diff options
Diffstat (limited to 'src/libudev-queue-private.c')
| -rw-r--r-- | src/libudev-queue-private.c | 412 |
1 files changed, 412 insertions, 0 deletions
diff --git a/src/libudev-queue-private.c b/src/libudev-queue-private.c new file mode 100644 index 0000000000..e0a7b53b81 --- /dev/null +++ b/src/libudev-queue-private.c @@ -0,0 +1,412 @@ +/* + * libudev - interface to udev device information + * + * Copyright (C) 2008 Kay Sievers <kay.sievers@vrfy.org> + * Copyright (C) 2009 Alan Jenkins <alan-jenkins@tuffmail.co.uk> + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + */ + +/* + * DISCLAIMER - The file format mentioned here is private to udev/libudev, + * and may be changed without notice. + * + * The udev event queue is exported as a binary log file. + * Each log record consists of a sequence number followed by the device path. + * + * When a new event is queued, its details are appended to the log. + * When the event finishes, a second record is appended to the log + * with the same sequence number but a devpath len of 0. + * + * Example: + * { 0x0000000000000001 } + * { 0x0000000000000001, 0x0019, "/devices/virtual/mem/null" }, + * { 0x0000000000000002, 0x001b, "/devices/virtual/mem/random" }, + * { 0x0000000000000001, 0x0000 }, + * { 0x0000000000000003, 0x0019, "/devices/virtual/mem/zero" }, + * + * Events 2 and 3 are still queued, but event 1 has finished. + * + * The queue does not grow indefinitely. It is periodically re-created + * to remove finished events. Atomic rename() makes this transparent to readers. + * + * The queue file starts with a single sequence number which specifies the + * minimum sequence number in the log that follows. Any events prior to this + * sequence number have already finished. + */ + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <fcntl.h> +#include <dirent.h> +#include <limits.h> +#include <errno.h> +#include <sys/stat.h> +#include <sys/types.h> + +#include "libudev.h" +#include "libudev-private.h" + +static int rebuild_queue_file(struct udev_queue_export *udev_queue_export); + +struct udev_queue_export { + struct udev *udev; + int queued_count; /* number of unfinished events exported in queue file */ + FILE *queue_file; + unsigned long long int seqnum_max; /* earliest sequence number in queue file */ + unsigned long long int seqnum_min; /* latest sequence number in queue file */ + int waste_bytes; /* queue file bytes wasted on finished events */ +}; + +struct udev_queue_export *udev_queue_export_new(struct udev *udev) +{ + struct udev_queue_export *udev_queue_export; + unsigned long long int initial_seqnum; + + if (udev == NULL) + return NULL; + + udev_queue_export = calloc(1, sizeof(struct udev_queue_export)); + if (udev_queue_export == NULL) + return NULL; + udev_queue_export->udev = udev; + + initial_seqnum = udev_get_kernel_seqnum(udev); + udev_queue_export->seqnum_min = initial_seqnum; + udev_queue_export->seqnum_max = initial_seqnum; + + udev_queue_export_cleanup(udev_queue_export); + if (rebuild_queue_file(udev_queue_export) != 0) { + free(udev_queue_export); + return NULL; + } + + return udev_queue_export; +} + +struct udev_queue_export *udev_queue_export_unref(struct udev_queue_export *udev_queue_export) +{ + if (udev_queue_export == NULL) + return NULL; + if (udev_queue_export->queue_file != NULL) + fclose(udev_queue_export->queue_file); + free(udev_queue_export); + return NULL; +} + +void udev_queue_export_cleanup(struct udev_queue_export *udev_queue_export) +{ + char filename[UTIL_PATH_SIZE]; + + if (udev_queue_export == NULL) + return; + util_strscpyl(filename, sizeof(filename), udev_get_run_path(udev_queue_export->udev), "/queue.tmp", NULL); + unlink(filename); + util_strscpyl(filename, sizeof(filename), udev_get_run_path(udev_queue_export->udev), "/queue.bin", NULL); + unlink(filename); +} + +static int skip_to(FILE *file, long offset) +{ + long old_offset; + + /* fseek may drop buffered data, avoid it for small seeks */ + old_offset = ftell(file); + if (offset > old_offset && offset - old_offset <= BUFSIZ) { + size_t skip_bytes = offset - old_offset; + char buf[skip_bytes]; + + if (fread(buf, skip_bytes, 1, file) != skip_bytes) + return -1; + } + + return fseek(file, offset, SEEK_SET); +} + +struct queue_devpaths { + unsigned int devpaths_first; /* index of first queued event */ + unsigned