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copy: safeguard writeout flag

This commit is contained in:
Thomas Schoebel-Theuer 2022-02-22 07:14:40 +01:00 committed by Thomas Schoebel-Theuer
parent b53b3777d4
commit 7c59774177
3 changed files with 21 additions and 12 deletions
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31
kernel/mars_copy.c
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@ -77,10 +77,10 @@
#include "mars_copy.h" #include "mars_copy.h"
int mars_copy_overlap = 1; /* Always leave at 1, disable only for throughput _testing_.
EXPORT_SYMBOL_GPL(mars_copy_overlap); * 0 = ONLY FOR EXPERTS => may lead to INCONSISTENCIES
* 1 = only obey the start order, but not the completion order
/* Always leave at 1, disable only for throughput _testing_ */ */
int mars_copy_strict_write_order = 1; int mars_copy_strict_write_order = 1;
int mars_copy_timeout = 180; int mars_copy_timeout = 180;
@ -795,6 +795,17 @@ restart:
if (READ_ONCE(st->active[1])) { if (READ_ONCE(st->active[1])) {
goto idle; goto idle;
} }
/* Attention! overlapped IO behind EOF could
* lead to temporary inconsistent state of the
* file, because the write order may be different from
* strict O_APPEND behaviour.
*
* Notice: temporary inconsistencies _behind_ EOF
* cannot be compensated by the page cache.
* If the machine crashes right during such a
* temporary inconsistency, unnecessary DefectiveLog
* (or similar) is likely to appear.
*/
/* start writeout */ /* start writeout */
status = _make_mref(brick, index, 1, mref0->ref_data, status = _make_mref(brick, index, 1, mref0->ref_data,
pos, pos + mref0->ref_len, pos, pos + mref0->ref_len,
@ -805,13 +816,13 @@ restart:
next_state = COPY_STATE_RESET; next_state = COPY_STATE_RESET;
break; break;
} }
/* Attention! overlapped IO behind EOF could /*
* lead to temporary inconsistent state of the * Attention: set the writeout flag _after_ actual
* file, because the write order may be different from * IO had been started.
* strict O_APPEND behaviour.
*/ */
if (mars_copy_overlap) if (mars_copy_strict_write_order)
st->writeout = true; WRITE_ONCE(st->writeout, true);
next_state = COPY_STATE_WRITTEN; next_state = COPY_STATE_WRITTEN;
/* fallthrough */ /* fallthrough */
goto label_COPY_STATE_WRITTEN; goto label_COPY_STATE_WRITTEN;

1
kernel/mars_copy.h
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@ -30,7 +30,6 @@
#define INPUT_B 1 #define INPUT_B 1
#define COPY_INPUT_NR 2 #define COPY_INPUT_NR 2
extern int mars_copy_overlap;
extern int mars_copy_strict_write_order; extern int mars_copy_strict_write_order;
extern int mars_copy_timeout; extern int mars_copy_timeout;
extern int mars_copy_read_prio; extern int mars_copy_read_prio;

1
kernel/sy_old/mars_proc.c
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@ -655,7 +655,6 @@ struct ctl_table mars_table[] = {
VEC_INT_ENTRY("mem_alloc_max", brick_mem_alloc_count, 0600, BRICK_MAX_ORDER+1), VEC_INT_ENTRY("mem_alloc_max", brick_mem_alloc_count, 0600, BRICK_MAX_ORDER+1),
#endif #endif
INT_ENTRY("io_flying_count", mars_global_io_flying, 0400), INT_ENTRY("io_flying_count", mars_global_io_flying, 0400),
INT_ENTRY("copy_overlap", mars_copy_overlap, 0600),
INT_ENTRY("copy_strict_write_order", mars_copy_strict_write_order, 0600), INT_ENTRY("copy_strict_write_order", mars_copy_strict_write_order, 0600),
INT_ENTRY("copy_timeout", mars_copy_timeout, 0600), INT_ENTRY("copy_timeout", mars_copy_timeout, 0600),
INT_ENTRY("copy_read_prio", mars_copy_read_prio, 0600), INT_ENTRY("copy_read_prio", mars_copy_read_prio, 0600),