the total IO size. Let's apply method (3) for now. In the future, we can extend device-replace and apply method (2). For protecting a block group gets relocated multiple time with multiple IO errors, this commit introduces "relocating_repair" bit to show it's now relocating to repair IO failures. Also it uses a new kthread "btrfs-relocating-repair", not to block IO path with relocating process. This commit also supports repairing in the scrub process. Reviewed-by: -
Naohiro Aota authored
Currently fallocate() is disabled on a zoned filesystem. Since current relocation process relies on preallocation to move file data extents, it must be handled differently. On a zoned filesystem, we just truncate the inode to the size that we wanted to pre-allocate. Then, we flush dirty pages on the file before finishing the relocation process. run_delalloc_zoned() will handle all the allocations and submit IOs to the underlying layers. Reviewed-by:
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Naohiro Aota authored
This is 4/4 patch to implement device-replace on zoned filesystems. Even after the copying is done, the write pointers of the source device and the destination device may not be synchronized. For example, when the last allocated extent is freed before device-replace process, the extent is not copied, leaving a hole there. Synchronize the write pointers by writing zeroes to the destination device. Reviewed-by:
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Naohiro Aota authored
This is 3/4 patch to implement device-replace on zoned filesystems. This commit implements copying. To do this, it tracks the write pointer during the device replace process. As device-replace's copy process is smart enough to only copy used extents on the source device, we have to fill the gap to honor the sequential write requirement in the target device. The device-replace process on zoned filesystems must copy or clone all the extents in the source device exactly once. So, we need to ensure allocations started just before the dev-replace process to have their corresponding extent information in the B-trees. finish_extent_writes_for_zoned() implements that functionality, which basically is the removed code in the commit 042528f8 ("Btrfs: fix block group remaining RO forever after error during device replace"). Reviewed-by:
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Naohiro Aota authored
This is 2/4 patch to implement device replace for zoned filesystems. In zoned mode, a block group must be either copied (from the source device to the target device) or cloned (to both devices). Implement the cloning part. If a block group targeted by an IO is marked to copy, we should not clone the IO to the destination device, because the block group is eventually copied by the replace process. This commit also handles cloning of device reset. Reviewed-by:
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Naohiro Aota authored
This is the 1/4 patch to support device-replace on zoned filesystems. We have two types of IOs during the device replace process. One is an IO to "copy" (by the scrub functions) all the device extents from the source device to the destination device. The other one is an IO to "clone" (by handle_ops_on_dev_replace()) new incoming write IOs from users to the source device into the target device. Cloning incoming IOs can break the sequential write rule in on target device. When a write is mapped in the middle of a block group, the IO is directed to the middle of a target device zone, which breaks the sequential write requirement. However, the cloning function cannot be disabled since incoming IOs targeting already copied device extents must be cloned so that the IO is executed on the target device. We cannot use dev_replace->cursor_{left,right} to determine whether a bio is going to a not yet copied region. Since we have a time gap between finishing btrfs_scrub_dev() and rewriting the mapping tree in btrfs_dev_replace_finishing(), we can have a newly allocated device extent which is never cloned nor copied. So the point is to copy only already existing device extents. This patch introduces mark_block_group_to_copy() to mark existing block groups as a target of copying. Then, handle_ops_on_dev_replace() and dev-replace can check the flag to do their job. Also, btrfs_finish_block_group_to_copy() will check if the copied stripe is the last stripe in the block group. With the last stripe copied, the to_copy flag is finally disabled. Afterwards we can safely clone incoming IOs on this block group. Reviewed-by: -
Naohiro Aota authored
On zoned filesystems, btrfs uses per-fs zoned_meta_io_lock to serialize the metadata write IOs. Even with this serialization, write bios sent from btree_write_cache_pages can be reordered by async checksum workers as these workers are per CPU and not per zone. To preserve write bio ordering, we disable async metadata checksum on a zoned filesystem. This does not result in lower performance with HDDs as a single CPU core is fast enough to do checksum for a single zone write stream with the maximum possible bandwidth of the device. If multiple zones are being written simultaneously, HDD seek overhead lowers the achievable maximum bandwidth, resulting again in a per zone checksum serialization not affecting the performance. Reviewed-by:
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Naohiro Aota authored
When truncating a file, file buffers which have already been allocated but not yet written may be truncated. Truncating these buffers could cause breakage of a sequential write pattern in a block group if the truncated blocks are for example followed by blocks allocated to another file. To avoid this problem, always wait for write out of all unwritten buffers before proceeding with the truncate execution. Signed-off-by:
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Naohiro Aota authored
We cannot use zone append for writing metadata, because the B-tree nodes have references to each other using logical address. Without knowing the address in advance, we cannot construct the tree in the first place. So we need to serialize write IOs for metadata. We cannot add a mutex around allocation and submission because metadata blocks are allocated in an earlier stage to build up B-trees. Add a zoned_meta_io_lock and hold it during metadata IO submission in btree_write_cache_pages() to serialize IOs. Furthermore, this adds a per-block group metadata IO submission pointer "meta_write_pointer" to ensure sequential writing, which can break when attempting to write back blocks in an unfinished transaction. If the writing out failed because of a hole and the write out is for data integrity (WB_SYNC_ALL), it returns EAGAIN. A caller like fsync() code should handle this properly e.g. by falling back to a full transaction commit. Reviewed-by:
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Naohiro Aota authored
If more than one IO is issued for one file extent, these IO can be written to separate regions on a device. Since we cannot map one file extent to such a separate area on a zoned filesystem, we need to follow the "one IO == one ordered extent" rule. The normal buffered, uncompressed and not pre-allocated write path (used by cow_file_range()) sometimes does not follow this rule. It can write a part of an ordered extent when specified a region to write e.g., when its called from fdatasync(). Introduce a dedicated (uncompressed buffered) data write path for zoned filesystems, that will COW the region and write it at once. Reviewed-by:
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Naohiro Aota authored
Likewise to buffered IO, enable zone append writing for direct IO when its used on a zoned block device. Reviewed-by:
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Naohiro Aota authored
Enable zone append writing for zoned mode. When using zone append, a bio is issued to the start of a target zone and the device decides to place it inside the zone. Upon completion the device reports the actual written position back to the host. Three parts are necessary to enable zone append mode. First, modify the bio to use REQ_OP_ZONE_APPEND in btrfs_submit_bio_hook() and adjust the bi_sector to point the beginning of the zone. Second, record the returned physical address (and disk/partno) to the ordered extent in end_bio_extent_writepage() after the bio has been completed. We cannot resolve the physical address to the logical address because we can neither take locks nor allocate a buffer in this end_bio context. So, we need to record the physical address to resolve it later in btrfs_finish_ordered_io(). And finally, rewrite the logical addresses of the extent mapping and checksum data according to the physical address using btrfs_rmap_block. If the returned address matches the originally allocated address, we can skip this rewriting process. Reviewed-by:
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Johannes Thumshirn authored
A following patch will add another caller of btrfs_lookup_ordered_extent(), but from a bio's endio context. btrfs_lookup_ordered_extent() uses spin_lock_irq() which unconditionally disables interrupts. Change this to spin_lock_irqsave() so interrupts aren't disabled and re-enabled unconditionally. Reviewed-by:
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Johannes Thumshirn authored
On a zoned filesystem, cache if a block group is on a sequential write only zone. On sequential write only zones, we can use REQ_OP_ZONE_APPEND for writing data, therefore provide btrfs_use_zone_append() to figure out if IO is targeting a sequential write only zone and we can use REQ_OP_ZONE_APPEND for data writing. Reviewed-by:
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Naohiro Aota authored
btrfs_rmap_block currently reverse-maps the physical addresses on all devices to the corresponding logical addresses. Extend the function to match to a specified device. The old functionality of querying all devices is left intact by specifying NULL as target device. A block_device instead of a btrfs_device is passed into btrfs_rmap_block, as this function is intended to reverse-map the result of a bio, which only has a block_device. Also export the function for later use. Reviewed-by:
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Johannes Thumshirn authored
To ensure that an ordered extent maps to a contiguous region on disk, we need to maintain a "one bio == one ordered extent" rule. Ensure that constructing bio does not span more than an ordered extent. Reviewed-by:
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Naohiro Aota authored
For a zone append write, the device decides the location the data is being written to. Therefore we cannot ensure that two bios are written consecutively on the device. In order to ensure that an ordered extent maps to a contiguous region on disk, we need to maintain a "one bio == one ordered extent" rule. Implement splitting of an ordered extent and extent map on bio submission to adhere to the rule. extract_ordered_extent() hooks into btrfs_submit_data_bio() and splits the corresponding ordered extent so that the ordered extent's region fits into one bio and the corresponding device limits. Several sanity checks need to be done in extract_ordered_extent() e.g. - We cannot split once end_bio'd ordered extent because we cannot divide ordered->bytes_left for the split ones - We do not expect a compressed ordered extent - We should not have checksum list because we omit the list splitting. Since the function is called before btrfs_wq_submit_bio() or btrfs_csum_one_bio(), this should be always ensured. We also need to split an extent map by creating a new one. If not, unpin_extent_cache() complains about the difference between the start of the extent map and the file's logical offset. Reviewed-by:
