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log: Only check for FALLOC_FL_COLLAPSE_RANGE availability at runtime

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log.c has several #ifdefs on FALLOC_FL_COLLAPSE_RANGE that won't attempt
to use it if not defined.  But even if the value is defined at compile
time, it might not be available in the runtime kernel, so we need to check
for errors from a fallocate() call and fall back to other methods.

Simplify this to only need the runtime check by using linux_dep.h to define
FALLOC_FL_COLLAPSE_RANGE if it's not in the kernel headers.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2024-11-08 13:53:27 +11:00 committed by Stefano Brivio
parent 58fa5508bd
commit b84cd05098
3 changed files with 8 additions and 13 deletions
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5
Makefile
View file

@ -59,11 +59,6 @@ ifeq ($(shell :|$(CC) -fstack-protector-strong -S -xc - -o - >/dev/null 2>&1; ec
FLAGS += -fstack-protector-strong
endif
C := \#define _GNU_SOURCE\n\#include <fcntl.h>\nint x = FALLOC_FL_COLLAPSE_RANGE;
ifeq ($(shell printf "$(C)" | $(CC) -S -xc - -o - >/dev/null 2>&1; echo $$?),0)
EXTRA_SYSCALLS += fallocate
endif
prefix ?= /usr/local
exec_prefix ?= $(prefix)
bindir ?= $(exec_prefix)/bin

6
linux_dep.h
View file

@ -119,4 +119,10 @@ struct tcp_info_linux {
*/
};
#include <linux/falloc.h>
#ifndef FALLOC_FL_COLLAPSE_RANGE
#define FALLOC_FL_COLLAPSE_RANGE 0x08
#endif
#endif /* LINUX_DEP_H */

10
log.c
View file

@ -26,6 +26,7 @@
#include <stdarg.h>
#include <sys/socket.h>
#include "linux_dep.h"
#include "log.h"
#include "util.h"
#include "passt.h"
@ -92,7 +93,6 @@ const char *logfile_prefix[] = {
" ", /* LOG_DEBUG */
};
#ifdef FALLOC_FL_COLLAPSE_RANGE
/**
* logfile_rotate_fallocate() - Write header, set log_written after fallocate()
* @fd: Log file descriptor
@ -126,7 +126,6 @@ static void logfile_rotate_fallocate(int fd, const struct timespec *now)
log_written -= log_cut_size;
}
#endif /* FALLOC_FL_COLLAPSE_RANGE */
/**
* logfile_rotate_move() - Fallback: move recent entries toward start, then cut
@ -198,21 +197,17 @@ out:
*
* Return: 0 on success, negative error code on failure
*
* #syscalls fcntl
*
* fallocate() passed as EXTRA_SYSCALL only if FALLOC_FL_COLLAPSE_RANGE is there
* #syscalls fcntl fallocate
*/
static int logfile_rotate(int fd, const struct timespec *now)
{
if (fcntl(fd, F_SETFL, O_RDWR /* Drop O_APPEND: explicit lseek() */))
return -errno;
#ifdef FALLOC_FL_COLLAPSE_RANGE
/* Only for Linux >= 3.15, extent-based ext4 or XFS, glibc >= 2.18 */
if (!fallocate(fd, FALLOC_FL_COLLAPSE_RANGE, 0, log_cut_size))
logfile_rotate_fallocate(fd, now);
else
#endif
logfile_rotate_move(fd, now);
if (fcntl(fd, F_SETFL, O_RDWR | O_APPEND))
@ -432,4 +427,3 @@ void logfile_init(const char *name, const char *path, size_t size)
/* For FALLOC_FL_COLLAPSE_RANGE: VFS block size can be up to one page */
log_cut_size = ROUND_UP(log_size * LOGFILE_CUT_RATIO / 100, PAGE_SIZE);
}