Revision e9f53353e166a67dfe4f8295100f8ac39d6cf10b authored by Daejun Park on 06 January 2021, 01:32:42 UTC, committed by Theodore Ts'o on 15 January 2021, 19:41:31 UTC
In the fast commit, it adds REQ_FUA and REQ_PREFLUSH on each fast commit block when barrier is enabled. However, in recovery phase, ext4 compares CRC value in the tail. So it is sufficient to add REQ_FUA and REQ_PREFLUSH on the block that has tail. Signed-off-by: Daejun Park <daejun7.park@samsung.com> Reviewed-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com> Link: https://lore.kernel.org/r/20210106013242epcms2p5b6b4ed8ca86f29456fdf56aa580e74b4@epcms2p5 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
1 parent 6b4b8e6
atomic_bitops.txt
=============
Atomic bitops
=============
While our bitmap_{}() functions are non-atomic, we have a number of operations
operating on single bits in a bitmap that are atomic.
API
---
The single bit operations are:
Non-RMW ops:
test_bit()
RMW atomic operations without return value:
{set,clear,change}_bit()
clear_bit_unlock()
RMW atomic operations with return value:
test_and_{set,clear,change}_bit()
test_and_set_bit_lock()
Barriers:
smp_mb__{before,after}_atomic()
All RMW atomic operations have a '__' prefixed variant which is non-atomic.
SEMANTICS
---------
Non-atomic ops:
In particular __clear_bit_unlock() suffers the same issue as atomic_set(),
which is why the generic version maps to clear_bit_unlock(), see atomic_t.txt.
RMW ops:
The test_and_{}_bit() operations return the original value of the bit.
ORDERING
--------
Like with atomic_t, the rule of thumb is:
- non-RMW operations are unordered;
- RMW operations that have no return value are unordered;
- RMW operations that have a return value are fully ordered.
- RMW operations that are conditional are unordered on FAILURE,
otherwise the above rules apply. In the case of test_and_{}_bit() operations,
if the bit in memory is unchanged by the operation then it is deemed to have
failed.
Except for a successful test_and_set_bit_lock() which has ACQUIRE semantics and
clear_bit_unlock() which has RELEASE semantics.
Since a platform only has a single means of achieving atomic operations
the same barriers as for atomic_t are used, see atomic_t.txt.
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