6f56908427
To lower the entry level for new developers, add a link to the 9p developer docs (i.e. qemu wiki) to MAINTAINERS and to the beginning of 9p source files, that is to: https://wiki.qemu.org/Documentation/9p Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com> Acked-by: Greg Kurz <groug@kaod.org> Message-Id: <E1leeDf-0008GZ-9q@lizzy.crudebyte.com>
361 lines
9.9 KiB
C
361 lines
9.9 KiB
C
/*
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* 9p backend
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*
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* Copyright IBM, Corp. 2011
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*
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* Authors:
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* Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*
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*/
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/*
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* Not so fast! You might want to read the 9p developer docs first:
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* https://wiki.qemu.org/Documentation/9p
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*/
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#include "qemu/osdep.h"
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#include "fsdev/qemu-fsdev.h"
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#include "qemu/thread.h"
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#include "qemu/coroutine.h"
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#include "qemu/main-loop.h"
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#include "coth.h"
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/*
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* Intended to be called from bottom-half (e.g. background I/O thread)
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* context.
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*/
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static int do_readdir(V9fsPDU *pdu, V9fsFidState *fidp, struct dirent **dent)
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{
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int err = 0;
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V9fsState *s = pdu->s;
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struct dirent *entry;
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errno = 0;
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entry = s->ops->readdir(&s->ctx, &fidp->fs);
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if (!entry && errno) {
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*dent = NULL;
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err = -errno;
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} else {
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*dent = entry;
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}
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return err;
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}
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/*
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* TODO: This will be removed for performance reasons.
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* Use v9fs_co_readdir_many() instead.
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*/
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int coroutine_fn v9fs_co_readdir(V9fsPDU *pdu, V9fsFidState *fidp,
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struct dirent **dent)
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{
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int err;
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if (v9fs_request_cancelled(pdu)) {
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return -EINTR;
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}
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v9fs_co_run_in_worker({
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err = do_readdir(pdu, fidp, dent);
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});
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return err;
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}
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/*
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* This is solely executed on a background IO thread.
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*
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* See v9fs_co_readdir_many() (as its only user) below for details.
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*/
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static int do_readdir_many(V9fsPDU *pdu, V9fsFidState *fidp,
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struct V9fsDirEnt **entries, off_t offset,
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int32_t maxsize, bool dostat)
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{
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V9fsState *s = pdu->s;
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V9fsString name;
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int len, err = 0;
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int32_t size = 0;
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off_t saved_dir_pos;
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struct dirent *dent;
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struct V9fsDirEnt *e = NULL;
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V9fsPath path;
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struct stat stbuf;
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*entries = NULL;
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v9fs_path_init(&path);
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/*
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* TODO: Here should be a warn_report_once() if lock failed.
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*
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* With a good 9p client we should not get into concurrency here,
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* because a good client would not use the same fid for concurrent
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* requests. We do the lock here for safety reasons though. However
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* the client would then suffer performance issues, so better log that
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* issue here.
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*/
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v9fs_readdir_lock(&fidp->fs.dir);
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/* seek directory to requested initial position */
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if (offset == 0) {
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s->ops->rewinddir(&s->ctx, &fidp->fs);
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} else {
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s->ops->seekdir(&s->ctx, &fidp->fs, offset);
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}
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/* save the directory position */
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saved_dir_pos = s->ops->telldir(&s->ctx, &fidp->fs);
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if (saved_dir_pos < 0) {
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err = saved_dir_pos;
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goto out;
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}
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while (true) {
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/* interrupt loop if request was cancelled by a Tflush request */
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if (v9fs_request_cancelled(pdu)) {
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err = -EINTR;
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break;
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}
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/* get directory entry from fs driver */
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err = do_readdir(pdu, fidp, &dent);
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if (err || !dent) {
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break;
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}
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/*
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* stop this loop as soon as it would exceed the allowed maximum
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* response message size for the directory entries collected so far,
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* because anything beyond that size would need to be discarded by
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* 9p controller (main thread / top half) anyway
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*/
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v9fs_string_init(&name);
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v9fs_string_sprintf(&name, "%s", dent->d_name);
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len = v9fs_readdir_response_size(&name);
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v9fs_string_free(&name);
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if (size + len > maxsize) {
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/* this is not an error case actually */
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break;
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}
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/* append next node to result chain */
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if (!e) {
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*entries = e = g_malloc0(sizeof(V9fsDirEnt));
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} else {
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e = e->next = g_malloc0(sizeof(V9fsDirEnt));
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}
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e->dent = g_malloc0(sizeof(struct dirent));
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memcpy(e->dent, dent, sizeof(struct dirent));
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/* perform a full stat() for directory entry if requested by caller */
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if (dostat) {
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err = s->ops->name_to_path(
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&s->ctx, &fidp->path, dent->d_name, &path
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);
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if (err < 0) {
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err = -errno;
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break;
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}
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err = s->ops->lstat(&s->ctx, &path, &stbuf);
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if (err < 0) {
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err = -errno;
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break;
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}
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e->st = g_malloc0(sizeof(struct stat));
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memcpy(e->st, &stbuf, sizeof(struct stat));
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}
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size += len;
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saved_dir_pos = dent->d_off;
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}
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/* restore (last) saved position */
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s->ops->seekdir(&s->ctx, &fidp->fs, saved_dir_pos);
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out:
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v9fs_readdir_unlock(&fidp->fs.dir);
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v9fs_path_free(&path);
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if (err < 0) {
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return err;
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}
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return size;
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}
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/**
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* @brief Reads multiple directory entries in one rush.
