Save/restore epoll items during checkpoint/restart respectively.
Tests for the cr_tests suite to follow. Tests pass on i386.
TODOs (search the patch for "TODO") that could probably use some
comments:
What to do when there's a "possible checkpoint obj leak"? (search patch
for this string to see what I'm talking about)
Ensure get_current_user will be correct (a userns question/issue?).
kmalloc failures should be dealt with more kindly than just error-out
because epoll is made to poll many thousands of file
descriptors.
This seems like a more general problem with some of the
ckpt_hdr* functions than an epoll problem but...
Pick better errnos for some cases.
Signed-off-by: Matt Helsley <matthltc@xxxxxxxxxx>
Cc: Oren Laadan <orenl@xxxxxxxxxxx>
---
checkpoint/files.c | 35 +++++
checkpoint/restart.c | 2 +-
fs/eventpoll.c | 280 +++++++++++++++++++++++++++++++++++++-
include/linux/checkpoint.h | 1 +
include/linux/checkpoint_hdr.h | 14 ++
include/linux/checkpoint_types.h | 2 +
include/linux/eventpoll.h | 14 ++-
7 files changed, 345 insertions(+), 3 deletions(-)
diff --git a/checkpoint/files.c b/checkpoint/files.c
index 204055b..8f86dcc 100644
--- a/checkpoint/files.c
+++ b/checkpoint/files.c
@@ -21,6 +21,8 @@
#include <linux/syscalls.h>
#include <linux/checkpoint.h>
#include <linux/checkpoint_hdr.h>
+#include <linux/deferqueue.h>
+#include <linux/eventpoll.h>
#include <net/sock.h>
@@ -289,11 +291,24 @@ static int do_checkpoint_file_table(struct ckpt_ctx *ctx,
goto out;
ckpt_debug("nfds %d\n", nfds);
+ ctx->files_deferq = deferqueue_create();
+ if (!ctx->files_deferq) {
+ ret = -ENOMEM;
+ goto out;
+ }
for (n = 0; n < nfds; n++) {
ret = checkpoint_file_desc(ctx, files, fdtable[n]);
if (ret < 0)
break;
}
+ if (!ret) {
+ ret = deferqueue_run(ctx->files_deferq);
+ if (ret > 0) {
+ pr_warning("c/r: files deferqueue had %d entries\n", ret);
+ ret = 0;
+ }
+ }
+ deferqueue_destroy(ctx->files_deferq);
out:
kfree(fdtable);
return ret;
@@ -572,6 +587,14 @@ static struct restore_file_ops restore_file_ops[] = {
.file_type = CKPT_FILE_SOCKET,
.restore = sock_file_restore,
},
+#ifdef CONFIG_EPOLL
+ /* epoll */
+ {
+ .file_name = "EPOLL",
+ .file_type = CKPT_FILE_EPOLL,
+ .restore = ep_file_restore,
+ },
+#endif
};
static struct file *do_restore_file(struct ckpt_ctx *ctx)
@@ -692,11 +715,23 @@ static struct files_struct *do_restore_file_table(struct ckpt_ctx *ctx)
if (ret < 0)
goto out;
+ ret = -ENOMEM;
+ ctx->files_deferq = deferqueue_create();
+ if (!ctx->files_deferq)
+ goto out;
for (i = 0; i < h->fdt_nfds; i++) {
ret = restore_file_desc(ctx);
if (ret < 0)
break;
}
+ if (!ret) {
+ ret = deferqueue_run(ctx->files_deferq);
+ if (ret > 0) {
+ pr_warning("c/r: files deferqueue had %d entries\n", ret);
+ ret = 0;
+ }
+ }
+ deferqueue_destroy(ctx->files_deferq);
out:
ckpt_hdr_put(ctx, h);
if (!ret) {
diff --git a/checkpoint/restart.c b/checkpoint/restart.c
index 4fdae78..3a7d914 100644
--- a/checkpoint/restart.c
+++ b/checkpoint/restart.c
@@ -164,7 +164,7 @@ int _ckpt_read_string(struct ckpt_ctx *ctx, void *ptr, int len)
*
* Return: new buffer allocated on success, error pointer otherwise
*/
-static void *ckpt_read_obj(struct ckpt_ctx *ctx, int len, int max)
+void *ckpt_read_obj(struct ckpt_ctx *ctx, int len, int max)
{
struct ckpt_hdr hh;
struct ckpt_hdr *h;
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 085c5c0..7f7070f 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -671,10 +671,19 @@ static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait)
