- 11 Jul, 2024 40 commits
-
-
Filipe Manana authored
During ordered extent splitting if we find a duplicated ordered extent when attempting to insert the new ordered extent we panic but with a message that has the "zoned:" prefix. This is because the splitting used to be exclusive for zoned filesystems, but as of commit b73a6fd1 ("btrfs: split partial dio bios before submit") it can also be done for non zoned filesystems during direct IO writes. So remove the "zoned:" prefix from the message and mention the split to make it more specific and different from the panic message at insert_ordered_extent(). Reviewed-by:
Josef Bacik <josef@toxicpanda.com> Reviewed-by:
Qu Wenruo <wqu@suse.com> Reviewed-by:
Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by:
Filipe Manana <fdmanana@suse.com> Reviewed-by:
David Sterba <dsterba@suse.com> Signed-off-by:
-
Filipe Manana authored
We never expect an ordered extent insertion to fail due to already having another ordered extent in the tree for the same file offset, since we always wait for existing ordered extents in a range to complete before writing into the range again. So mark the failure checks for the results of tree_insert() as unlikely, to make it clear it's never expected (save exceptional causes like bugs or memory corruptions) and to serve as a hint for the compiler to possibly generate better code. Reviewed-by:
-
Filipe Manana authored
At btrfs_split_ordered_extent(), we are removing and re-inserting the ordered extent that we are trimming, but we don't need to since the trimming doesn't change its position in the red black tree because we don't have overlapping ordered extents (that would imply double allocation of extents) and we know the split length is smaller than the ordered extent's num_bytes field (we checked that early in the function). So drop the remove and re-insert code for the slit ordered extent. Reviewed-by:
-
Filipe Manana authored
There are subtle details about why the root's ordered_extent_lock is held, so add a comment mentioning them. Reviewed-by:
-
Filipe Manana authored
At btrfs_wait_ordered_extents(), there's no point in updating the counters after locking the root's ordered extent lock, as the counters are local. So change this to update the counters before taking the lock. Reviewed-by:
-
Filipe Manana authored
At btrfs_wait_ordered_roots(), there's no point in decrementing the counter after locking fs_info->ordered_root_lock as the counter is local. So change this to decrement the counter before taking the lock. Reviewed-by:
-
David Sterba authored
We can add const to many parameters, this is for clarity and minor addition to safety. There are some minor effects, in the assembly code and .ko measured on release config. This patch does not cover all possible conversions. Signed-off-by: -
Qu Wenruo authored
There is already an error inside that header: #if !defined(__LINUX_SPINLOCK_TYPES_H) # error "Do not include directly, include spinlock_types.h" #endif Thankfully it never get triggered as some other headers have already included spinlock_types.h. However clangd would still do a proper warning on that if only extent_map.h is opened. Fix it by using spinlock_types.h instead. Reviewed-by:
-
Qu Wenruo authored
We have several headers that are including themselves, triggering clangd warnings. Such includes are caused by commit 602035d7 ("btrfs: add forward declarations and headers, part 2"). Just remove such unnecessary include. Reviewed-by:
-
Junchao Sun authored
Generic slab works fine allocating btrfs_qgroup_extent_record structures. It's not necessary to create a dedicated kmem cache that would be created but unused if quotas were not enabled. Let's delete the TODO line. Reviewed-by:
Junchao Sun <sunjunchao2870@gmail.com> Reviewed-by:
-
Qu Wenruo authored
When extent_write_locked_range() generated an inline extent, it would set and finish the writeback for the whole page. Although currently it's safe since subpage disables inline creation, for the sake of consistency, let it go with subpage helpers to set and clear the writeback flags. Reviewed-by:
Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by:
-
Qu Wenruo authored
