fsmonitor: refactor initialization of fsmonitor_last_update token

[alt-git.git] / fsmonitor.c

#include "cache.h"
#include "config.h"
#include "dir.h"
#include "ewah/ewok.h"
#include "fsmonitor.h"
#include "run-command.h"
#include "strbuf.h"

#define INDEX_EXTENSION_VERSION1        (1)
#define INDEX_EXTENSION_VERSION2        (2)
#define HOOK_INTERFACE_VERSION1         (1)
#define HOOK_INTERFACE_VERSION2         (2)

struct trace_key trace_fsmonitor = TRACE_KEY_INIT(FSMONITOR);

static void fsmonitor_ewah_callback(size_t pos, void *is)
{
        struct index_state *istate = (struct index_state *)is;
        struct cache_entry *ce;

        if (pos >= istate->cache_nr)
                BUG("fsmonitor_dirty has more entries than the index (%"PRIuMAX" >= %u)",
                    (uintmax_t)pos, istate->cache_nr);

        ce = istate->cache[pos];
        ce->ce_flags &= ~CE_FSMONITOR_VALID;
}

static int fsmonitor_hook_version(void)
{
        int hook_version;

        if (git_config_get_int("core.fsmonitorhookversion", &hook_version))
                return -1;

        if (hook_version == HOOK_INTERFACE_VERSION1 ||
            hook_version == HOOK_INTERFACE_VERSION2)
                return hook_version;

        warning("Invalid hook version '%i' in core.fsmonitorhookversion. "
                "Must be 1 or 2.", hook_version);
        return -1;
}

int read_fsmonitor_extension(struct index_state *istate, const void *data,
        unsigned long sz)
{
        const char *index = data;
        uint32_t hdr_version;
        uint32_t ewah_size;
        struct ewah_bitmap *fsmonitor_dirty;
        int ret;
        uint64_t timestamp;
        struct strbuf last_update = STRBUF_INIT;

        if (sz < sizeof(uint32_t) + 1 + sizeof(uint32_t))
                return error("corrupt fsmonitor extension (too short)");

        hdr_version = get_be32(index);
        index += sizeof(uint32_t);
        if (hdr_version == INDEX_EXTENSION_VERSION1) {
                timestamp = get_be64(index);
                strbuf_addf(&last_update, "%"PRIu64"", timestamp);
                index += sizeof(uint64_t);
        } else if (hdr_version == INDEX_EXTENSION_VERSION2) {
                strbuf_addstr(&last_update, index);
                index += last_update.len + 1;
        } else {
                return error("bad fsmonitor version %d", hdr_version);
        }

        istate->fsmonitor_last_update = strbuf_detach(&last_update, NULL);

        ewah_size = get_be32(index);
        index += sizeof(uint32_t);

        fsmonitor_dirty = ewah_new();
        ret = ewah_read_mmap(fsmonitor_dirty, index, ewah_size);
        if (ret != ewah_size) {
                ewah_free(fsmonitor_dirty);
                return error("failed to parse ewah bitmap reading fsmonitor index extension");
        }
        istate->fsmonitor_dirty = fsmonitor_dirty;

        if (!istate->split_index &&
            istate->fsmonitor_dirty->bit_size > istate->cache_nr)
                BUG("fsmonitor_dirty has more entries than the index (%"PRIuMAX" > %u)",
                    (uintmax_t)istate->fsmonitor_dirty->bit_size, istate->cache_nr);

        trace2_data_string("index", NULL, "extension/fsmn/read/token",
                           istate->fsmonitor_last_update);
        trace_printf_key(&trace_fsmonitor,
                         "read fsmonitor extension successful '%s'",
                         istate->fsmonitor_last_update);
        return 0;
}

void fill_fsmonitor_bitmap(struct index_state *istate)
{
        unsigned int i, skipped = 0;
        istate->fsmonitor_dirty = ewah_new();
        for (i = 0; i < istate->cache_nr; i++) {
                if (istate->cache[i]->ce_flags & CE_REMOVE)
                        skipped++;
                else if (!(istate->cache[i]->ce_flags & CE_FSMONITOR_VALID))
                        ewah_set(istate->fsmonitor_dirty, i - skipped);
        }
}