return pollflags != -1 ? pollflags : 0;
}
+#ifdef CONFIG_CHECKPOINT
+static int ep_eventpoll_checkpoint(struct ckpt_ctx *ctx, struct file *file);
+static int ep_file_collect(struct ckpt_ctx *ctx, struct file *file);
+#else
+#define ep_eventpoll_checkpoint NULL
+#endif
+
/* File callbacks that implement the eventpoll file behaviour */
static const struct file_operations eventpoll_fops = {
.release = ep_eventpoll_release,
- .poll = ep_eventpoll_poll
+ .poll = ep_eventpoll_poll,
+ .checkpoint = ep_eventpoll_checkpoint,
+ .collect = ep_file_collect,
};
/* Fast test to see if the file is an evenpoll file */
@@ -1413,6 +1422,275 @@ SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
#endif /* HAVE_SET_RESTORE_SIGMASK */
+#ifdef CONFIG_CHECKPOINT
+#include <linux/checkpoint.h>
+#include <linux/checkpoint_hdr.h>
+#include <linux/deferqueue.h>
+
+static int ep_file_collect(struct ckpt_ctx *ctx, struct file *file)
+{
+ struct rb_node *rbp;
+ struct eventpoll *ep;
+ int ret = 0;
+
+ if (!is_file_epoll(file))
+ return 0;
+
+ ep = file->private_data;
+ mutex_lock(&ep->mtx);
+ for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
+ struct epitem *epi;
+
+ epi = rb_entry(rbp, struct epitem, rbn);
+ ret = ckpt_obj_collect(ctx, epi->ffd.file, CKPT_OBJ_FILE);
+ if (ret < 0)
+ break;
+ }
+ mutex_unlock(&ep->mtx);
+ return ret;
+}
+
+struct epoll_deferq_entry {
+ struct ckpt_ctx *ctx;
+ struct file *epfile;
+};
+
+static int ep_items_checkpoint(void *data)
+{
+ struct epoll_deferq_entry *ep_dq_entry = data;
+ struct ckpt_ctx *ctx;
+ struct file *file;
+ struct ckpt_eventpoll_items *h;
+ struct rb_node *rbp;
+ struct eventpoll *ep;
+ int i, ret = -ENOMEM;
+
+ file = ep_dq_entry->epfile;
+ ctx = ep_dq_entry->ctx;
+
+ ep = file->private_data;
+ mutex_lock(&ep->mtx);
+ for (i = 0, rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp), i++) {}
+ mutex_unlock(&ep->mtx);
+
+ /* TODO likely allocation failure when lots of epoll items */
+ h = ckpt_hdr_get_type(ctx, sizeof(*h) + i*sizeof(h->items[0]),
+ CKPT_HDR_FILE_EPOLL_ITEMS);
+ if (!h)
+ goto out;
+
+ ret = -ENODEV;
+ h->num_items = i;
+ h->epfile_objref = ckpt_obj_lookup(ctx, file, CKPT_OBJ_FILE);
+ if (h->epfile_objref <= 0)
+ goto out;
+
+ ret = 0;
+ mutex_lock(&ep->mtx);
+ for (i = 0, rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp), i++) {
+ struct epitem *epi;
+ int objref;
+
+ epi = rb_entry(rbp, struct epitem, rbn);
+ objref = ckpt_obj_lookup(ctx, epi->ffd.file, CKPT_OBJ_FILE);
+ if (objref <= 0) {
+ /* TODO error -- possible checkpoint obj leak */
+ ret = -ENODEV;
+ break;
+ }
+ h->items[i].fd = epi->ffd.fd;
+ h->items[i].file_objref = objref;
+ h->items[i].events = epi->event.events;
+ h->items[i].data = epi->event.data;
+ }
+ mutex_unlock(&ep->mtx);
+ if (h && !ret)
+ ret = ckpt_write_obj(ctx, &h->h);
+ if (!ret && (i != h->num_items)) {
+ /* TODO error -- possible checkpoint obj leak */
+ }
+out:
+ if (h)
+ ckpt_hdr_put(ctx, &h->h);
+ return ret;
+}
+
+static int ep_eventpoll_checkpoint(struct ckpt_ctx *ctx, struct file *file)
+{
+ struct ckpt_hdr_file *h;
+ struct epoll_deferq_entry ep_dq_entry;
+ int ret = -ENOMEM;
+
+ h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_FILE);
+ if (!h)
+ goto out_print;
+ h->f_type = CKPT_FILE_EPOLL;
+ ret = checkpoint_file_common(ctx, file, h);
+ if (ret < 0)
+ goto out;
+ ret = ckpt_write_obj(ctx, &h->h);
+ if (ret < 0)
+ goto out;
+
+ /*
+ * Defer saving the epoll items until all of the ffd.file pointers
+ * have an objref; after the file table has been checkpointed.