[BUG] For subpage + zoned case, the following workload can lead to rsv data leak at unmount time: # mkfs.btrfs -f -s 4k $dev # mount $dev $mnt # fsstress -w -n 8 -d $mnt -s 1709539240 0/0: fiemap - no filename 0/1: copyrange read - no filename 0/2: write - no filename 0/3: rename - no source filename 0/4: creat f0 x:0 0 0 0/4: creat add id=0,parent=-1 0/5: writev f0[259 1 0 0 0 0] [778052,113,965] 0 0/6: ioctl(FIEMAP) f0[259 1 0 0 224 887097] [1294220,2291618343991484791,0x10000] -1 0/7: dwrite - xfsctl(XFS_IOC_DIOINFO) f0[259 1 0 0 224 887097] return 25, fallback to stat() 0/7: dwrite f0[259 1 0 0 224 887097] [696320,102400] 0 # umount $mnt The dmesg includes the following rsv leak detection warning (all call trace skipped): ------------[ cut here ]------------ WARNING: CPU: 2 PID: 4528 at fs/btrfs/inode.c:8653 btrfs_destroy_inode+0x1e0/0x200 [btrfs] ---[ end trace 0000000000000000 ]--- ------------[ cut here ]------------ WARNING: CPU: 2 PID: 4528 at fs/btrfs/inode.c:8654 btrfs_destroy_inode+0x1a8/0x200 [btrfs] ---[ end trace 0000000000000000 ]--- ------------[ cut here ]------------ WARNING: CPU: 2 PID: 4528 at fs/btrfs/inode.c:8660 btrfs_destroy_inode+0x1a0/0x200 [btrfs] ---[ end trace 0000000000000000 ]--- BTRFS info (device sda): last unmount of filesystem 1b4abba9-de34-4f07-9e7f-157cf12a18d6 ------------[ cut here ]------------ WARNING: CPU: 3 PID: 4528 at fs/btrfs/block-group.c:4434 btrfs_free_block_groups+0x338/0x500 [btrfs] ---[ end trace 0000000000000000 ]--- BTRFS info (device sda): space_info DATA has 268218368 free, is not full BTRFS info (device sda): space_info total=268435456, used=204800, pinned=0, reserved=0, may_use=12288, readonly=0 zone_unusable=0 BTRFS info (device sda): global_block_rsv: size 0 reserved 0 BTRFS info (device sda): trans_block_rsv: size 0 reserved 0 BTRFS info (device sda): chunk_block_rsv: size 0 reserved 0 BTRFS info (device sda): delayed_block_rsv: size 0 reserved 0 BTRFS info (device sda): delayed_refs_rsv: size 0 reserved 0 ------------[ cut here ]------------ WARNING: CPU: 3 PID: 4528 at fs/btrfs/block-group.c:4434 btrfs_free_block_groups+0x338/0x500 [btrfs] ---[ end trace 0000000000000000 ]--- BTRFS info (device sda): space_info METADATA has 267796480 free, is not full BTRFS info (device sda): space_info total=268435456, used=131072, pinned=0, reserved=0, may_use=262144, readonly=0 zone_unusable=245760 BTRFS info (device sda): global_block_rsv: size 0 reserved 0 BTRFS info (device sda): trans_block_rsv: size 0 reserved 0 BTRFS info (device sda): chunk_block_rsv: size 0 reserved 0 BTRFS info (device sda): delayed_block_rsv: size 0 reserved 0 BTRFS info (device sda): delayed_refs_rsv: size 0 reserved 0 Above $dev is a tcmu-runner emulated zoned HDD, which has a max zone append size of 64K, and the system has 64K page size. [CAUSE] I have added several trace_printk() to show the events (header skipped): > btrfs_dirty_pages: r/i=5/259 dirty start=774144 len=114688 > btrfs_dirty_pages: r/i=5/259 dirty part of page=720896 off_in_page=53248 len_in_page=12288 > btrfs_dirty_pages: r/i=5/259 dirty part of page=786432 off_in_page=0 len_in_page=65536 > btrfs_dirty_pages: r/i=5/259 dirty part of page=851968 off_in_page=0 len_in_page=36864 The above lines show our buffered write has dirtied 3 pages of inode 259 of root 5: 704K 768K 832K 896K I |////I/////////////////I///////////| I 756K 868K |///| is the dirtied range using subpage bitmaps. and 'I' is the page boundary. Meanwhile all three pages (704K, 768K, 832K) have their PageDirty flag set. > btrfs_direct_write: r/i=5/259 start dio filepos=696320 len=102400 Then direct IO write starts, since the range [680K, 780K) covers the beginning part of the above dirty range, we need to writeback the two pages at 704K and 768K. > cow_file_range: r/i=5/259 add ordered extent filepos=774144 len=65536 > extent_write_locked_range: r/i=5/259 locked page=720896 start=774144 len=65536 Now the above 2 lines show that we're writing back for dirty range [756K, 756K + 64K). We only writeback 64K because the zoned device has max zone append size as 64K. > extent_write_locked_range: r/i=5/259 clear dirty for page=786432 !!! The above line shows the root cause. !!! We're calling clear_page_dirty_for_io() inside extent_write_locked_range(), for the page 768K. This is because extent_write_locked_range() can go beyond the current locked page, here we hit the page at 768K and clear its page dirt. In fact this would lead to the desync between subpage dirty and page dirty flags. We have the page dirty flag cleared, but the subpage range [820K, 832K) is still dirty. After the writeback of range [756K, 820K), the dirty flags look like this, as page 768K no longer has dirty flag set. 704K 768K 832K 896K I I | I/////////////| I 820K 868K This means