| Message ID | 20230616152737.23545-5-bmeng@tinylab.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | net/tap: Fix QEMU frozen issue when the maximum number of file descriptors is very large | expand |
On 6/16/23 17:27, Bin Meng wrote: > This introduces a new QEMU API qemu_close_range() that closes all > open file descriptors from first to last (included). > > This API will try a more efficient call to close_range(), or walk > through of /proc/self/fd whenever these are possible, otherwise it > falls back to a plain close loop. > > Co-developed-by: Zhangjin Wu <falcon@tinylab.org> > Signed-off-by: Bin Meng <bmeng@tinylab.org> > --- > > (no changes since v1) > > include/qemu/osdep.h | 1 + > util/osdep.c | 47 ++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 48 insertions(+) > > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h > index cc61b00ba9..e22434ce10 100644 > --- a/include/qemu/osdep.h > +++ b/include/qemu/osdep.h > @@ -560,6 +560,7 @@ int qemu_open_old(const char *name, int flags, ...); > int qemu_open(const char *name, int flags, Error **errp); > int qemu_create(const char *name, int flags, mode_t mode, Error **errp); > int qemu_close(int fd); > +int qemu_close_range(unsigned int first, unsigned int last); > int qemu_unlink(const char *name); > #ifndef _WIN32 > int qemu_dup_flags(int fd, int flags); > diff --git a/util/osdep.c b/util/osdep.c > index e996c4744a..fd7dd2dbdf 100644 > --- a/util/osdep.c > +++ b/util/osdep.c > @@ -411,6 +411,53 @@ int qemu_close(int fd) > return close(fd); > } > > +int qemu_close_range(unsigned int first, unsigned int last) > +{ > + DIR *dir = NULL; > + > +#ifdef CONFIG_CLOSE_RANGE > + int r = close_range(first, last, 0); > + if (!r) { > + /* Success, no need to try other ways. */ > + return 0; > + } > +#endif > + > +#ifdef __linux__ > + dir = opendir("/proc/self/fd"); > +#endif > + if (!dir) { > + /* > + * If /proc is not mounted or /proc/self/fd is not supported, > + * try close() from first to last. > + */ > + for (int i = first; i <= last; i++) { > + close(i); > + } > + > + return 0; > + } > + > +#ifndef _WIN32 > + /* Avoid closing the directory */ > + int dfd = dirfd(dir); > + > + for (struct dirent *de = readdir(dir); de; de = readdir(dir)) { > + int fd = atoi(de->d_name); > + if (fd < first || fd > last) { > + /* Exclude the fds outside the target range */ > + continue; > + } > + if (fd != dfd) { > + close(fd); > + } > + } > + closedir(dir); > +#endif /* _WIN32 */ Poor ordering of ifdefs. #ifdef __linux__ DIR *dir = opendir("..."); if (dir) { int dfd = ... loop closedir(dir); return; } #endif since the first ifdef is the only way dir can ever be non-null. > + for (int i = first; i <= last; i++) { typeof(i) != typeof(first). r~
On 6/16/23 17:27, Bin Meng wrote: > +int qemu_close_range(unsigned int first, unsigned int last) > +{ > + DIR *dir = NULL; > + > +#ifdef CONFIG_CLOSE_RANGE > + int r = close_range(first, last, 0); > + if (!r) { > + /* Success, no need to try other ways. */ > + return 0; > + } > +#endif What about first > last? close_range will yield EINVAL, and your other fallbacks will burn lots of cpu. r~
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h index cc61b00ba9..e22434ce10 100644 --- a/include/qemu/osdep.h +++ b/include/qemu/osdep.h @@ -560,6 +560,7 @@ int qemu_open_old(const char *name, int flags, ...); int qemu_open(const char *name, int flags, Error **errp); int qemu_create(const char *name, int flags, mode_t mode, Error **errp); int qemu_close(int fd); +int qemu_close_range(unsigned int first, unsigned int last); int qemu_unlink(const char *name); #ifndef _WIN32 int qemu_dup_flags(int fd, int flags); diff --git a/util/osdep.c b/util/osdep.c index e996c4744a..fd7dd2dbdf 100644 --- a/util/osdep.c +++ b/util/osdep.c @@ -411,6 +411,53 @@ int qemu_close(int fd) return close(fd); } +int qemu_close_range(unsigned int first, unsigned int last) +{ + DIR *dir = NULL; + +#ifdef CONFIG_CLOSE_RANGE + int r = close_range(first, last, 0); + if (!r) { + /* Success, no need to try other ways. */ + return 0; + } +#endif + +#ifdef __linux__ + dir = opendir("/proc/self/fd"); +#endif + if (!dir) { + /* + * If /proc is not mounted or /proc/self/fd is not supported, + * try close() from first to last. + */ + for (int i = first; i <= last; i++) { + close(i); + } + + return 0; + } + +#ifndef _WIN32 + /* Avoid closing the directory */ + int dfd = dirfd(dir); + + for (struct dirent *de = readdir(dir); de; de = readdir(dir)) { + int fd = atoi(de->d_name); + if (fd < first || fd > last) { + /* Exclude the fds outside the target range */ + continue; + } + if (fd != dfd) { + close(fd); + } + } + closedir(dir); +#endif /* _WIN32 */ + + return 0; +} + /* * Delete a file from the filesystem, unless the filename is /dev/fdset/... *
This introduces a new QEMU API qemu_close_range() that closes all open file descriptors from first to last (included). This API will try a more efficient call to close_range(), or walk through of /proc/self/fd whenever these are possible, otherwise it falls back to a plain close loop. Co-developed-by: Zhangjin Wu <falcon@tinylab.org> Signed-off-by: Bin Meng <bmeng@tinylab.org> --- (no changes since v1) include/qemu/osdep.h | 1 + util/osdep.c | 47 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 48 insertions(+)