1 files changed, 360 insertions, 0 deletions
diff --git a/hw/9pfs/codir.c b/hw/9pfs/codir.c
new file mode 100644
index 000000000..032cce04c
--- /dev/null
+++ b/hw/9pfs/codir.c
@@ -0,0 +1,360 @@
+/*
+ * 9p backend
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ *  Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+/*
+ * Not so fast! You might want to read the 9p developer docs first:
+ * https://wiki.qemu.org/Documentation/9p
+ */
+
+#include "qemu/osdep.h"
+#include "fsdev/qemu-fsdev.h"
+#include "qemu/thread.h"
+#include "qemu/coroutine.h"
+#include "qemu/main-loop.h"
+#include "coth.h"
+
+/*
+ * Intended to be called from bottom-half (e.g. background I/O thread)
+ * context.
+ */
+static int do_readdir(V9fsPDU *pdu, V9fsFidState *fidp, struct dirent **dent)
+{
+    int err = 0;
+    V9fsState *s = pdu->s;
+    struct dirent *entry;
+
+    errno = 0;
+    entry = s->ops->readdir(&s->ctx, &fidp->fs);
+    if (!entry && errno) {
+        *dent = NULL;
+        err = -errno;
+    } else {
+        *dent = entry;
+    }
+    return err;
+}
+
+/*
+ * TODO: This will be removed for performance reasons.
+ * Use v9fs_co_readdir_many() instead.
+ */
+int coroutine_fn v9fs_co_readdir(V9fsPDU *pdu, V9fsFidState *fidp,
+                                 struct dirent **dent)
+{
+    int err;
+
+    if (v9fs_request_cancelled(pdu)) {
+        return -EINTR;
+    }
+    v9fs_co_run_in_worker({
+        err = do_readdir(pdu, fidp, dent);
+    });
+    return err;
+}
+
+/*
+ * This is solely executed on a background IO thread.
+ *
+ * See v9fs_co_readdir_many() (as its only user) below for details.
+ */
+static int do_readdir_many(V9fsPDU *pdu, V9fsFidState *fidp,
+                           struct V9fsDirEnt **entries, off_t offset,
+                           int32_t maxsize, bool dostat)
+{
+    V9fsState *s = pdu->s;
+    V9fsString name;
+    int len, err = 0;
+    int32_t size = 0;
+    off_t saved_dir_pos;
+    struct dirent *dent;
+    struct V9fsDirEnt *e = NULL;
+    V9fsPath path;
+    struct stat stbuf;
+
+    *entries = NULL;
+    v9fs_path_init(&path);
+
+    /*
+     * TODO: Here should be a warn_report_once() if lock failed.
+     *
+     * With a good 9p client we should not get into concurrency here,
+     * because a good client would not use the same fid for concurrent
+     * requests. We do the lock here for safety reasons though. However
+     * the client would then suffer performance issues, so better log that
+     * issue here.