we will no longer writeback range [820K, 832K), thus the reserved data/metadata space would never be properly released. > extent_write_cache_pages: r/i=5/259 skip non-dirty folio=786432 Now even though we try to start writeback for page 768K, since the page is not dirty, we completely skip it at extent_write_cache_pages() time. > btrfs_direct_write: r/i=5/259 dio done filepos=696320 len=0 Now the direct IO finished. > cow_file_range: r/i=5/259 add ordered extent filepos=851968 len=36864 > extent_write_locked_range: r/i=5/259 locked page=851968 start=851968 len=36864 Now we writeback the remaining dirty range, which is [832K, 868K). Causing the range [820K, 832K) never to be submitted, thus leaking the reserved space. This bug only affects subpage and zoned case. For non-subpage and zoned case, we have exactly one sector for each page, thus no such partial dirty cases. For subpage and non-zoned case, we never go into run_delalloc_cow(), and normally all the dirty subpage ranges would be properly submitted inside __extent_writepage_io(). [FIX] Just do not clear the page dirty at all inside extent_write_locked_range(). As __extent_writepage_io() would do a more accurate, subpage compatible clear for page and subpage dirty flags anyway. Now the correct trace would look like this: > btrfs_dirty_pages: r/i=5/259 dirty start=774144 len=114688 > btrfs_dirty_pages: r/i=5/259 dirty part of page=720896 off_in_page=53248 len_in_page=12288 > btrfs_dirty_pages: r/i=5/259 dirty part of page=786432 off_in_page=0 len_in_page=65536 > btrfs_dirty_pages: r/i=5/259 dirty part of page=851968 off_in_page=0 len_in_page=36864 The page dirty part is still the same 3 pages. > btrfs_direct_write: r/i=5/259 start dio filepos=696320 len=102400 > cow_file_range: r/i=5/259 add ordered extent filepos=774144 len=65536 > extent_write_locked_range: r/i=5/259 locked page=720896 start=774144 len=65536 And the writeback for the first 64K is still correct. > cow_file_range: r/i=5/259 add ordered extent filepos=839680 len=49152 > extent_write_locked_range: r/i=5/259 locked page=786432 start=839680 len=49152 Now with the fix, we can properly writeback the range [820K, 832K), and properly release the reserved data/metadata space. Reviewed-by: -
Qu Wenruo authored
If we have a subpage range like this for a 16K page with 4K sectorsize: 0 4K 8K 12K 16K |/////| |//////| | |/////| = dirty range Currently writepage_delalloc() would go through the following steps: - lock range [0, 4K) - run delalloc range for [0, 4K) - lock range [8K, 12K) - run delalloc range for [8K 12K) So far it's fine for regular subpage writeback, as btrfs_run_delalloc_range() can only go into one of run_delalloc_nocow(), cow_file_range() and run_delalloc_compressed(). But there is a special case for zoned subpage, where we will go through run_delalloc_cow(), which would create the ordered extent for the range and immediately submit the range. This would unlock the whole page range, causing all kinds of different ASSERT()s related to locked page. Address the page unlocking problem of run_delalloc_cow(), by changing the workflow to the following one: - lock range [0, 4K) - lock range [8K, 12K) - run delalloc range for [0, 4K) - run delalloc range for [8K, 12K) So that run_delalloc_cow() can only unlock the full page until the last lock user released. To do that: - Utilize subpage locked bitmap So for every delalloc range we found, call btrfs_folio_set_writer_lock() to populate the subpage locked bitmap, and later btrfs_folio_end_all_writers() if the page is fully unlocked. So we know there is a delalloc range that needs to be run later. - Save the @delalloc_end as @last_delalloc_end inside writepage_delalloc() Since subpage locked bitmap is only for ranges inside the page, meanwhile we can have delalloc range ends beyond our page boundary, we have to save the @last_delalloc_end just in case it's beyond our page boundary. Although there is one extra point to notice: - We need to handle errors in previous iteration Since we can have multiple locked delalloc ranges we have to call run_delalloc_ranges() multiple times. If we hit an error half way, we still need to unlock the remaining ranges. Signed-off-by: -
Qu Wenruo authored
