| /linux-6.8/fs/btrfs/ |
| D | space-info.c | 26 * 1) space_info. This is the ultimate arbiter of how much space we can use.
29 * reservations we care about total_bytes - SUM(space_info->bytes_) when
34 * metadata reservation we have. You can see the comment in the block_rsv
38 * 3) btrfs_calc*_size. These are the worst case calculations we used based
39 * on the number of items we will want to modify. We have one for changing
40 * items, and one for inserting new items. Generally we use these helpers to
46 * We call into either btrfs_reserve_data_bytes() or
47 * btrfs_reserve_metadata_bytes(), depending on which we're looking for, with
48 * num_bytes we want to reserve.
65 * Assume we are unable to simply make the reservation because we do not have
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| D | delalloc-space.c | 25 * We call into btrfs_reserve_data_bytes() for the user request bytes that
26 * they wish to write. We make this reservation and add it to
27 * space_info->bytes_may_use. We set EXTENT_DELALLOC on the inode io_tree
29 * make a real allocation if we are pre-allocating or doing O_DIRECT.
32 * At writepages()/prealloc/O_DIRECT time we will call into
33 * btrfs_reserve_extent() for some part or all of this range of bytes. We
37 * may allocate a smaller on disk extent than we previously reserved.
48 * This is the simplest case, we haven't completed our operation and we know
49 * how much we reserved, we can simply call
62 * We keep track of two things on a per inode bases
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| /linux-6.8/arch/powerpc/mm/nohash/ |
| D | tlb_low_64e.S | 91 /* We need _PAGE_PRESENT and _PAGE_ACCESSED set */
93 /* We do the user/kernel test for the PID here along with the RW test
95 /* We pre-test some combination of permissions to avoid double
98 * We move the ESR:ST bit into the position of _PAGE_BAP_SW in the PTE
103 * writeable, we will take a new fault later, but that should be
106 * We also move ESR_ST in _PAGE_DIRTY position
109 * MAS1 is preset for all we need except for TID that needs to
137 * We are entered with:
176 /* Now we build the MAS:
219 /* We need to check if it was an instruction miss */
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| /linux-6.8/drivers/md/bcache/ |
| D | journal.h | 9 * never spans two buckets. This means (not implemented yet) we can resize the
15 * We also keep some things in the journal header that are logically part of the
20 * rewritten when we want to move/wear level the main journal.
22 * Currently, we don't journal BTREE_REPLACE operations - this will hopefully be
25 * moving gc we work around it by flushing the btree to disk before updating the
35 * We track this by maintaining a refcount for every open journal entry, in a
38 * zero, we pop it off - thus, the size of the fifo tells us the number of open
41 * We take a refcount on a journal entry when we add some keys to a journal
42 * entry that we're going to insert (held by struct btree_op), and then when we
43 * insert those keys into the btree the btree write we're setting up takes a
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| D | bset.h | 17 * We use two different functions for validating bkeys, bch_ptr_invalid and
27 * them on disk, just unnecessary work - so we filter them out when resorting
30 * We can't filter out stale keys when we're resorting, because garbage
32 * unless we're rewriting the btree node those stale keys still exist on disk.
34 * We also implement functions here for removing some number of sectors from the
44 * There could be many of them on disk, but we never allow there to be more than
45 * 4 in memory - we lazily resort as needed.
47 * We implement code here for creating and maintaining auxiliary search trees
48 * (described below) for searching an individial bset, and on top of that we
62 * Since keys are variable length, we can't use a binary search on a bset - we
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| /linux-6.8/fs/xfs/ |
| D | xfs_log_cil.c | 23 * recover, so we don't allow failure here. Also, we allocate in a context that
24 * we don't want to be issuing transactions from, so we need to tell the
27 * We don't reserve any space for the ticket - we are going to steal whatever
28 * space we require from transactions as they commit. To ensure we reserve all
29 * the space required, we need to set the current reservation of the ticket to
30 * zero so that we know to steal the initial transaction overhead from the
42 * set the current reservation to zero so we know to steal the basic in xlog_cil_ticket_alloc()
62 * We can't rely on just the log item being in the CIL, we have to check
80 * current sequence, we're in a new checkpoint. in xlog_item_in_current_chkpt()
140 * We're in the middle of switching cil contexts. Reset the in xlog_cil_push_pcp_aggregate()
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| D | xfs_log_priv.h | 74 * By covering, we mean changing the h_tail_lsn in the last on-disk
83 * might include space beyond the EOF. So if we just push the EOF a
91 * system is idle. We need two dummy transaction because the h_tail_lsn
103 * we are done covering previous transactions.
