kernel/git/stable/linux.git/fs/btrfs/block-rsv.h, branch master

btrfs: add METADATA_REMAP chunk type

2026-02-03T06:54:27+00:00

Add a new METADATA_REMAP chunk type, which is a metadata chunk that holds the remap tree. This is needed for bootstrapping purposes: the remap tree can't itself be remapped, and must be relocated the existing way, by COWing every leaf. The remap tree can't go in the SYSTEM chunk as space there is limited, because a copy of the chunk item gets placed in the superblock. The changes in fs/btrfs/volumes.h are because we're adding a new block group type bit after the profile bits, and so can no longer rely on the const_ilog2 trick. The sizing to 32MB per chunk, matching the SYSTEM chunk, is an estimate here, we can adjust it later if it proves to be too big or too small. This works out to be ~500,000 remap items, which for a 4KB block size covers ~2GB of remapped data in the worst case and ~500TB in the best case. Reviewed-by: Boris Burkov Signed-off-by: Mark Harmstone Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: add block reserve for treelog

2025-05-15T12:30:53+00:00

We need to add a dedicated block_rsv for tree-log, because the block_rsv serves for a tree node allocation in btrfs_alloc_tree_block(). Currently, tree-log tree uses fs_info->empty_block_rsv, which is shared across trees and points to the normal metadata space_info. Instead, we add a dedicated block_rsv and that block_rsv can use the dedicated sub-space_info. Reviewed-by: Johannes Thumshirn Signed-off-by: Naohiro Aota Signed-off-by: David Sterba

btrfs: constify more pointer parameters

2024-09-10T14:51:22+00:00

Continue adding const to 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. Signed-off-by: David Sterba

btrfs: add forward declarations and headers, part 2

2024-03-04T15:24:49+00:00

Do a cleanup in more headers: - add forward declarations for types referenced by pointers - add includes when types need them This fixes potential compilation problems if the headers are reordered or the missing includes are not provided indirectly. Signed-off-by: David Sterba

btrfs: fix data race at btrfs_use_block_rsv() when accessing block reserve

2024-02-22T11:15:12+00:00

At btrfs_use_block_rsv() we read the size of a block reserve without locking its spinlock, which makes KCSAN complain because the size of a block reserve is always updated while holding its spinlock. The report from KCSAN is the following: [653.313148] BUG: KCSAN: data-race in btrfs_update_delayed_refs_rsv [btrfs] / btrfs_use_block_rsv [btrfs] [653.314755] read to 0x000000017f5871b8 of 8 bytes by task 7519 on cpu 0: [653.314779] btrfs_use_block_rsv+0xe4/0x2f8 [btrfs] [653.315606] btrfs_alloc_tree_block+0xdc/0x998 [btrfs] [653.316421] btrfs_force_cow_block+0x220/0xe38 [btrfs] [653.317242] btrfs_cow_block+0x1ac/0x568 [btrfs] [653.318060] btrfs_search_slot+0xda2/0x19b8 [btrfs] [653.318879] btrfs_del_csums+0x1dc/0x798 [btrfs] [653.319702] __btrfs_free_extent.isra.0+0xc24/0x2028 [btrfs] [653.320538] __btrfs_run_delayed_refs+0xd3c/0x2390 [btrfs] [653.321340] btrfs_run_delayed_refs+0xae/0x290 [btrfs] [653.322140] flush_space+0x5e4/0x718 [btrfs] [653.322958] btrfs_preempt_reclaim_metadata_space+0x102/0x2f8 [btrfs] [653.323781] process_one_work+0x3b6/0x838 [653.323800] worker_thread+0x75e/0xb10 [653.323817] kthread+0x21a/0x230 [653.323836] __ret_from_fork+0x6c/0xb8 [653.323855] ret_from_fork+0xa/0x30 [653.323887] write to 0x000000017f5871b8 of 8 bytes by task 576 on cpu 3: [653.323906] btrfs_update_delayed_refs_rsv+0x1a4/0x250 [btrfs] [653.324699] btrfs_add_delayed_data_ref+0x468/0x6d8 [btrfs] [653.325494] btrfs_free_extent+0x76/0x120 [btrfs] [653.326280] __btrfs_mod_ref+0x6a8/0x6b8 [btrfs] [653.327064] btrfs_dec_ref+0x50/0x70 [btrfs] [653.327849] walk_up_proc+0x236/0xa50 [btrfs] [653.328633] walk_up_tree+0x21c/0x448 [btrfs] [653.329418] btrfs_drop_snapshot+0x802/0x1328 [btrfs] [653.330205] btrfs_clean_one_deleted_snapshot+0x184/0x238 [btrfs] [653.330995] cleaner_kthread+0x2b0/0x2f0 [btrfs] [653.331781] kthread+0x21a/0x230 [653.331800] __ret_from_fork+0x6c/0xb8 [653.331818] ret_from_fork+0xa/0x30 So add a helper to get the size of a block reserve while holding the lock. Reading the field while holding the lock instead of using the data_race() annotation is used in order to prevent load tearing. Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: fix data races when accessing the reserved amount of block reserves