Three new helpers are introduced for the incoming subpage delalloc locking change. - btrfs_folio_set_writer_lock() This is to mark specified range with subpage specific writer lock. After calling this, the subpage range can be proper unlocked by btrfs_folio_end_writer_lock() - btrfs_subpage_find_writer_locked() This is to find the writer locked subpage range in a page. With the help of btrfs_folio_set_writer_lock(), it can allow us to record and find previously locked subpage range without extra memory allocation. - btrfs_folio_end_all_writers() This is for the locked_page of __extent_writepage(), as there may be multiple subpage delalloc ranges locked. Reviewed-by:
-
Qu Wenruo authored
Function __extent_writepage_io() is designed to find all dirty ranges of a page, and add the dirty ranges to the bio_ctrl for submission. It requires all the dirtied ranges to be covered by an ordered extent. It gets called in two locations, but one call site is not subpage aware: - __extent_writepage() It gets called when writepage_delalloc() returned 0, which means writepage_delalloc() has handled delalloc for all subpage sectors inside the page. So this call site is OK. - extent_write_locked_range() This call site is utilized by zoned support, and in this case, we may only run delalloc range for a subset of the page, like this: (64K page size) 0 16K 32K 48K 64K |/////| |///////| | In the above case, if extent_write_locked_range() is only triggered for range [0, 16K), __extent_writepage_io() would still try to submit the dirty range of [32K, 48K), then it would not find any ordered extent for it and triggers various ASSERT()s. Fix this problem by: - Introducing @start and @len parameters to specify the range For the first call site, we just pass the whole page, and the behavior is not touched, since run_delalloc_range() for the page should have created all ordered extents for the page. For the second call site, we avoid touching anything beyond the range, thus avoiding the dirty range which is not yet covered by any delalloc range. - Making btrfs_folio_assert_not_dirty() subpage aware The only caller is inside __extent_writepage_io(), and since that caller now accepts a subpage range, we should also check the subpage range other than the whole page. Reviewed-by:
-
Jeff Johnson authored
Fix the 'make W=1' warning: WARNING: modpost: missing MODULE_DESCRIPTION() in fs/btrfs/btrfs.o Signed-off-by:
Jeff Johnson <quic_jjohnson@quicinc.com> Reviewed-by:
-
Anand Jain authored
Drop the variable 'err', reuse the variable 'ret' by reinitializing it to zero where necessary. Signed-off-by:
Anand Jain <anand.jain@oracle.com> Reviewed-by:
-
Anand Jain authored
Fix coding style: rename the return variable to 'ret' in the function btrfs_recover_relocation instead of 'err'. Signed-off-by:
-
Anand Jain authored
A preparatory patch to rename 'err' to 'ret', but ret is already used as an intermediary return value, so first rename 'ret' to 'ret2'. Signed-off-by:
-
Anand Jain authored
In the function btrfs_recover_relocation(), currently the variable 'err' carries the return value and 'ret' holds the intermediary return value. However, in some lines, we don't need this two-step approach; we can directly use 'err'. So, optimize them, which requires reinitializing 'err' to zero at two locations. This is a preparatory patch to fix the code style by renaming 'err' to 'ret'. Signed-off-by:
-
Anand Jain authored
Since err represents the function return value, rename it as ret, and rename the original ret, which serves as a helper return value, to found. Also, optimize the code to continue call btrfs_put_root() for the rest of the root if even after btrfs_orphan_cleanup() returns error. Signed-off-by:
-
Qu Wenruo authored
The following 3 parameters can be cleaned up using btrfs_file_extent structure: - len btrfs_file_extent::num_bytes - orig_block_len btrfs_file_extent::disk_num_bytes - ram_bytes btrfs_file_extent::ram_bytes Reviewed-by:
-
Qu Wenruo authored
Most parameters of create_io_em() can be replaced by the members with the same name inside btrfs_file_extent. Do a direct parameters cleanup here. Reviewed-by:
-
Qu Wenruo authored
All parameters after @filepos of btrfs_alloc_ordered_extent() can be replaced with btrfs_file_extent structure. This patch does the cleanup, meanwhile some points to note: - Move btrfs_file_extent structure to ordered-data.h The structure is needed by both btrfs_alloc_ordered_extent() and can_nocow_extent(), but since btrfs_inode.h includes ordered-data.h, so we need to move the structure to ordered-data.h. - Move the special handling of NOCOW/PREALLOC into btrfs_alloc_ordered_extent() This is to allow btrfs_split_ordered_extent() to properly split them for DIO. For now just move the handling into btrfs_alloc_ordered_extent() to simplify the callers. Reviewed-by:
-
Qu Wenruo authored
The following functions and structures can be simplified using the btrfs_file_extent structure: - can_nocow_extent() No need to return ram_bytes/orig_block_len through the parameter list, the @file_extent parameter contains all the needed info. - can_nocow_file_extent_args The following members are no longer needed: * disk_bytenr This one is confusing as it's not really the btrfs_file_extent_item::disk_bytenr, but where the IO would be, thus it's file_extent::disk_bytenr + file_extent::offset now. * num_bytes Now file_extent::num_bytes. * extent_offset Now file_extent::offset. * disk_num_bytes Now file_extent::disk_num_bytes. Reviewed-by: -
Qu Wenruo authored
The member extent_map::block_start can be calculated from extent_map::disk_bytenr + extent_map::offset for regular extents. And otherwise just extent_map::disk_bytenr. And this is already validated by the validate_extent_map(). Now we can remove the member. However there is a special case in btrfs_create_dio_extent() where we for NOCOW/PREALLOC ordered extents cannot directly use the resulting btrfs_file_extent, as btrfs_split_ordered_extent() cannot handle them yet. So for that call site, we pass file_extent->disk_bytenr + file_extent->num_bytes as disk_bytenr for the ordered extent, and 0 for offset. Reviewed-by:
-
Qu Wenruo authored
The extent_map::block_len is either extent_map::len (non-compressed extent) or extent_map::disk_num_bytes (compressed extent). Since we already have sanity checks to do the cross-checks between the new and old members, we can drop the old extent_map::block_len now. For most call sites, they can manually select extent_map::len or extent_map::disk_num_bytes, since most if not all of them have checked if the extent is compressed. Reviewed-by:
-
Qu Wenruo authored
Since we have extent_map::offset, the old extent_map::orig_start is just extent_map::start - extent_map::offset for non-hole/inline extents. And since the new extent_map::offset is already verified by validate_extent_map() while the old orig_start is not, let's just remove the old member from all call sites. Reviewed-by:
-
Qu Wenruo authored
Since extent_map structure has the all the needed members to represent a file extent directly, we can apply all the file extent sanity checks to an extent map. The new sanity checks will cross check both the old members (block_start/block_len/orig_start) and the new members (disk_bytenr/disk_num_bytes/offset). There is a special case for offset/orig_start/start cross check, we only do such sanity check for compressed extent, as only compressed read/encoded write really utilize orig_start. This can be proved by the cleanup patch of orig_start. The checks happens at the following times: - add_extent_mapping() This is for newly added extent map - replace_extent_mapping() This is for btrfs_drop_extent_map_range() and split_extent_map() - try_merge_map() For a lot of call sites we have to properly populate all the members to pass the sanity check, meanwhile the following code needs extra modification: - setup_file_extents() from inode-tests The file extents layout of setup_file_extents() is already too invalid that tree-checker would reject most of them in real world. However there is just a special unaligned regular extent which has mismatched disk_num_bytes (4096) and ram_bytes (4096 - 1). So instead of dropping the whole test case, here we just unify disk_num_bytes and ram_bytes to 4096 - 1. - test_case_7() from extent-map-tests An extent is inserted with 16K length, but on-disk extent size is only 4K. This means it must be a compressed extent, so set the compressed flag for it. Reviewed-by:
-
Qu Wenruo authored
Introduce two new members for extent_map: - disk_bytenr - offset Both are matching the members with the same name inside btrfs_file_extent_items. For now this patch only touches those members when: - Reading btrfs_file_extent_items from disk - Inserting new holes - Merging two extent maps With the new disk_bytenr and disk_num_bytes, doing merging would be a little more complex, as we have 3 different cases: * Both extent maps are referring to the same data extents |<----- data extent A ----->| |<- em 1 ->|<- em 2 ->| * Both extent maps are referring to different data extents |<-- data extent A -->|<-- data extent B -->| |<- em 1 ->|<- em 2 ->| * One of the extent maps is referring to a merged