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*
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* Retrieves the requested (max. amount of) directory entries from the fs
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* driver. This function must only be called by the main IO thread (top half).
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* Internally this function call will be dispatched to a background IO thread
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* (bottom half) where it is eventually executed by the fs driver.
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*
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* @discussion Acquiring multiple directory entries in one rush from the fs
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* driver, instead of retrieving each directory entry individually, is very
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* beneficial from performance point of view. Because for every fs driver
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* request latency is added, which in practice could lead to overall
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* latencies of several hundred ms for reading all entries (of just a single
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* directory) if every directory entry was individually requested from fs
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* driver.
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*
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* @note You must @b ALWAYS call @c v9fs_free_dirents(entries) after calling
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* v9fs_co_readdir_many(), both on success and on error cases of this
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* function, to avoid memory leaks once @p entries are no longer needed.
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*
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* @param pdu - the causing 9p (T_readdir) client request
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* @param fidp - already opened directory where readdir shall be performed on
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* @param entries - output for directory entries (must not be NULL)
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* @param offset - initial position inside the directory the function shall
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* seek to before retrieving the directory entries
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* @param maxsize - maximum result message body size (in bytes)
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* @param dostat - whether a stat() should be performed and returned for
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* each directory entry
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* @returns resulting response message body size (in bytes) on success,
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* negative error code otherwise
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*/
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int coroutine_fn v9fs_co_readdir_many(V9fsPDU *pdu, V9fsFidState *fidp,
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struct V9fsDirEnt **entries,
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off_t offset, int32_t maxsize,
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bool dostat)
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{
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int err = 0;
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if (v9fs_request_cancelled(pdu)) {
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return -EINTR;
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}
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v9fs_co_run_in_worker({
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err = do_readdir_many(pdu, fidp, entries, offset, maxsize, dostat);
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});
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return err;
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}
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off_t v9fs_co_telldir(V9fsPDU *pdu, V9fsFidState *fidp)
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{
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off_t err;
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V9fsState *s = pdu->s;
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if (v9fs_request_cancelled(pdu)) {
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return -EINTR;
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}
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v9fs_co_run_in_worker(
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{
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err = s->ops->telldir(&s->ctx, &fidp->fs);
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if (err < 0) {
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err = -errno;
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}
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});
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return err;
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}
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void coroutine_fn v9fs_co_seekdir(V9fsPDU *pdu, V9fsFidState *fidp,
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off_t offset)
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{
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V9fsState *s = pdu->s;
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if (v9fs_request_cancelled(pdu)) {
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return;
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}
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v9fs_co_run_in_worker(
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{
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s->ops->seekdir(&s->ctx, &fidp->fs, offset);
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});
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}
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void coroutine_fn v9fs_co_rewinddir(V9fsPDU *pdu, V9fsFidState *fidp)
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{
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V9fsState *s = pdu->s;
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if (v9fs_request_cancelled(pdu)) {
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return;
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}
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v9fs_co_run_in_worker(
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{
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s->ops->rewinddir(&s->ctx, &fidp->fs);
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});
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}
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int coroutine_fn v9fs_co_mkdir(V9fsPDU *pdu, V9fsFidState *fidp,
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V9fsString *name, mode_t mode, uid_t uid,
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gid_t gid, struct stat *stbuf)
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{
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int err;
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FsCred cred;
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V9fsPath path;
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V9fsState *s = pdu->s;
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if (v9fs_request_cancelled(pdu)) {
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return -EINTR;
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}
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cred_init(&cred);
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cred.fc_mode = mode;
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cred.fc_uid = uid;
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cred.fc_gid = gid;
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v9fs_path_read_lock(s);
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v9fs_co_run_in_worker(
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{
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err = s->ops->mkdir(&s->ctx, &fidp->path, name->data, &cred);
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if (err < 0) {
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err = -errno;
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} else {
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v9fs_path_init(&path);
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err = v9fs_name_to_path(s, &fidp->path, name->data, &path);
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if (!err) {
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err = s->ops->lstat(&s->ctx, &path, stbuf);
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if (err < 0) {
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err = -errno;
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}
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}
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v9fs_path_free(&path);
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}
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});
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v9fs_path_unlock(s);
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return err;
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}
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int coroutine_fn v9fs_co_opendir(V9fsPDU *pdu, V9fsFidState *fidp)
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{
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int err;
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V9fsState *s = pdu->s;
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if (v9fs_request_cancelled(pdu)) {
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return -EINTR;
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}
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v9fs_path_read_lock(s);
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v9fs_co_run_in_worker(
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{
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err = s->ops->opendir(&s->ctx, &fidp->path, &fidp->fs);
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if (err < 0) {
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err = -errno;
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} else {
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err = 0;
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}
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});
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v9fs_path_unlock(s);
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if (!err) {
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total_open_fd++;
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if (total_open_fd > open_fd_hw) {
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v9fs_reclaim_fd(pdu);
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}
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}
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return err;
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}
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int coroutine_fn v9fs_co_closedir(V9fsPDU *pdu, V9fsFidOpenState *fs)
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{
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int err;
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V9fsState *s = pdu->s;
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if (v9fs_request_cancelled(pdu)) {
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return -EINTR;
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}
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v9fs_co_run_in_worker(
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{
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err = s->ops->closedir(&s->ctx, fs);
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if (err < 0) {
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err = -errno;
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}
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});
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if (!err) {
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total_open_fd--;
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}
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return err;
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}
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