void write_fsmonitor_extension(struct strbuf *sb, struct index_state *istate)
{
        uint32_t hdr_version;
        uint32_t ewah_start;
        uint32_t ewah_size = 0;
        int fixup = 0;

        if (!istate->split_index &&
            istate->fsmonitor_dirty->bit_size > istate->cache_nr)
                BUG("fsmonitor_dirty has more entries than the index (%"PRIuMAX" > %u)",
                    (uintmax_t)istate->fsmonitor_dirty->bit_size, istate->cache_nr);

        put_be32(&hdr_version, INDEX_EXTENSION_VERSION2);
        strbuf_add(sb, &hdr_version, sizeof(uint32_t));

        strbuf_addstr(sb, istate->fsmonitor_last_update);
        strbuf_addch(sb, 0); /* Want to keep a NUL */

        fixup = sb->len;
        strbuf_add(sb, &ewah_size, sizeof(uint32_t)); /* we'll fix this up later */

        ewah_start = sb->len;
        ewah_serialize_strbuf(istate->fsmonitor_dirty, sb);
        ewah_free(istate->fsmonitor_dirty);
        istate->fsmonitor_dirty = NULL;

        /* fix up size field */
        put_be32(&ewah_size, sb->len - ewah_start);
        memcpy(sb->buf + fixup, &ewah_size, sizeof(uint32_t));

        trace2_data_string("index", NULL, "extension/fsmn/write/token",
                           istate->fsmonitor_last_update);
        trace_printf_key(&trace_fsmonitor,
                         "write fsmonitor extension successful '%s'",
                         istate->fsmonitor_last_update);
}

/*
 * Call the query-fsmonitor hook passing the last update token of the saved results.
 */
static int query_fsmonitor(int version, const char *last_update, struct strbuf *query_result)
{
        struct child_process cp = CHILD_PROCESS_INIT;
        int result;

        if (!core_fsmonitor)
                return -1;

        strvec_push(&cp.args, core_fsmonitor);
        strvec_pushf(&cp.args, "%d", version);
        strvec_pushf(&cp.args, "%s", last_update);
        cp.use_shell = 1;
        cp.dir = get_git_work_tree();

        trace2_region_enter("fsm_hook", "query", NULL);

        result = capture_command(&cp, query_result, 1024);

        if (result)
                trace2_data_intmax("fsm_hook", NULL, "query/failed", result);
        else {
                trace2_data_intmax("fsm_hook", NULL, "query/response-length",
                                   query_result->len);

                if (fsmonitor_is_trivial_response(query_result))
                        trace2_data_intmax("fsm_hook", NULL,
                                           "query/trivial-response", 1);
        }

        trace2_region_leave("fsm_hook", "query", NULL);

        return result;
}

int fsmonitor_is_trivial_response(const struct strbuf *query_result)
{
        static char trivial_response[3] = { '\0', '/', '\0' };
        int is_trivial = !memcmp(trivial_response,
                                 &query_result->buf[query_result->len - 3], 3);

        return is_trivial;
}

static void fsmonitor_refresh_callback(struct index_state *istate, char *name)
{
        int i, len = strlen(name);
        if (name[len - 1] == '/') {

                /*
                 * TODO We should binary search to find the first path with
                 * TODO this directory prefix.  Then linearly update entries
                 * TODO while the prefix matches.  Taking care to search without
                 * TODO the trailing slash -- because '/' sorts after a few
                 * TODO interesting special chars, like '.' and ' '.
                 */

                /* Mark all entries for the folder invalid */
                for (i = 0; i < istate->cache_nr; i++) {
                        if (istate->cache[i]->ce_flags & CE_FSMONITOR_VALID &&
                            starts_with(istate->cache[i]->name, name))
                                istate->cache[i]->ce_flags &= ~CE_FSMONITOR_VALID;
                }
                /* Need to remove the / from the path for the untracked cache */
                name[len - 1] = '\0';
        } else {
                int pos = index_name_pos(istate, name, strlen(name));

                if (pos >= 0) {
                        struct cache_entry *ce = istate->cache[pos];
                        ce->ce_flags &= ~CE_FSMONITOR_VALID;
                }
        }