104 * NEED -- logging has occurred and we need a dummy transaction
106 * DONE -- we were in the NEED state and have committed a dummy
108 * NEED2 -- we detected that a dummy transaction has gone to the
110 * DONE2 -- we committed a dummy transaction when in the NEED2 state.
112 * There are two places where we switch states:
114 * 1.) In xfs_sync, when we detect an idle log and are in NEED or NEED2.
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| D | xfs_discard.c | 25 * We need to walk the filesystem free space and issue discards on the free
26 * space that meet the search criteria (size and location). We cannot issue
28 * still marked as busy. To serialise against extent state changes whilst we are
29 * gathering extents to trim, we must hold the AGF lock to lock out other
32 * However, we cannot just hold the AGF for the entire AG free space walk whilst
33 * we issue discards on each free space that is found. Storage devices can have
36 * extent can take a *long* time. Whilst we are doing this walk, nothing else
37 * can access the AGF, and we can stall transactions and hence the log whilst
41 * Hence we need to take a leaf from the bulkstat playbook. It takes the AGI
47 * We can't do this exactly with free space - once we drop the AGF lock, the
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| D | xfs_log.c | 89 * We need to make sure the buffer pointer returned is naturally aligned for the
90 * biggest basic data type we put into it. We have already accounted for this
93 * However, this padding does not get written into the log, and hence we have to
98 * We also add space for the xlog_op_header that describes this region in the
99 * log. This prepends the data region we return to the caller to copy their data
101 * is not 8 byte aligned, we have to be careful to ensure that we align the
102 * start of the buffer such that the region we return to the call is 8 byte
256 * Hence when we are woken here, it may be that the head of the in xlog_grant_head_wake()
259 * reservation we require. However, if the AIL has already in xlog_grant_head_wake()
260 * pushed to the target defined by the old log head location, we in xlog_grant_head_wake()
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| /linux-6.8/net/ipv4/ |
| D | tcp_vegas.c | 15 * o We do not change the loss detection or recovery mechanisms of
19 * only every-other RTT during slow start, we increase during
22 * we use the rate at which ACKs come back as the "actual"
24 * o To speed convergence to the right rate, we set the cwnd
25 * to achieve the right ("actual") rate when we exit slow start.
26 * o To filter out the noise caused by delayed ACKs, we use the
55 /* There are several situations when we must "re-start" Vegas:
60 * o when we send a packet and there is no outstanding
63 * In these circumstances we cannot do a Vegas calculation at the
64 * end of the first RTT, because any calculation we do is using
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| /linux-6.8/fs/xfs/scrub/ |
| D | agb_bitmap.c | 19 * We know that the btree query_all function starts at the left edge and walks
20 * towards the right edge of the tree. Therefore, we know that we can walk up
22 * to the first record/key in that block, we haven't seen this block before;
23 * and therefore we need to remember that we saw this block in the btree.
32 * the first btree record, we'll observe that bc_levels[0].ptr == 1, so we
33 * record that we saw block 1. Then we observe that bc_levels[1].ptr == 1, so
34 * we record block 4. The list is [1, 4].
36 * For the second btree record, we see that bc_levels[0].ptr == 2, so we exit
39 * For the 101st btree record, we've moved onto leaf block 2. Now
40 * bc_levels[0].ptr == 1 again, so we record that we saw block 2. We see that
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| D | alloc_repair.c | 48 * AG. Therefore, we can recreate the free extent records in an AG by looking
60 * walking the rmapbt records, we create a second bitmap @not_allocbt_blocks to
72 * The OWN_AG bitmap itself isn't needed after this point, so what we really do
83 * written to the new btree indices. We reconstruct both bnobt and cntbt at
84 * the same time since we've already done all the work.
86 * We use the prefix 'xrep_abt' here because we regenerate both free space
118 * Next block we anticipate seeing in the rmap records. If the next
119 * rmap record is greater than next_agbno, we have found unused space.
126 /* Longest free extent we found in the AG. */
138 * Make sure the busy extent list is clear because we can't put extents in xrep_setup_ag_allocbt()
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| /linux-6.8/Documentation/filesystems/xfs/ |
| D | xfs-delayed-logging-design.rst | 15 We begin with an overview of transactions in XFS, followed by describing how
16 transaction reservations are structured and accounted, and then move into how we
18 reservations bounds. At this point we need to explain how relogging works. With
113 individual modification is atomic, the chain is *not atomic*. If we crash half
140 complete, we can explicitly tag a transaction as synchronous. This will trigger
145 throughput to the IO latency limitations of the underlying storage. Instead, we
161 available to write the modification into the journal before we start making
164 log in the worst case. This means that if we are modifying a btree in the
165 transaction, we have to reserve enough space to record a full leaf-to-root split
166 of the btree. As such, the reservations are quite complex because we have to
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| /linux-6.8/fs/bcachefs/ |
| D | bset.h | 21 * We use two different functions for validating bkeys, bkey_invalid and
27 * them on disk, just unnecessary work - so we filter them out when resorting
30 * We can't filter out stale keys when we're resorting, because garbage
32 * unless we're rewriting the btree node those stale keys still exist on disk.
