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mmap-cache: drop Context and boolean flags in Window

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No functional change, just refactoring.
This commit is contained in:
Yu Watanabe
2023-09-30 04:49:53 +09:00
parent 12c2560997
commit 2ebc9cc867
1 changed files with 46 additions and 47 deletions
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93
src/libsystemd/sd-journal/mmap-cache.c
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@@ -16,14 +16,23 @@
#include "sigbus.h"
typedef struct Window Window;
typedef struct Context Context;
typedef enum WindowFlags {
WINDOW_KEEP_ALWAYS = 1u << (MMAP_CACHE_MAX_CONTEXTS + 0),
WINDOW_IN_UNUSED = 1u << (MMAP_CACHE_MAX_CONTEXTS + 1),
WINDOW_INVALIDATED = 1u << (MMAP_CACHE_MAX_CONTEXTS + 2),
_WINDOW_USED_MASK = WINDOW_IN_UNUSED - 1, /* The mask contains all bits that indicate the windows
* is currently in use. Covers the all the object types
* and the additional WINDOW_KEEP_ALWAYS flag. */
} WindowFlags;
#define WINDOW_IS_UNUSED(w) (((w)->flags & _WINDOW_USED_MASK) == 0)
struct Window {
MMapFileDescriptor *fd;
bool invalidated:1;
bool keep_always:1;
bool in_unused:1;
WindowFlags flags;
void *ptr;
uint64_t offset;
@@ -31,21 +40,15 @@ struct Window {
LIST_FIELDS(Window, windows);
LIST_FIELDS(Window, unused);
LIST_HEAD(Context, contexts);
};
struct Context {
Window *window;
LIST_FIELDS(Context, by_window);
};
struct MMapFileDescriptor {
MMapCache *cache;
int fd;
int prot;
bool sigbus;
LIST_HEAD(Window, windows);
};
@@ -62,7 +65,7 @@ struct MMapCache {
LIST_HEAD(Window, unused);
Window *last_unused;
Context contexts[MMAP_CACHE_MAX_CONTEXTS];
Window *windows_by_context[MMAP_CACHE_MAX_CONTEXTS];
};
#define WINDOWS_MIN 64
@@ -96,17 +99,15 @@ static Window* window_unlink(Window *w) {
if (w->ptr)
munmap(w->ptr, w->size);
if (w->in_unused) {
if (FLAGS_SET(w->flags, WINDOW_IN_UNUSED)) {
if (m->last_unused == w)
m->last_unused = w->unused_prev;
LIST_REMOVE(unused, m->unused, w);
}
LIST_FOREACH(by_window, c, w->contexts) {
assert(c->window == w);
c->window = NULL;
}
for (unsigned i = 0; i < MMAP_CACHE_MAX_CONTEXTS; i++)
if (FLAGS_SET(w->flags, 1u << i))
assert_se(TAKE_PTR(m->windows_by_context[i]) == w);
return LIST_REMOVE(windows, w->fd->windows, w);
}
@@ -115,14 +116,14 @@ static void window_invalidate(Window *w) {
assert(w);
assert(w->fd);
if (w->invalidated)
if (FLAGS_SET(w->flags, WINDOW_INVALIDATED))
return;
/* Replace the window with anonymous pages. This is useful when we hit a SIGBUS and want to make sure
* the file cannot trigger any further SIGBUS, possibly overrunning the sigbus queue. */
assert_se(mmap(w->ptr, w->size, w->fd->prot, MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, -1, 0) == w->ptr);
w->invalidated = true;
w->flags |= WINDOW_INVALIDATED;
}
static Window* window_free(Window *w) {
@@ -169,19 +170,20 @@ static Window* window_add(MMapFileDescriptor *f, uint64_t offset, size_t size, v
return LIST_PREPEND(windows, f->windows, w);
}
static void context_detach_window(MMapCache *m, Context *c) {
static void context_detach_window(MMapCache *m, unsigned c) {
Window *w;
assert(m);
assert(c);
assert(c < MMAP_CACHE_MAX_CONTEXTS);
if (!c->window)
return;
w = TAKE_PTR(m->windows_by_context[c]);
if (!w)
return; /* Nothing attached. */
w = TAKE_PTR(c->window);
LIST_REMOVE(by_window, w->contexts, c);
assert(FLAGS_SET(w->flags, 1u << c));
w->flags &= ~(1u << c);
if (!w->contexts && !w->keep_always) {
if (WINDOW_IS_UNUSED(w)) {
/* Not used anymore? */
#if ENABLE_DEBUG_MMAP_CACHE
/* Unmap unused windows immediately to expose use-after-unmap by SIGSEGV. */
@@ -190,33 +192,31 @@ static void context_detach_window(MMapCache *m, Context *c) {
LIST_PREPEND(unused, m->unused, w);
if (!m->last_unused)
m->last_unused = w;
w->in_unused = true;
w->flags |= WINDOW_IN_UNUSED;
#endif
}
}
static void context_attach_window(MMapCache *m, Context *c, Window *w) {
static void context_attach_window(MMapCache *m, unsigned c, Window *w) {
assert(m);
assert(c);
assert(c < MMAP_CACHE_MAX_CONTEXTS);
assert(w);
if (c->window == w)
return;
if (m->windows_by_context[c] == w)
return; /* Already attached. */
context_detach_window(m, c);
if (w->in_unused) {
if (FLAGS_SET(w->flags, WINDOW_IN_UNUSED)) {
/* Used again? */
if (m->last_unused == w)
m->last_unused = w->unused_prev;
LIST_REMOVE(unused, m->unused, w);
w->in_unused = false;
w->flags &= ~WINDOW_IN_UNUSED;
}
c->window = w;
LIST_PREPEND(by_window, w->contexts, c);
m->windows_by_context[c] = w;
w->flags |= (1u << c);
}
static MMapCache* mmap_cache_free(MMapCache *m) {
@@ -322,7 +322,7 @@ static int add_mmap(
int mmap_cache_fd_get(
MMapFileDescriptor *f,
unsigned context,
unsigned c,
bool keep_always,
uint64_t offset,
size_t size,
@@ -330,23 +330,20 @@ int mmap_cache_fd_get(
void **ret) {
MMapCache *m = mmap_cache_fd_cache(f);
Context *c;
Window *w;
int r;
assert(context < MMAP_CACHE_MAX_CONTEXTS);
assert(size > 0);
assert(c < MMAP_CACHE_MAX_CONTEXTS);
assert(ret);
if (f->sigbus)
return -EIO;
c = &f->cache->contexts[context];
/* Check whether the current context is the right one already */
if (window_matches(c->window, f, offset, size)) {
if (window_matches(m->windows_by_context[c], f, offset, size)) {
m->n_context_cache_hit++;
w = c->window;
w = m->windows_by_context[c];
goto found;
}
@@ -369,7 +366,9 @@ int mmap_cache_fd_get(
return r;
found:
w->keep_always = w->keep_always || keep_always;
if (keep_always)
w->flags |= WINDOW_KEEP_ALWAYS;
context_attach_window(m, c, w);
*ret = (uint8_t*) w->ptr + (offset - w->offset);
return 0;