2024-02-22T11:15:06+00:00

At space_info.c we have several places where we access the ->reserved field of a block reserve without taking the block reserve's spinlock first, which makes KCSAN warn about a data race since that field is always updated while holding the spinlock. The reports from KCSAN are like the following: [117.193526] BUG: KCSAN: data-race in btrfs_block_rsv_release [btrfs] / need_preemptive_reclaim [btrfs] [117.195148] read to 0x000000017f587190 of 8 bytes by task 6303 on cpu 3: [117.195172] need_preemptive_reclaim+0x222/0x2f0 [btrfs] [117.195992] __reserve_bytes+0xbb0/0xdc8 [btrfs] [117.196807] btrfs_reserve_metadata_bytes+0x4c/0x120 [btrfs] [117.197620] btrfs_block_rsv_add+0x78/0xa8 [btrfs] [117.198434] btrfs_delayed_update_inode+0x154/0x368 [btrfs] [117.199300] btrfs_update_inode+0x108/0x1c8 [btrfs] [117.200122] btrfs_dirty_inode+0xb4/0x140 [btrfs] [117.200937] btrfs_update_time+0x8c/0xb0 [btrfs] [117.201754] touch_atime+0x16c/0x1e0 [117.201789] filemap_read+0x674/0x728 [117.201823] btrfs_file_read_iter+0xf8/0x410 [btrfs] [117.202653] vfs_read+0x2b6/0x498 [117.203454] ksys_read+0xa2/0x150 [117.203473] __s390x_sys_read+0x68/0x88 [117.203495] do_syscall+0x1c6/0x210 [117.203517] __do_syscall+0xc8/0xf0 [117.203539] system_call+0x70/0x98 [117.203579] write to 0x000000017f587190 of 8 bytes by task 11 on cpu 0: [117.203604] btrfs_block_rsv_release+0x2e8/0x578 [btrfs] [117.204432] btrfs_delayed_inode_release_metadata+0x7c/0x1d0 [btrfs] [117.205259] __btrfs_update_delayed_inode+0x37c/0x5e0 [btrfs] [117.206093] btrfs_async_run_delayed_root+0x356/0x498 [btrfs] [117.206917] btrfs_work_helper+0x160/0x7a0 [btrfs] [117.207738] process_one_work+0x3b6/0x838 [117.207768] worker_thread+0x75e/0xb10 [117.207797] kthread+0x21a/0x230 [117.207830] __ret_from_fork+0x6c/0xb8 [117.207861] ret_from_fork+0xa/0x30 So add a helper to get the reserved amount of a block reserve while holding the lock. The value may be not be up to date anymore when used by need_preemptive_reclaim() and btrfs_preempt_reclaim_metadata_space(), but that's ok since the worst it can do is cause more reclaim work do be done sooner rather than later. Reading the field while holding the lock instead of using the data_race() annotation is used in order to prevent load tearing. Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: move btrfs_check_trunc_cache_free_space into block-rsv.c

2023-06-19T11:59:24+00:00

This is completely related to block rsv's, move it out of the free space cache code and into block-rsv.c. Reviewed-by: Johannes Thumshirn Signed-off-by: Josef Bacik Signed-off-by: David Sterba

btrfs: simplify variables in btrfs_block_rsv_refill()

2023-04-17T16:01:19+00:00

At btrfs_block_rsv_refill(), there's no point in initializing the 'num_bytes' variable to 0 and then, after taking the block reserve's spinlock, initializing it to the value of the 'min_reserved' parameter. So just get rid of the 'num_bytes' local variable and rename the 'min_reserved' parameter to 'num_bytes'. Reviewed-by: Josef Bacik Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: simplify percent calculation helpers, rename div_factor

2022-12-05T17:00:48+00:00

The div_factor* helpers calculate fraction or percentage fraction. The name is a bit confusing, we use it only for percentage calculations and there are two helpers. There's a helper mult_frac that's for general fractions, that tries to be accurate but we multiply and divide by small numbers so we can use the div_u64 helper. Rename the div_factor* helpers and use 1..100 percentage range, also drop the case checking for percentage == 100, it's never hit. The conversions: * div_factor calculates tenths and the numbers need to be adjusted * div_factor_fine is direct replacement Signed-off-by: David Sterba

btrfs: add dependencies to fs.h and block-rsv.h

2022-12-05T17:00:45+00:00

There's several structures that are embedded inside of fs_info.h, so if we don't have all the proper includes when we include fs.h we'll get a variety of compile errors. I fixed this by adding a temporary c file that just had #include "fs.h" and then added include files until the compiler stopped complaining. Reviewed-by: Johannes Thumshirn Signed-off-by: Josef Bacik Reviewed-by: David Sterba Signed-off-by: David Sterba