        /*
         * Mark the untracked cache dirty even if it wasn't found in the index
         * as it could be a new untracked file.
         */
        trace_printf_key(&trace_fsmonitor, "fsmonitor_refresh_callback '%s'", name);
        untracked_cache_invalidate_path(istate, name, 0);
}

void refresh_fsmonitor(struct index_state *istate)
{
        struct strbuf query_result = STRBUF_INIT;
        int query_success = 0, hook_version = -1;
        size_t bol = 0; /* beginning of line */
        uint64_t last_update;
        struct strbuf last_update_token = STRBUF_INIT;
        char *buf;
        unsigned int i;

        if (!core_fsmonitor || istate->fsmonitor_has_run_once)
                return;

        hook_version = fsmonitor_hook_version();

        istate->fsmonitor_has_run_once = 1;

        trace_printf_key(&trace_fsmonitor, "refresh fsmonitor");
        /*
         * This could be racy so save the date/time now and query_fsmonitor
         * should be inclusive to ensure we don't miss potential changes.
         */
        last_update = getnanotime();
        if (hook_version == HOOK_INTERFACE_VERSION1)
                strbuf_addf(&last_update_token, "%"PRIu64"", last_update);

        /*
         * If we have a last update token, call query_fsmonitor for the set of
         * changes since that token, else assume everything is possibly dirty
         * and check it all.
         */
        if (istate->fsmonitor_last_update) {
                if (hook_version == -1 || hook_version == HOOK_INTERFACE_VERSION2) {
                        query_success = !query_fsmonitor(HOOK_INTERFACE_VERSION2,
                                istate->fsmonitor_last_update, &query_result);

                        if (query_success) {
                                if (hook_version < 0)
                                        hook_version = HOOK_INTERFACE_VERSION2;

                                /*
                                 * First entry will be the last update token
                                 * Need to use a char * variable because static
                                 * analysis was suggesting to use strbuf_addbuf
                                 * but we don't want to copy the entire strbuf
                                 * only the chars up to the first NUL
                                 */
                                buf = query_result.buf;
                                strbuf_addstr(&last_update_token, buf);
                                if (!last_update_token.len) {
                                        warning("Empty last update token.");
                                        query_success = 0;
                                } else {
                                        bol = last_update_token.len + 1;
                                }
                        } else if (hook_version < 0) {
                                hook_version = HOOK_INTERFACE_VERSION1;
                                if (!last_update_token.len)
                                        strbuf_addf(&last_update_token, "%"PRIu64"", last_update);
                        }
                }

                if (hook_version == HOOK_INTERFACE_VERSION1) {
                        query_success = !query_fsmonitor(HOOK_INTERFACE_VERSION1,
                                istate->fsmonitor_last_update, &query_result);
                }

                trace_performance_since(last_update, "fsmonitor process '%s'", core_fsmonitor);
                trace_printf_key(&trace_fsmonitor, "fsmonitor process '%s' returned %s",
                        core_fsmonitor, query_success ? "success" : "failure");
        }

        /* a fsmonitor process can return '/' to indicate all entries are invalid */
        if (query_success && query_result.buf[bol] != '/') {
                /* Mark all entries returned by the monitor as dirty */
                buf = query_result.buf;
                for (i = bol; i < query_result.len; i++) {
                        if (buf[i] != '\0')
                                continue;
                        fsmonitor_refresh_callback(istate, buf + bol);
                        bol = i + 1;
                }
                if (bol < query_result.len)
                        fsmonitor_refresh_callback(istate, buf + bol);

                /* Now mark the untracked cache for fsmonitor usage */
                if (istate->untracked)
                        istate->untracked->use_fsmonitor = 1;
        } else {

                /* We only want to run the post index changed hook if we've actually changed entries, so keep track
                 * if we actually changed entries or not */
                int is_cache_changed = 0;
                /* Mark all entries invalid */
                for (i = 0; i < istate->cache_nr; i++) {
                        if (istate->cache[i]->ce_flags & CE_FSMONITOR_VALID) {
                                is_cache_changed = 1;
                                istate->cache[i]->ce_flags &= ~CE_FSMONITOR_VALID;
                        }
                }