int devpaths_size; + long devpaths[]; /* seqnum -> offset of devpath in queue file (or 0) */ +}; + +/* + * Returns a table mapping seqnum to devpath file offset for currently queued events. + * devpaths[i] represents the event with seqnum = i + udev_queue_export->seqnum_min. + */ +static struct queue_devpaths *build_index(struct udev_queue_export *udev_queue_export) +{ + struct queue_devpaths *devpaths; + unsigned long long int range; + long devpath_offset; + ssize_t devpath_len; + unsigned long long int seqnum; + unsigned long long int n; + unsigned int i; + + /* seek to the first event in the file */ + rewind(udev_queue_export->queue_file); + udev_queue_read_seqnum(udev_queue_export->queue_file, &seqnum); + + /* allocate the table */ + range = udev_queue_export->seqnum_min - udev_queue_export->seqnum_max; + if (range - 1 > INT_MAX) { + err(udev_queue_export->udev, "queue file overflow\n"); + return NULL; + } + devpaths = calloc(1, sizeof(struct queue_devpaths) + (range + 1) * sizeof(long)); + if (devpaths == NULL) + return NULL; + devpaths->devpaths_size = range + 1; + + /* read all records and populate the table */ + for (;;) { + if (udev_queue_read_seqnum(udev_queue_export->queue_file, &seqnum) < 0) + break; + n = seqnum - udev_queue_export->seqnum_max; + if (n >= devpaths->devpaths_size) + goto read_error; + + devpath_offset = ftell(udev_queue_export->queue_file); + devpath_len = udev_queue_skip_devpath(udev_queue_export->queue_file); + if (devpath_len < 0) + goto read_error; + + if (devpath_len > 0) + devpaths->devpaths[n] = devpath_offset; + else + devpaths->devpaths[n] = 0; + } + + /* find first queued event */ + for (i = 0; i < devpaths->devpaths_size; i++) { + if (devpaths->devpaths[i] != 0) + break; + } + devpaths->devpaths_first = i; + + return devpaths; + +read_error: + err(udev_queue_export->udev, "queue file corrupted\n"); + free(devpaths); + return NULL; +} + +static int rebuild_queue_file(struct udev_queue_export *udev_queue_export) +{ + unsigned long long int seqnum; + struct queue_devpaths *devpaths = NULL; + char filename[UTIL_PATH_SIZE]; + char filename_tmp[UTIL_PATH_SIZE]; + FILE *new_queue_file = NULL; + unsigned int i; + + /* read old queue file */ + if (udev_queue_export->queue_file != NULL) { + dbg(udev_queue_export->udev, "compacting queue file, freeing %d bytes\n", + udev_queue_export->waste_bytes); + + devpaths = build_index(udev_queue_export); + if (devpaths != NULL) + udev_queue_export->seqnum_max += devpaths->devpaths_first; + } + if (devpaths == NULL) { + dbg(udev_queue_export->udev, "creating empty queue file\n"); + udev_queue_export->queued_count = 0; + udev_queue_export->seqnum_max = udev_queue_export->seqnum_min; + } + + /* create new queue file */ + util_strscpyl(filename_tmp, sizeof(filename_tmp), udev_get_run_path(udev_queue_export->udev), "/queue.tmp", NULL); + new_queue_file = fopen(filename_tmp, "w+"); + if (new_queue_file == NULL) + goto error; + seqnum = udev_queue_export->seqnum_max; + fwrite(&seqnum, 1, sizeof(unsigned long long int), new_queue_file); + + /* copy unfinished events only to the new file */ + if (devpaths != NULL) { + for (i = devpaths->devpaths_first; i < devpaths->devpaths_size; i++) { + char devpath[UTIL_PATH_SIZE]; + int err; + unsigned short devpath_len; + + if (devpaths->devpaths[i] != 0) + { + skip_to(udev_queue_export->queue_file, devpaths->devpaths[i]); + err = udev_queue_read_devpath(udev_queue_export->queue_file, devpath, sizeof(devpath)); + devpath_len = err; + + fwrite(&seqnum, sizeof(unsigned long long int), 1, new_queue_file); + fwrite(&devpath_len, sizeof(unsigned short), 1, new_queue_file); + fwrite(devpath, 1, devpath_len, new_queue_file); + } + seqnum++; + } + free(devpaths); + devpaths = NULL; + } + fflush(new_queue_file); + if (ferror(new_queue_file)) + goto error; + + /* rename the new file on top of the old one */ + util_strscpyl(filename, sizeof(filename), udev_get_run_path(udev_queue_export->udev), "/queue.bin", NULL); + if (rename(filename_tmp, filename) != 0) + goto error; + + if (udev_queue_export->queue_file != NULL) + fclose(udev_queue_export->queue_file); + udev_queue_export->queue_file = new_queue_file; + udev_queue_export->waste_bytes = 0; + + return 0; + +error: + err(udev_queue_export->udev, "failed to create queue file: %m\n"); + udev_queue_export_cleanup(udev_queue_export); + + if (udev_queue_export->queue_file != NULL) { + fclose(udev_queue_export->queue_file); + udev_queue_export->queue_file = NULL; + } + if (new_queue_file != NULL) + fclose(new_queue_file); + + if (devpaths != NULL) + free(devpaths); + udev_queue_export->queued_count = 0; + udev_queue_export->waste_bytes = 0; + udev_queue_export->seqnum_max = udev_queue_export->seqnum_min; + + return -1; +} + +static int write_queue_record(struct udev_queue_export *udev_queue_export, + unsigned long long int seqnum, const char *devpath, size_t devpath_len) +{ + unsigned short len; + + if (udev_queue_export->queue_file == NULL) { + dbg(udev_queue_export->udev, "can't record event: queue file not available\n"); + return -1; + } + + if (fwrite(&seqnum, sizeof(unsigned long long int), 1, udev_queue_export->queue_file) != 1) + goto write_error; + + len = (devpath_len < USHRT_MAX) ? devpath_len : USHRT_MAX; + if (fwrite(&len, sizeof(unsigned short), 1, udev_queue_export->queue_file) != 1) + goto write_error; + if (len > 0) { + if (fwrite(devpath, 1, len, udev_queue_export->queue_file) != len) + goto write_error; + } + + /* *must* flush output; caller may fork */ + if (fflush(udev_queue_export->queue_file) != 0) + goto write_error; + + return 0; + +write_error: + /* if we failed half way through writing a record to a file, + we should not try to write any further records to it. */ + err(udev_queue_export->udev, "error writing to queue file: %m\n"); + fclose(udev_queue_export->queue_file); + udev_queue_export->queue_file = NULL; + + return -1; +} + +enum device_state { + DEVICE_QUEUED, + DEVICE_FINISHED, +}; + +static inline size_t queue_record_size(size_t devpath_len) +{ + return sizeof(unsigned long long int) + sizeof(unsigned short int) + devpath_len; +} + +static int update_queue(struct udev_queue_export *udev_queue_export, + struct udev_device *udev_device, enum device_state state) +{ + unsigned long long int seqnum = udev_device_get_seqnum(udev_device); + const char *devpath = NULL; + size_t devpath_len = 0; + int bytes; + int err; + + /* FINISHED records have a zero length devpath */ + if (state == DEVICE_QUEUED) { + devpath = udev_device_get_devpath(udev_device); + devpath_len = strlen(devpath); + } + + /* recover from an earlier failed rebuild */ + if (udev_queue_export->queue_file == NULL) { + if (rebuild_queue_file(udev_queue_export) != 0) + return -1; + } + + /* if we're removing the last event from the queue, that's the best time to rebuild it */ + if (state != DEVICE_QUEUED && udev_queue_export->queued_count == 1) { + /* we don't need to read the old queue file */ + fclose(udev_queue_export->queue_file); + udev_queue_export->queue_file = NULL; + rebuild_queue_file(udev_queue_export); + return 0; + } + + /* try to rebuild the queue files before they grow larger than one page. */ + bytes = ftell(udev_queue_export->queue_file) + queue_record_size(devpath_len); + if ((udev_queue_export->waste_bytes > bytes / 2) && bytes > 4096) + rebuild_queue_file(udev_queue_export); + + /* don't record a finished event, if we already dropped the event in a failed rebuild */ + if (seqnum < udev_queue_export->seqnum_max) + return 0; + + /* now write to the queue */ + if (state == DEVICE_QUEUED) { + udev_queue_export->queued_count++; + udev_queue_export->seqnum_min = seqnum; + } else { + udev_queue_export->waste_bytes += queue_record_size(devpath_len) + queue_record_size(0); + udev_queue_export->queued_count--; + } + err = write_queue_record(udev_queue_export, seqnum, devpath, devpath_len); + + /* try to handle ENOSPC */ + if (err != 0 && udev_queue_export->queued_count == 0) { + udev_queue_export_cleanup(udev_queue_export); + err = rebuild_queue_file(udev_queue_export); + } + + return err; +} + +static int update(struct udev_queue_export *udev_queue_export, + struct udev_device *udev_device, enum device_state state) +{ + if (update_queue(udev_queue_export, udev_device, state) != 0) + return -1; + + return 0; +} + +int udev_queue_export_device_queued(struct udev_queue_export *udev_queue_export, struct udev_device *udev_device) +{ + return update(udev_queue_export, udev_device, DEVICE_QUEUED); +} + +int udev_queue_export_device_finished(struct udev_queue_export *udev_queue_export, struct udev_device *udev_device) +{ + return update(udev_queue_export, udev_device, DEVICE_FINISHED); +} |