+ */
+ ep_dq_entry.ctx = ctx;
+ ep_dq_entry.epfile = file;
+ ret = deferqueue_add(ctx->files_deferq, &ep_dq_entry,
+ sizeof(ep_dq_entry), ep_items_checkpoint, NULL);
+out:
+ ckpt_hdr_put(ctx, h);
+out_print:
+ return ret;
+}
+
+static int ep_items_restore(void *data)
+{
+ struct ckpt_ctx *ctx = *((struct ckpt_ctx**)data);
+ struct ckpt_eventpoll_items *h;
+ struct eventpoll *ep;
+ struct file *epfile = NULL;
+ int ret, i = 0, remaining_watches;
+
+ /*
+ * TODO possible kmalloc failure due to too many watches.
+ */
+ h = ckpt_read_obj(ctx, 0,
+ sizeof(*h) + max_user_watches*sizeof(h->items[0]));
+ if (IS_ERR(h))
+ return PTR_ERR(h);
+
+ ret = -EINVAL;
+ if ((h->h.type != CKPT_HDR_FILE_EPOLL_ITEMS) ||
+ (h->h.len < sizeof(*h)))
+ goto out;
+
+ /* Make sure the items match the size we expect */
+ if (h->num_items != ((h->h.len - sizeof(*h)) / sizeof(h->items[0])))
+ goto out;
+
+ epfile = ckpt_obj_fetch(ctx, h->epfile_objref, CKPT_OBJ_FILE);
+ if (IS_ERR(epfile)) {
+ ret = PTR_ERR(epfile);
+ goto out;
+ }
+ ret = -ENOMSG;
+ if (!is_file_epoll(epfile))
+ goto out;
+
+ ep = epfile->private_data;
+
+ ret = -ENOSPC;
+ remaining_watches = (max_user_watches -
+ atomic_read(&ep->user->epoll_watches));
+ if (h->num_items > remaining_watches)
+ goto out;
+
+ ret = 0;
+ /* Restore the epoll items/watches */
+ for (i = 0; !ret && i < h->num_items; i++) {
+ /*
+ * Loop body like multiple epoll_ctl(ep, ADD, event)
+ * calls except we've already done much of the checking.
+ */
+ struct epoll_event epev;
+ struct epitem *epi;
+ struct file *tfile;
+
+ epev.events = h->items[i].events;
+ epev.data = h->items[i].data;
+
+ /* Get the file* for the target file */
+ if (h->items[i].file_objref <= 0) {
+ ret = -EINVAL;
+ break;
+ }
+
+ tfile = ckpt_obj_fetch(ctx, h->items[i].file_objref,
+ CKPT_OBJ_FILE);
+ if (IS_ERR(tfile)) {
+ ret = PTR_ERR(tfile);
+ break;
+ }
+
+ /* The target file must support poll */
+ if (!tfile->f_op || !tfile->f_op->poll) {
+ ret = -EPERM;
+ break;
+ }
+
+ /* Cannot add an epoll file descriptor inside itself. */
+ if (epfile == tfile) {
+ ret = -EINVAL;
+ break;
+ }
+
+ mutex_lock(&ep->mtx);
+ epi = ep_find(ep, tfile, h->items[i].fd);
+ if (!epi) {
+ epev.events |= POLLERR | POLLHUP;
+ ret = ep_insert(ep, &epev, tfile, h->items[i].fd);
+ } else
+ ret = -EEXIST;
+ mutex_unlock(&ep->mtx);
+ }
+out:
+ ckpt_hdr_put(ctx, h);
+ return ret;
+}
+
+/* TODO confirm that get_current_user() has been restored */
+struct file* ep_file_restore(struct ckpt_ctx *ctx,
+ struct ckpt_hdr_file *h)
+{
+ struct file *epfile;
+ int epfd, ret;
+
+ if (h->h.type != CKPT_HDR_FILE ||
+ h->h.len != sizeof(*h) ||
+ h->f_type != CKPT_FILE_EPOLL)
+ return ERR_PTR(-EINVAL);
+
+ /*
+ * TODO Normally h->f_flags contains flags that epoll_create() won't
+ * accept. Right now we pass only those flags it will accept here
+ * and restore the rest during the "common" file restore. Check
+ * to make sure we're not missing anything.
+ */
+ epfd = sys_epoll_create1(h->f_flags & EPOLL_CLOEXEC);
+ if (epfd < 0)
+ return ERR_PTR(epfd);
+ epfile = fget(epfd);
+ if (!epfile)
+ return ERR_PTR(-ENOENT); /* TODO pick better error? */
+
+ ret = restore_file_common(ctx, epfile, h);
+ if (ret < 0)
+ goto fput_out;
+
+ /*
+ * Now we have the file and file descriptor but the epoll set is empty.