                /* If we're going to check every file, ensure we save the results */
                if (is_cache_changed)
                        istate->cache_changed |= FSMONITOR_CHANGED;

                if (istate->untracked)
                        istate->untracked->use_fsmonitor = 0;
        }
        strbuf_release(&query_result);

        /* Now that we've updated istate, save the last_update_token */
        FREE_AND_NULL(istate->fsmonitor_last_update);
        istate->fsmonitor_last_update = strbuf_detach(&last_update_token, NULL);
}

/*
 * The caller wants to turn on FSMonitor.  And when the caller writes
 * the index to disk, a FSMonitor extension should be included.  This
 * requires that `istate->fsmonitor_last_update` not be NULL.  But we
 * have not actually talked to a FSMonitor process yet, so we don't
 * have an initial value for this field.
 *
 * For a protocol V1 FSMonitor process, this field is a formatted
 * "nanoseconds since epoch" field.  However, for a protocol V2
 * FSMonitor process, this field is an opaque token.
 *
 * Historically, `add_fsmonitor()` has initialized this field to the
 * current time for protocol V1 processes.  There are lots of race
 * conditions here, but that code has shipped...
 *
 * The only true solution is to use a V2 FSMonitor and get a current
 * or default token value (that it understands), but we cannot do that
 * until we have actually talked to an instance of the FSMonitor process
 * (but the protocol requires that we send a token first...).
 *
 * For simplicity, just initialize like we have a V1 process and require
 * that V2 processes adapt.
 */
static void initialize_fsmonitor_last_update(struct index_state *istate)
{
        struct strbuf last_update = STRBUF_INIT;

        strbuf_addf(&last_update, "%"PRIu64"", getnanotime());
        istate->fsmonitor_last_update = strbuf_detach(&last_update, NULL);
}

void add_fsmonitor(struct index_state *istate)
{
        unsigned int i;

        if (!istate->fsmonitor_last_update) {
                trace_printf_key(&trace_fsmonitor, "add fsmonitor");
                istate->cache_changed |= FSMONITOR_CHANGED;
                initialize_fsmonitor_last_update(istate);

                /* reset the fsmonitor state */
                for (i = 0; i < istate->cache_nr; i++)
                        istate->cache[i]->ce_flags &= ~CE_FSMONITOR_VALID;

                /* reset the untracked cache */
                if (istate->untracked) {
                        add_untracked_cache(istate);
                        istate->untracked->use_fsmonitor = 1;
                }

                /* Update the fsmonitor state */
                refresh_fsmonitor(istate);
        }
}

void remove_fsmonitor(struct index_state *istate)
{
        if (istate->fsmonitor_last_update) {
                trace_printf_key(&trace_fsmonitor, "remove fsmonitor");
                istate->cache_changed |= FSMONITOR_CHANGED;
                FREE_AND_NULL(istate->fsmonitor_last_update);
        }
}

void tweak_fsmonitor(struct index_state *istate)
{
        unsigned int i;
        int fsmonitor_enabled = git_config_get_fsmonitor();

        if (istate->fsmonitor_dirty) {
                if (fsmonitor_enabled) {
                        /* Mark all entries valid */
                        for (i = 0; i < istate->cache_nr; i++) {
                                istate->cache[i]->ce_flags |= CE_FSMONITOR_VALID;
                        }

                        /* Mark all previously saved entries as dirty */
                        if (istate->fsmonitor_dirty->bit_size > istate->cache_nr)
                                BUG("fsmonitor_dirty has more entries than the index (%"PRIuMAX" > %u)",
                                    (uintmax_t)istate->fsmonitor_dirty->bit_size, istate->cache_nr);
                        ewah_each_bit(istate->fsmonitor_dirty, fsmonitor_ewah_callback, istate);

                        refresh_fsmonitor(istate);
                }

                ewah_free(istate->fsmonitor_dirty);
                istate->fsmonitor_dirty = NULL;
        }

        switch (fsmonitor_enabled) {
        case -1: /* keep: do nothing */
                break;
        case 0: /* false */
                remove_fsmonitor(istate);
                break;
        case 1: /* true */
                add_fsmonitor(istate);
                break;
        default: /* unknown value: do nothing */
                break;
        }
}