34 * We also implement functions here for removing some number of sectors from the
44 * There could be many of them on disk, but we never allow there to be more than
45 * 4 in memory - we lazily resort as needed.
47 * We implement code here for creating and maintaining auxiliary search trees
48 * (described below) for searching an individial bset, and on top of that we
62 * Since keys are variable length, we can't use a binary search on a bset - we
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| /linux-6.8/arch/powerpc/kexec/ |
| D | core_64.c | 44 * Since we use the kernel fault handlers and paging code to in machine_kexec_prepare()
45 * handle the virtual mode, we must make sure no destination in machine_kexec_prepare()
52 /* We also should not overwrite the tce tables */ in machine_kexec_prepare()
85 * We rely on kexec_load to create a lists that properly in copy_segments()
87 * We will still crash if the list is wrong, but at least in copy_segments()
120 * After this call we may not use anything allocated in dynamic in kexec_copy_flush()
128 * we need to clear the icache for all dest pages sometime, in kexec_copy_flush()
145 mb(); /* make sure our irqs are disabled before we say they are */ in kexec_smp_down()
152 * Now every CPU has IRQs off, we can clear out any pending in kexec_smp_down()
170 /* Make sure each CPU has at least made it to the state we need. in kexec_prepare_cpus_wait()
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| /linux-6.8/drivers/misc/vmw_vmci/ |
| D | vmci_route.c | 33 * which comes from the VMX, so we know it is coming from a in vmci_route()
36 * To avoid inconsistencies, test these once. We will test in vmci_route()
37 * them again when we do the actual send to ensure that we do in vmci_route()
49 * If this message already came from a guest then we in vmci_route()
57 * We must be acting as a guest in order to send to in vmci_route()
63 /* And we cannot send if the source is the host context. */ in vmci_route()
71 * then they probably mean ANY, in which case we in vmci_route()
87 * If it is not from a guest but we are acting as a in vmci_route()
88 * guest, then we need to send it down to the host. in vmci_route()
89 * Note that if we are also acting as a host then this in vmci_route()
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| /linux-6.8/drivers/usb/dwc2/ |
| D | hcd_queue.c | 31 /* If we get a NAK, wait this long before retrying */
120 * @num_bits: The number of bits we need per period we want to reserve
122 * @interval: How often we need to be scheduled for the reservation this
126 * the interval or we return failure right away.
127 * @only_one_period: Normally we'll allow picking a start anywhere within the
128 * first interval, since we can still make all repetition
130 * here then we'll return failure if we can't fit within
133 * The idea here is that we want to schedule time for repeating events that all
138 * To keep things "simple", we'll represent our schedule with a bitmap that
140 * but does mean that we need to handle things specially (and non-ideally) if
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| /linux-6.8/Documentation/filesystems/ |
| D | directory-locking.rst | 10 When taking the i_rwsem on multiple non-directory objects, we
11 always acquire the locks in order by increasing address. We'll call
22 * lock the directory we are accessing (shared)
26 * lock the directory we are accessing (exclusive)
73 in its own right; it may happen as part of lookup. We speak of the
74 operations on directory trees, but we obviously do not have the full
75 picture of those - especially for network filesystems. What we have
77 Trees grow as we do operations; memory pressure prunes them. Normally
78 that's not a problem, but there is a nasty twist - what should we do
83 possibility that directory we see in one place gets moved by the server
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| D | idmappings.rst | 23 on, we will always prefix ids with ``u`` or ``k`` to make it clear whether
24 we're talking about an id in the upper or lower idmapset.