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Naohiro Aota authored
Zoned filesystems use REQ_OP_ZONE_APPEND bios for writing to actual devices. Let btrfs_end_bio() and btrfs_op be aware of it, by mapping REQ_OP_ZONE_APPEND to BTRFS_MAP_WRITE and using btrfs_op() instead of bio_op(). Reviewed-by:
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Naohiro Aota authored
A zoned device has its own hardware restrictions e.g. max_zone_append_size when using REQ_OP_ZONE_APPEND. To follow these restrictions, use bio_add_zone_append_page() instead of bio_add_page(). We need target device to use bio_add_zone_append_page(), so this commit reads the chunk information to cache the target device to btrfs_io_bio(bio)->device. Caching only the target device is sufficient here as zoned filesystems only supports the single profile at the moment. Once more profiles will be supported btrfs_io_bio can hold an extent_map to be able to check for the restrictions of all devices the btrfs_bio will be mapped to. Reviewed-by:
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Naohiro Aota authored
Factor out adding a page to a bio from submit_extent_page(). The page is added only when bio_flags are the same, contiguous and the added page fits in the same stripe as pages in the bio. Condition checks are reordered to allow early return to avoid possibly heavy btrfs_bio_fits_in_stripe() calling. Reviewed-by:
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Naohiro Aota authored
We must reset the zones of a deleted unused block group to rewind the zones' write pointers to the zones' start. To do this, we can use the DISCARD_SYNC code to do the reset when the filesystem is running on zoned devices. Reviewed-by:
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Naohiro Aota authored
Since the allocation info of a tree log node is not recorded in the extent tree, calculate_alloc_pointer() cannot detect this node, so the pointer can be over a tree node. Replaying the log calls btrfs_remove_free_space() for each node in the log tree. So, advance the pointer after the node to not allocate over it. Reviewed-by:
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Naohiro Aota authored
Tree manipulating operations like merging nodes often release once-allocated tree nodes. Such nodes are cleaned so that pages in the node are not uselessly written out. On zoned volumes, however, such optimization blocks the following IOs as the cancellation of the write out of the freed blocks breaks the sequential write sequence expected by the device. Introduce a list of clean and unwritten extent buffers that have been released in a transaction. Redirty the buffers so that btree_write_cache_pages() can send proper bios to the devices. Besides it clears the entire content of the extent buffer not to confuse raw block scanners e.g. 'btrfs check'. By clearing the content, csum_dirty_buffer() complains about bytenr mismatch, so avoid the checking and checksum using newly introduced buffer flag EXTENT_BUFFER_NO_CHECK. Reviewed-by:
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Naohiro Aota authored
Implement a sequential extent allocator for zoned filesystems. This allocator only needs to check if there is enough space in the block group after the allocation pointer to satisfy the extent allocation request. Therefore the allocator never manages bitmaps or clusters. Also, add assertions to the corresponding functions. As zone append writing is used, it would be unnecessary to track the allocation offset, as the allocator only needs to check available space. But by tracking and returning the offset as an allocated region, we can skip modification of ordered extents and checksum information when there is no IO reordering. Reviewed-by:
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Naohiro Aota authored
In a zoned filesystem a once written then freed region is not usable until the underlying zone has been reset. So we need to distinguish such unusable space from usable free space. Therefore we need to introduce the "zone_unusable" field to the block group structure, and "bytes_zone_unusable" to the space_info structure to track the unusable space. Pinned bytes are always reclaimed to the unusable space. But, when an allocated region is returned before using e.g., the block group becomes read-only between allocation time and reservation time, we can safely return the region to the block group. For the situation, this commit introduces "btrfs_add_free_space_unused". This behaves the same as btrfs_add_free_space() on regular filesystem. On zoned filesystems, it rewinds the allocation offset. Because the read-only bytes tracks free but unusable bytes when the block group is read-only, we need to migrate the zone_unusable bytes to read-only bytes when a block group is marked read-only. Reviewed-by:
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Naohiro Aota authored
Conventional zones do not have a write pointer, so we cannot use it to determine the allocation offset for sequential allocation if a block group contains a conventional zone. But instead, we can consider the end of the highest addressed extent in the block group for the allocation offset. For new block group, we cannot calculate the allocation offset by consulting the extent tree, because it can cause deadlock by taking extent buffer lock after chunk mutex, which is already taken in btrfs_make_block_group(). Since it is a new block group anyways, we can simply set the allocation offset to 0. Reviewed-by:
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