+ * Defer restoring the epoll set until we encounter its corresponding
+ * items. Note that this effectively counts the number of
+ * ckpt_eventpoll_items blocks we should expect -- we rely on the
+ * epfile_objref of those blocks to associate them with the proper
+ * file.
+ */
+ ret = deferqueue_add(ctx->files_deferq, &ctx, sizeof(ctx),
+ ep_items_restore, NULL);
+ if (ret < 0) {
+fput_out:
+ fput(epfile);
+ epfile = ERR_PTR(ret);
+ }
+ sys_close(epfd);
+ return epfile;
+}
+
+#endif /* CONFIG_CHECKPOINT */
+
static int __init eventpoll_init(void)
{
struct sysinfo si;
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 761cad5..053c6c0 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -69,6 +69,7 @@ extern int _ckpt_read_obj_type(struct ckpt_ctx *ctx,
extern int _ckpt_read_nbuffer(struct ckpt_ctx *ctx, void *ptr, int len);
extern int _ckpt_read_buffer(struct ckpt_ctx *ctx, void *ptr, int len);
extern int _ckpt_read_string(struct ckpt_ctx *ctx, void *ptr, int len);
+extern void *ckpt_read_obj(struct ckpt_ctx *ctx, int len, int max);
extern void *ckpt_read_obj_type(struct ckpt_ctx *ctx, int len, int type);
extern void *ckpt_read_buf_type(struct ckpt_ctx *ctx, int len, int type);
extern int ckpt_read_payload(struct ckpt_ctx *ctx,
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index 4d5c22a..3a3e530 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -76,6 +76,7 @@ enum {
CKPT_HDR_FILE_NAME,
CKPT_HDR_FILE,
CKPT_HDR_PIPE_BUF,
+ CKPT_HDR_FILE_EPOLL_ITEMS, /* Follows file-table */
CKPT_HDR_MM = 401,
CKPT_HDR_VMA,
@@ -342,6 +343,7 @@ enum file_type {
CKPT_FILE_PIPE,
CKPT_FILE_FIFO,
CKPT_FILE_SOCKET,
+ CKPT_FILE_EPOLL,
CKPT_FILE_MAX
};
@@ -426,6 +428,18 @@ struct ckpt_hdr_file_socket {
struct ckpt_hdr_socket socket;
} __attribute__((aligned(8)));
+struct ckpt_eventpoll_items {
+ struct ckpt_hdr h;
+ __s32 epfile_objref;
+ __u32 num_items;
+ struct {
+ __u64 data;
+ __u32 fd;
+ __s32 file_objref;
+ __u32 events;
+ } items[0];
+} __attribute__((aligned(8)));
+
struct ckpt_hdr_utsns {
struct ckpt_hdr h;
char sysname[__NEW_UTS_LEN + 1];
diff --git a/include/linux/checkpoint_types.h b/include/linux/checkpoint_types.h
index e98251b..51cdd0c 100644
--- a/include/linux/checkpoint_types.h
+++ b/include/linux/checkpoint_types.h
@@ -48,6 +48,8 @@ struct ckpt_ctx {
struct ckpt_obj_hash *obj_hash; /* repository for shared objects */
struct deferqueue_head *deferqueue; /* queue of deferred work */
+ struct deferqueue_head *files_deferq; /* deferred work to do after
+ saving file table */
struct path fs_mnt; /* container root (FIXME) */
diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
index f6856a5..ff3de38 100644
--- a/include/linux/eventpoll.h
+++ b/include/linux/eventpoll.h
@@ -95,11 +95,23 @@ static inline void eventpoll_release(struct file *file)
eventpoll_release_file(file);
}
+#ifdef CONFIG_CHECKPOINT
+#include <linux/checkpoint_hdr.h>
+extern struct file* ep_file_restore(struct ckpt_ctx *ctx,
+ struct ckpt_hdr_file *h);
+#endif
#else
static inline void eventpoll_init_file(struct file *file) {}
static inline void eventpoll_release(struct file *file) {}
-
+#ifdef CONFIG_CHECKPOINT
+#include <linux/checkpoint_hdr.h>
+static inline struct file* ep_file_restore(struct ckpt_ctx *ctx,
+ struct ckpt_hdr_file *ptr)
+{
+ return NULL;
+}
+#endif
#endif
#endif /* #ifdef __KERNEL__ */
--
1.5.6.3
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