+     */
+    v9fs_readdir_lock(&fidp->fs.dir);
+
+    /* seek directory to requested initial position */
+    if (offset == 0) {
+        s->ops->rewinddir(&s->ctx, &fidp->fs);
+    } else {
+        s->ops->seekdir(&s->ctx, &fidp->fs, offset);
+    }
+
+    /* save the directory position */
+    saved_dir_pos = s->ops->telldir(&s->ctx, &fidp->fs);
+    if (saved_dir_pos < 0) {
+        err = saved_dir_pos;
+        goto out;
+    }
+
+    while (true) {
+        /* interrupt loop if request was cancelled by a Tflush request */
+        if (v9fs_request_cancelled(pdu)) {
+            err = -EINTR;
+            break;
+        }
+
+        /* get directory entry from fs driver */
+        err = do_readdir(pdu, fidp, &dent);
+        if (err || !dent) {
+            break;
+        }
+
+        /*
+         * stop this loop as soon as it would exceed the allowed maximum
+         * response message size for the directory entries collected so far,
+         * because anything beyond that size would need to be discarded by
+         * 9p controller (main thread / top half) anyway
+         */
+        v9fs_string_init(&name);
+        v9fs_string_sprintf(&name, "%s", dent->d_name);
+        len = v9fs_readdir_response_size(&name);
+        v9fs_string_free(&name);
+        if (size + len > maxsize) {
+            /* this is not an error case actually */
+            break;
+        }
+
+        /* append next node to result chain */
+        if (!e) {
+            *entries = e = g_malloc0(sizeof(V9fsDirEnt));
+        } else {
+            e = e->next = g_malloc0(sizeof(V9fsDirEnt));
+        }
+        e->dent = g_malloc0(sizeof(struct dirent));
+        memcpy(e->dent, dent, sizeof(struct dirent));
+
+        /* perform a full stat() for directory entry if requested by caller */
+        if (dostat) {
+            err = s->ops->name_to_path(
+                &s->ctx, &fidp->path, dent->d_name, &path
+            );
+            if (err < 0) {
+                err = -errno;
+                break;
+            }
+
+            err = s->ops->lstat(&s->ctx, &path, &stbuf);
+            if (err < 0) {
+                err = -errno;
+                break;
+            }
+
+            e->st = g_malloc0(sizeof(struct stat));
+            memcpy(e->st, &stbuf, sizeof(struct stat));
+        }
+
+        size += len;
+        saved_dir_pos = dent->d_off;
+    }
+
+    /* restore (last) saved position */
+    s->ops->seekdir(&s->ctx, &fidp->fs, saved_dir_pos);
+
+out:
+    v9fs_readdir_unlock(&fidp->fs.dir);
+    v9fs_path_free(&path);
+    if (err < 0) {
+        return err;
+    }
+    return size;
+}
+
+/**
+ * @brief Reads multiple directory entries in one rush.
+ *
+ * Retrieves the requested (max. amount of) directory entries from the fs
+ * driver. This function must only be called by the main IO thread (top half).
+ * Internally this function call will be dispatched to a background IO thread
+ * (bottom half) where it is eventually executed by the fs driver.
+ *
+ * @discussion Acquiring multiple directory entries in one rush from the fs
+ * driver, instead of retrieving each directory entry individually, is very
+ * beneficial from performance point of view. Because for every fs driver
+ * request latency is added, which in practice could lead to overall
+ * latencies of several hundred ms for reading all entries (of just a single
+ * directory) if every directory entry was individually requested from fs
+ * driver.
+ *
+ * @note You must @b ALWAYS call @c v9fs_free_dirents(entries) after calling
+ * v9fs_co_readdir_many(), both on success and on error cases of this
+ * function, to avoid memory leaks once @p entries are no longer needed.