42 that make it easier to understand how we can translate between idmappings. For
43 example, we know that the inverse idmapping is an order isomorphism as well::
49 Given that we are dealing with order isomorphisms plus the fact that we're
50 dealing with subsets we can embed idmappings into each other, i.e. we can
51 sensibly translate between different idmappings. For example, assume we've been
61 Because we're dealing with order isomorphic subsets it is meaningful to ask
64 mapping ``k11000`` up to ``u1000``. Afterwards, we can map ``u1000`` down using
69 If we were given the same task for the following three idmappings::
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| /linux-6.8/drivers/gpu/drm/i915/ |
| D | i915_request.c | 73 * We could extend the life of a context to beyond that of all in i915_fence_get_timeline_name()
75 * or we just give them a false name. Since in i915_fence_get_timeline_name()
130 * freed when the slab cache itself is freed, and so we would get in i915_fence_release()
139 * We do not hold a reference to the engine here and so have to be in i915_fence_release()
140 * very careful in what rq->engine we poke. The virtual engine is in i915_fence_release()
141 * referenced via the rq->context and we released that ref during in i915_fence_release()
142 * i915_request_retire(), ergo we must not dereference a virtual in i915_fence_release()
143 * engine here. Not that we would want to, as the only consumer of in i915_fence_release()
148 * we know that it will have been processed by the HW and will in i915_fence_release()
154 * power-of-two we assume that rq->engine may still be a virtual in i915_fence_release()
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| /linux-6.8/kernel/irq/ |
| D | spurious.c | 26 * We wait here for a poller to finish.
28 * If the poll runs on this CPU, then we yell loudly and return
32 * We wait until the poller is done and then recheck disabled and
33 * action (about to be disabled). Only if it's still active, we return
86 * All handlers must agree on IRQF_SHARED, so we test just the in try_one_irq()
209 * We need to take desc->lock here. note_interrupt() is called in __report_bad_irq()
210 * w/o desc->lock held, but IRQ_PROGRESS set. We might race in __report_bad_irq()
244 /* We didn't actually handle the IRQ - see if it was misrouted? */ in try_misrouted_irq()
249 * But for 'irqfixup == 2' we also do it for handled interrupts if in try_misrouted_irq()
260 * Since we don't get the descriptor lock, "action" can in try_misrouted_irq()
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| /linux-6.8/drivers/gpu/drm/i915/gt/ |
| D | intel_execlists_submission.c | 24 * shouldn't we just need a set of those per engine command streamer? This is
35 * Regarding the creation of contexts, we have:
43 * like before) we need:
50 * more complex, because we don't know at creation time which engine is going
51 * to use them. To handle this, we have implemented a deferred creation of LR
55 * gets populated for a given engine once we receive an execbuffer. If later
56 * on we receive another execbuffer ioctl for the same context but a different
57 * engine, we allocate/populate a new ringbuffer and context backing object and
61 * only allowed with the render ring, we can allocate & populate them right
96 * we use a NULL second context) or the first two requests have unique IDs.
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| /linux-6.8/arch/openrisc/mm/ |
| D | fault.c | 59 * We fault-in kernel-space virtual memory on-demand. The in do_page_fault()
62 * NOTE! We MUST NOT take any locks for this case. We may in do_page_fault()
68 * mappings we don't have to walk all processes pgdirs and in do_page_fault()
69 * add the high mappings all at once. Instead we do it as they in do_page_fault()
82 /* If exceptions were enabled, we can reenable them here */ in do_page_fault()
100 * If we're in an interrupt or have no user in do_page_fault()
101 * context, we must not take the fault.. in do_page_fault()
125 * we get page-aligned addresses so we can only check in do_page_fault()
126 * if we're within a page from usp, but that might be in do_page_fault()
137 * Ok, we have a good vm_area for this memory access, so in do_page_fault()
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| /linux-6.8/Documentation/driver-api/thermal/ |
| D | cpu-idle-cooling.rst | 25 because of the OPP density, we can only choose an OPP with a power
35 If we can remove the static and the dynamic leakage for a specific
38 injection period, we can mitigate the temperature by modulating the
47 At a specific OPP, we can assume that injecting idle cycle on all CPUs
49 idle state target residency, we lead to dropping the static and the
69 We use a fixed duration of idle injection that gives an acceptable
132 - It is less than or equal to the latency we tolerate when the
134 user experience, reactivity vs performance trade off we want. This
137 - It is greater than the idle state’s target residency we want to go
138 for thermal mitigation, otherwise we end up consuming more energy.
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| /linux-6.8/fs/ocfs2/cluster/ |
| D | quorum.c | 7 /* This quorum hack is only here until we transition to some more rational
17 * So we declare that a node which has given up on connecting to a majority
20 * There are huge opportunities for races here. After we give up on a node's
21 * connection we need to wait long enough to give heartbeat an opportunity
22 * to declare the node as truly dead. We also need to be careful with the
23 * race between when we see a node start heartbeating and when we connect
78 * other nodes in the cluster may consider us dead at that time so we
79 * want to "fence" ourselves so that we don't scribble on the disk
82 * least close some of those gaps. When we have real fencing, this can
112 * if we can't talk to the majority we're hosed */ in o2quo_make_decision()
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