and larger data extent that covers both extent maps This is not really valid case other than some selftests. So this test case would be removed. A new helper merge_ondisk_extents() is introduced to handle the above valid cases. To properly assign values for those new members, a new btrfs_file_extent parameter is introduced to all the involved call sites. - For NOCOW writes the btrfs_file_extent would be exposed from can_nocow_file_extent(). - For other writes, the members can be easily calculated As most of them have 0 offset and utilizing the whole on-disk data extent. The exception is encoded write, but thankfully that interface provided offset directly and all other needed info. For now, both the old members (block_start/block_len/orig_start) are co-existing with the new members (disk_bytenr/offset), meanwhile all the critical code is still using the old members only. The cleanup will happen later after all the old and new members are properly validated. There would be some re-ordering for the assignment of the extent_map members, now we follow the new ordering: - start and len Or file_pos and num_bytes for other structures. - disk_bytenr and disk_num_bytes - offset and ram_bytes - compression So expect some seemingly unrelated line movement. Reviewed-by: -
Qu Wenruo authored
Currently function can_nocow_extent() only returns members needed for extent_map. However since we will soon change the extent_map structure to be more like btrfs_file_extent_item, we want to expose the expected file extent caused by the NOCOW write for future usage. This introduces a new structure, btrfs_file_extent, to be a more memory access friendly representation of btrfs_file_extent_item. And use that structure to expose the expected file extent caused by the NOCOW write. For now there is no user of the new structure yet. Reviewed-by:
-
Qu Wenruo authored
This would make it very obvious that the member just matches btrfs_file_extent_item::disk_num_bytes. Reviewed-by:
-
Filipe Manana authored
Currently the core of the fiemap code lives in extent_io.c, which does not make any sense because it's not related to extent IO at all (and it was not as well before the big rewrite of fiemap I did some time ago). The entry point for fiemap, btrfs_fiemap(), lives in inode.c since it's an inode operation. Since there's a significant amount of fiemap code, move all of it into a dedicated file, including its entry point inode.c:btrfs_fiemap(). Reviewed-by:
-
Filipe Manana authored
Now that there is a helper to commit the current transaction and we are using it, there's no need for the label and goto statements at ensure_commit_roots_uptodate(). So replace them with direct return statements that call btrfs_commit_current_transaction(). Reviewed-by:
-
Filipe Manana authored
We have several places that attach to the current transaction with btrfs_attach_transaction_barrier() and then commit the transaction if there is one. Add a helper and use it to deduplicate this pattern. Reviewed-by:
-
Filipe Manana authored
At finish_extent_writes_for_zoned() we use btrfs_join_transaction() to catch any running transaction and then commit it. This will however create a new and empty transaction in case there's no running transaction anymore (got committed by the transaction kthread or other task for example) or there's a running transaction finishing its commit and with a state >= TRANS_STATE_UNBLOCKED. In the former case we don't need to do anything while in the second case we just need to wait for the transaction to complete its commit. So improve this by using btrfs_attach_transaction_barrier() instead, which does not create a new transaction if there's none running, and if there's a current transaction that is committing, it will wait for it to fully commit and not create a new transaction. This helps avoiding creating and committing empty transactions, saving IO, time and unnecessary rotation of the backup roots in the super block. Reviewed-by:
-
Filipe Manana authored
At ensure_commit_roots_uptodate() we use btrfs_join_transaction() to catch any running transaction and then commit it. This will however create a new and empty transaction in case there's no running transaction anymore (got committed by the transaction kthread or other task for example) or there's a running transaction finishing its commit and with a state >= TRANS_STATE_UNBLOCKED. In the former case we don't need to do anything while in the second case we just need to wait for the transaction to complete its commit. So improve this by using btrfs_attach_transaction_barrier() instead, which does not create a new transaction if there's none running, and if there's a current transaction that is committing, it will wait for it to fully commit and not create a new transaction. This helps avoiding creating and committing empty transactions, saving IO, time and unnecessary rotation of the backup roots in the super block. Reviewed-by:
-
Filipe Manana authored
Before starting a send operation we have to make sure that every root has its commit root matching the regular root, to that send doesn't find stale inodes in the commit root (inodes that were deleted in the regular root) and fails the inode lookups with -ESTALE. Currently we keep looking for roots used by the send operation and as soon as we find one we commit the current transaction (or a new one since btrfs_join_transaction() creates one if there isn't any running or the running one is in a state >= TRANS_STATE_UNBLOCKED). It's pointless to keep looking until we don't find any, because after the first transaction commit all the other roots are updated too, as they were already tagged in the fs_info->fs_roots_radix radix tree when they were modified in order to have a commit root different from the regular root. Currently we are also always passing the main send root into btrfs_join_transaction(), which despite not having any functional issue, it is not optimal because in case the root wasn't modified we end up adding it to fs_info->fs_roots_radix and then update its root item in the root tree when committing the transaction, causing unnecessary work. So simplify and make this more efficient by removing the looping and by passing the first root we found that is modified as the argument to btrfs_join_transaction(). Reviewed-by:
-
Filipe Manana authored
At btrfs_commit_super(), called in a few contexts such as when unmounting a filesystem, we use btrfs_join_transaction() to catch any running transaction and then commit it. This will however create a new and empty transaction in case there's no running transaction or there's a running transaction with a state >= TRANS_STATE_UNBLOCKED. As we just want to be sure that any existing transaction is fully committed, we can use btrfs_attach_transaction_barrier() instead of btrfs_join_transaction(), therefore avoiding the creation and commit of empty transactions, which only waste IO and causes rotation of the precious backup roots. Example where we create and commit a pointless empty transaction: $ mkfs.btrfs -f /dev/sdj $ btrfs inspect-internal dump-super /dev/sdj | grep -e '^generation' generation 6 $ mount /dev/sdj /mnt/sdj $ touch /mnt/sdj/foo # Commit the currently open transaction. Just 'sync' or wait ~30 # seconds for the transaction kthread to commit it. $ sync $ btrfs inspect-internal dump-super /dev/sdj | grep -e '^generation' generation 7 $ umount /mnt/sdj $ btrfs inspect-internal dump-super /dev/sdj | grep -e '^generation' generation 8 The transaction with id 8 was pointless, an empty transaction that did not achieve anything. Reviewed-by:
-
Filipe Manana authored
When flushing reservations we are using btrfs_join_transaction() to get a handle for the current transaction and then commit it to try to release space. However btrfs_join_transaction() has some undesirable consequences: 1) If there's no running transaction, it will create one, and we will commit it right after. This is unnecessary because it will not release any space, and it will result in unnecessary IO and rotation of backup roots in the superblock; 2) If there's a current transaction and that transaction is committing (its state is >= TRANS_STATE_COMMIT_DOING), it will wait for that transaction to almost finish its commit (for its state to be >= TRANS_STATE_UNBLOCKED) and then start and return a new transaction. We will then commit that new transaction, which is pointless because all we wanted was to wait for the current (previous) transaction to fully finish its commit (state == TRANS_STATE_COMPLETED), and by starting and committing a new transaction we are wasting IO too and causing unnecessary rotation of backup roots in the superblock. So improve this by using btrfs_attach_transaction_barrier() instead, which does not create a new transaction if there's none running, and if there's a current transaction that is committing, it will wait for it to fully commit and not create a new transaction. Reviewed-by:
-