+ *
+ * @param pdu - the causing 9p (T_readdir) client request
+ * @param fidp - already opened directory where readdir shall be performed on
+ * @param entries - output for directory entries (must not be NULL)
+ * @param offset - initial position inside the directory the function shall
+ *                 seek to before retrieving the directory entries
+ * @param maxsize - maximum result message body size (in bytes)
+ * @param dostat - whether a stat() should be performed and returned for
+ *                 each directory entry
+ * @returns resulting response message body size (in bytes) on success,
+ *          negative error code otherwise
+ */
+int coroutine_fn v9fs_co_readdir_many(V9fsPDU *pdu, V9fsFidState *fidp,
+                                      struct V9fsDirEnt **entries,
+                                      off_t offset, int32_t maxsize,
+                                      bool dostat)
+{
+    int err = 0;
+
+    if (v9fs_request_cancelled(pdu)) {
+        return -EINTR;
+    }
+    v9fs_co_run_in_worker({
+        err = do_readdir_many(pdu, fidp, entries, offset, maxsize, dostat);
+    });
+    return err;
+}
+
+off_t v9fs_co_telldir(V9fsPDU *pdu, V9fsFidState *fidp)
+{
+    off_t err;
+    V9fsState *s = pdu->s;
+
+    if (v9fs_request_cancelled(pdu)) {
+        return -EINTR;
+    }
+    v9fs_co_run_in_worker(
+        {
+            err = s->ops->telldir(&s->ctx, &fidp->fs);
+            if (err < 0) {
+                err = -errno;
+            }
+        });
+    return err;
+}
+
+void coroutine_fn v9fs_co_seekdir(V9fsPDU *pdu, V9fsFidState *fidp,
+                                  off_t offset)
+{
+    V9fsState *s = pdu->s;
+    if (v9fs_request_cancelled(pdu)) {
+        return;
+    }
+    v9fs_co_run_in_worker(
+        {
+            s->ops->seekdir(&s->ctx, &fidp->fs, offset);
+        });
+}
+
+void coroutine_fn v9fs_co_rewinddir(V9fsPDU *pdu, V9fsFidState *fidp)
+{
+    V9fsState *s = pdu->s;
+    if (v9fs_request_cancelled(pdu)) {
+        return;
+    }
+    v9fs_co_run_in_worker(
+        {
+            s->ops->rewinddir(&s->ctx, &fidp->fs);
+        });
+}
+
+int coroutine_fn v9fs_co_mkdir(V9fsPDU *pdu, V9fsFidState *fidp,
+                               V9fsString *name, mode_t mode, uid_t uid,
+                               gid_t gid, struct stat *stbuf)
+{
+    int err;
+    FsCred cred;
+    V9fsPath path;
+    V9fsState *s = pdu->s;
+
+    if (v9fs_request_cancelled(pdu)) {
+        return -EINTR;
+    }
+    cred_init(&cred);
+    cred.fc_mode = mode;
+    cred.fc_uid = uid;
+    cred.fc_gid = gid;
+    v9fs_path_read_lock(s);
+    v9fs_co_run_in_worker(
+        {
+            err = s->ops->mkdir(&s->ctx, &fidp->path, name->data,  &cred);
+            if (err < 0) {
+                err = -errno;
+            } else {
+                v9fs_path_init(&path);
+                err = v9fs_name_to_path(s, &fidp->path, name->data, &path);
+                if (!err) {
+                    err = s->ops->lstat(&s->ctx, &path, stbuf);
+                    if (err < 0) {
+                        err = -errno;
+                    }
+                }
+                v9fs_path_free(&path);
+            }
+        });
+    v9fs_path_unlock(s);
+    return err;
+}
+
+int coroutine_fn v9fs_co_opendir(V9fsPDU *pdu, V9fsFidState *fidp)
+{
+    int err;
+    V9fsState *s = pdu->s;
+
+    if (v9fs_request_cancelled(pdu)) {
+        return -EINTR;
+    }
+    v9fs_path_read_lock(s);
+    v9fs_co_run_in_worker(
+        {
+            err = s->ops->opendir(&s->ctx, &fidp->path, &fidp->fs);
+            if (err < 0) {
+                err = -errno;
+            } else {
+                err = 0;
+            }
+        });
+    v9fs_path_unlock(s);
+    if (!err) {
+        total_open_fd++;
+        if (total_open_fd > open_fd_hw) {
+            v9fs_reclaim_fd(pdu);
+        }
+    }
+    return err;
+}
+
+int coroutine_fn v9fs_co_closedir(V9fsPDU *pdu, V9fsFidOpenState *fs)
+{
+    int err;
+    V9fsState *s = pdu->s;
+
+    if (v9fs_request_cancelled(pdu)) {
+        return -EINTR;
+    }
+    v9fs_co_run_in_worker(
+        {
+            err = s->ops->closedir(&s->ctx, fs);
+            if (err < 0) {
+                err = -errno;
+            }
+        });
+    if (!err) {
+        total_open_fd--;
+    }
+    return err;
+}