| Message ID | 20240731084832.1829291-5-cleger@rivosinc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | qemu/osdep: add a qemu_close_all_open_fd() helper | expand |
On 7/31/24 18:48, Clément Léger wrote: > @@ -823,8 +824,34 @@ static bool qemu_close_all_open_fd_proc(void) > dfd = dirfd(dir); > > for (de = readdir(dir); de; de = readdir(dir)) { > + bool close_fd = true; > + > + if (de->d_name[0] == '.') { > + continue; > + } > fd = atoi(de->d_name); > - if (fd != dfd) { > + if (fd == dfd) { > + close_fd = false; > + continue; > + } Assignment to close_fd not used here. > + > + for (unsigned int i = skip_start; i < skip_end; i++) { > + if (fd < skip[i]) { > + /* We are below the next skipped fd, break */ > + break; > + } else if (fd == skip[i]) { > + close_fd = false; > + /* Restrict the range as we found fds matching start/end */ > + if (i == skip_start) { > + skip_start++; > + } else if (i == skip_end) { > + skip_end--; > + } > + break; > + } > + } > + > + if (close_fd) { > close(fd); > } > } > @@ -833,24 +860,68 @@ static bool qemu_close_all_open_fd_proc(void) > return true; > } > > -static bool qemu_close_all_open_fd_close_range(void) > +static bool qemu_close_all_open_fd_close_range(const int *skip, > + unsigned int nskip, > + int open_max) > { > #ifdef CONFIG_CLOSE_RANGE > - int r = close_range(0, ~0U, 0); > - if (!r) { > - /* Success, no need to try other ways. */ > - return true; > - } > -#endif > + int first = 0, last = open_max; If this were really _SC_OPEN_MAX, this would be off-by-one. > -static void qemu_close_all_open_fd_fallback(void) > +static void qemu_close_all_open_fd_fallback(const int *skip, unsigned int nskip, > + int open_max) > { > - int open_max = sysconf(_SC_OPEN_MAX), i; > + unsigned int cur_skip = 0; > > /* Fallback */ > - for (i = 0; i < open_max; i++) { > + for (int i = 0; i < open_max; i++) { Because this isn't really _SC_OPEN_MAX, this *is* off-by-one. > -void qemu_close_all_open_fd(void) > +void qemu_close_all_open_fd(const int *skip, unsigned int nskip) > { > - if (!qemu_close_all_open_fd_close_range() && > - !qemu_close_all_open_fd_proc()) { > - qemu_close_all_open_fd_fallback(); > + int open_max = sysconf(_SC_OPEN_MAX) - 1; Better to move the -1 into qemu_close_all_open_fd_close_range where it's actually needed. r~
On 31/07/2024 23:56, Richard Henderson wrote: > On 7/31/24 18:48, Clément Léger wrote: >> @@ -823,8 +824,34 @@ static bool qemu_close_all_open_fd_proc(void) >> dfd = dirfd(dir); >> for (de = readdir(dir); de; de = readdir(dir)) { >> + bool close_fd = true; >> + >> + if (de->d_name[0] == '.') { >> + continue; >> + } >> fd = atoi(de->d_name); >> - if (fd != dfd) { >> + if (fd == dfd) { >> + close_fd = false; >> + continue; >> + } > > Assignment to close_fd not used here. > >> + >> + for (unsigned int i = skip_start; i < skip_end; i++) { >> + if (fd < skip[i]) { >> + /* We are below the next skipped fd, break */ >> + break; >> + } else if (fd == skip[i]) { >> + close_fd = false; >> + /* Restrict the range as we found fds matching >> start/end */ >> + if (i == skip_start) { >> + skip_start++; >> + } else if (i == skip_end) { >> + skip_end--; >> + } >> + break; >> + } >> + } >> + >> + if (close_fd) { >> close(fd); >> } >> } >> @@ -833,24 +860,68 @@ static bool qemu_close_all_open_fd_proc(void) >> return true; >> } >> -static bool qemu_close_all_open_fd_close_range(void) >> +static bool qemu_close_all_open_fd_close_range(const int *skip, >> + unsigned int nskip, >> + int open_max) >> { >> #ifdef CONFIG_CLOSE_RANGE >> - int r = close_range(0, ~0U, 0); >> - if (!r) { >> - /* Success, no need to try other ways. */ >> - return true; >> - } >> -#endif >> + int first = 0, last = open_max; > > If this were really _SC_OPEN_MAX, this would be off-by-one. > >> -static void qemu_close_all_open_fd_fallback(void) >> +static void qemu_close_all_open_fd_fallback(const int *skip, unsigned >> int nskip, >> + int open_max) >> { >> - int open_max = sysconf(_SC_OPEN_MAX), i; >> + unsigned int cur_skip = 0; >> /* Fallback */ >> - for (i = 0; i < open_max; i++) { >> + for (int i = 0; i < open_max; i++) { > > Because this isn't really _SC_OPEN_MAX, this *is* off-by-one. > >> -void qemu_close_all_open_fd(void) >> +void qemu_close_all_open_fd(const int *skip, unsigned int nskip) >> { >> - if (!qemu_close_all_open_fd_close_range() && >> - !qemu_close_all_open_fd_proc()) { >> - qemu_close_all_open_fd_fallback(); >> + int open_max = sysconf(_SC_OPEN_MAX) - 1; > > Better to move the -1 into qemu_close_all_open_fd_close_range where it's > actually needed. Arg, I had it right in the previous version but messed up with the SC_OPEN_MAX factorization. I'll fix that, Thanks, CLément > > > r~
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h index 5cd8517380..0bf6f0a356 100644 --- a/include/qemu/osdep.h +++ b/include/qemu/osdep.h @@ -760,9 +760,13 @@ int qemu_fdatasync(int fd); /** * qemu_close_all_open_fd: * - * Close all open file descriptors + * Close all open file descriptors except the ones supplied in the @skip array + * + * @skip: ordered array of distinct file descriptors that should not be closed + * if any, or NULL. + * @nskip: number of entries in the @skip array or 0 if @skip is NULL. */ -void qemu_close_all_open_fd(void); +void qemu_close_all_open_fd(const int *skip, unsigned int nskip); /** * Sync changes made to the memory mapped file back to the backing diff --git a/system/async-teardown.c b/system/async-teardown.c index edf49e1007..9148ee8d04 100644 --- a/system/async-teardown.c +++ b/system/async-teardown.c @@ -52,7 +52,7 @@ static int async_teardown_fn(void *arg) * Close all file descriptors that might have been inherited from the * main qemu process when doing clone, needed to make libvirt happy. */ - qemu_close_all_open_fd(); + qemu_close_all_open_fd(NULL, 0); /* Set up a handler for SIGHUP and unblock SIGHUP. */ sigaction(SIGHUP, &sa, NULL); diff --git a/util/oslib-posix.c b/util/oslib-posix.c index 9b79fc7cff..7583192192 100644 --- a/util/oslib-posix.c +++ b/util/oslib-posix.c @@ -808,11 +808,12 @@ int qemu_msync(void *addr, size_t length, int fd) return msync(addr, length, MS_SYNC); } -static bool qemu_close_all_open_fd_proc(void) +static bool qemu_close_all_open_fd_proc(const int *skip, unsigned int nskip) { struct dirent *de; int fd, dfd; DIR *dir; + unsigned int skip_start = 0, skip_end = nskip; dir = opendir("/proc/self/fd"); if (!dir) { @@ -823,8 +824,34 @@ static bool qemu_close_all_open_fd_proc(void) dfd = dirfd(dir); for (de = readdir(dir); de; de = readdir(dir)) { + bool close_fd = true; + + if (de->d_name[0] == '.') { + continue; + } fd = atoi(de->d_name); - if (fd != dfd) { + if (fd == dfd) { + close_fd = false; + continue; + } + + for (unsigned int i = skip_start; i < skip_end; i++) { + if (fd < skip[i]) { + /* We are below the next skipped fd, break */ + break; + } else if (fd == skip[i]) { + close_fd = false; + /* Restrict the range as we found fds matching start/end */ + if (i == skip_start) { + skip_start++; + } else if (i == skip_end) { + skip_end--; + } + break; + } + } + + if (close_fd) { close(fd); } } @@ -833,24 +860,68 @@ static bool qemu_close_all_open_fd_proc(void) return true; } -static bool qemu_close_all_open_fd_close_range(void) +static bool qemu_close_all_open_fd_close_range(const int *skip, + unsigned int nskip, + int open_max) { #ifdef CONFIG_CLOSE_RANGE - int r = close_range(0, ~0U, 0); - if (!r) { - /* Success, no need to try other ways. */ - return true; - } -#endif + int first = 0, last = open_max; + unsigned int cur_skip = 0; + int ret; + + do { + /* Find the start boundary of the range to close */ + while (cur_skip < nskip && first == skip[cur_skip]) { + cur_skip++; + first++; + } + + /* Find the upper boundary of the range to close */ + if (cur_skip < nskip) { + last = skip[cur_skip] - 1; + } + /* + * Adjust the maximum fd to close if it's above what the system + * supports + */ + if (last > open_max) { + last = open_max; + /* + * We can directly skip the remaining skip fds since the current + * one is already above the maximum supported one. + */ + cur_skip = nskip; + } + /* If last was adjusted, we might be > first, bail out */ + if (first > last) { + break; + } + + ret = close_range(first, last, 0); + if (ret < 0) { + return false; + } + first = last + 1; + last = open_max; + } while (cur_skip < nskip); + + return true; +#else return false; +#endif } -static void qemu_close_all_open_fd_fallback(void) +static void qemu_close_all_open_fd_fallback(const int *skip, unsigned int nskip, + int open_max) { - int open_max = sysconf(_SC_OPEN_MAX), i; + unsigned int cur_skip = 0; /* Fallback */ - for (i = 0; i < open_max; i++) { + for (int i = 0; i < open_max; i++) { + if (cur_skip < nskip && i == skip[cur_skip]) { + cur_skip++; + continue; + } close(i); } } @@ -858,10 +929,14 @@ static void qemu_close_all_open_fd_fallback(void) /* * Close all open file descriptors. */ -void qemu_close_all_open_fd(void) +void qemu_close_all_open_fd(const int *skip, unsigned int nskip) { - if (!qemu_close_all_open_fd_close_range() && - !qemu_close_all_open_fd_proc()) { - qemu_close_all_open_fd_fallback(); + int open_max = sysconf(_SC_OPEN_MAX) - 1; + + assert(skip != NULL || nskip == 0); + + if (!qemu_close_all_open_fd_close_range(skip, nskip, open_max) && + !qemu_close_all_open_fd_proc(skip, nskip)) { + qemu_close_all_open_fd_fallback(skip, nskip, open_max); } }
In order for this function to be usable by tap.c code, add a list of file descriptors that should not be closed. Signed-off-by: Clément Léger <cleger@rivosinc.com> --- include/qemu/osdep.h | 8 ++- system/async-teardown.c | 2 +- util/oslib-posix.c | 107 ++++++++++++++++++++++++++++++++++------ 3 files changed, 98 insertions(+), 19 deletions(-)