Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752357AbYJTFoZ (ORCPT ); Mon, 20 Oct 2008 01:44:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753388AbYJTFnZ (ORCPT ); Mon, 20 Oct 2008 01:43:25 -0400 Received: from serrano.cc.columbia.edu ([128.59.29.6]:58670 "EHLO serrano.cc.columbia.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751126AbYJTFnV (ORCPT ); Mon, 20 Oct 2008 01:43:21 -0400 From: Oren Laadan To: Linus Torvalds Cc: containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, Thomas Gleixner , Serge Hallyn , Dave Hansen , Ingo Molnar , "H. Peter Anvin" , Alexander Viro , Oren Laadan Subject: [RFC v7][PATCH 8/9] Dump open file descriptors Date: Mon, 20 Oct 2008 01:40:36 -0400 Message-Id: <1224481237-4892-9-git-send-email-orenl@cs.columbia.edu> X-Mailer: git-send-email 1.6.0.1 In-Reply-To: <1224481237-4892-1-git-send-email-orenl@cs.columbia.edu> References: <1224481237-4892-1-git-send-email-orenl@cs.columbia.edu> X-No-Spam-Score: Local Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10900 Lines: 402 Dump the files_struct of a task with 'struct cr_hdr_files', followed by all open file descriptors. Since FDs can be shared, they are assigned an objref and registered in the object hash. For each open FD there is a 'struct cr_hdr_fd_ent' with the FD, its objref and its close-on-exec property. If the FD is to be saved (first time) then this is followed by a 'struct cr_hdr_fd_data' with the FD state. Then will come the next FD and so on. This patch only handles basic FDs - regular files, directories and also symbolic links. Signed-off-by: Oren Laadan Acked-by: Serge Hallyn Signed-off-by: Dave Hansen --- checkpoint/Makefile | 2 +- checkpoint/checkpoint.c | 4 + checkpoint/checkpoint_file.h | 17 +++ checkpoint/ckpt_file.c | 231 ++++++++++++++++++++++++++++++++++++++++ include/linux/checkpoint.h | 7 +- include/linux/checkpoint_hdr.h | 32 ++++++- 6 files changed, 288 insertions(+), 5 deletions(-) create mode 100644 checkpoint/checkpoint_file.h create mode 100644 checkpoint/ckpt_file.c diff --git a/checkpoint/Makefile b/checkpoint/Makefile index 9843fb9..7496695 100644 --- a/checkpoint/Makefile +++ b/checkpoint/Makefile @@ -3,4 +3,4 @@ # obj-$(CONFIG_CHECKPOINT_RESTART) += sys.o checkpoint.o restart.o objhash.o \ - ckpt_mem.o rstr_mem.o + ckpt_mem.o rstr_mem.o ckpt_file.o diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c index d4c1b31..87420dc 100644 --- a/checkpoint/checkpoint.c +++ b/checkpoint/checkpoint.c @@ -203,6 +203,10 @@ static int cr_write_task(struct cr_ctx *ctx, struct task_struct *t) cr_debug("memory: ret %d\n", ret); if (ret < 0) goto out; + ret = cr_write_files(ctx, t); + cr_debug("files: ret %d\n", ret); + if (ret < 0) + goto out; ret = cr_write_thread(ctx, t); cr_debug("thread: ret %d\n", ret); if (ret < 0) diff --git a/checkpoint/checkpoint_file.h b/checkpoint/checkpoint_file.h new file mode 100644 index 0000000..9dc3eba --- /dev/null +++ b/checkpoint/checkpoint_file.h @@ -0,0 +1,17 @@ +#ifndef _CHECKPOINT_CKPT_FILE_H_ +#define _CHECKPOINT_CKPT_FILE_H_ +/* + * Checkpoint file descriptors + * + * Copyright (C) 2008 Oren Laadan + * + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file COPYING in the main directory of the Linux + * distribution for more details. + */ + +#include + +int cr_scan_fds(struct files_struct *files, int **fdtable); + +#endif /* _CHECKPOINT_CKPT_FILE_H_ */ diff --git a/checkpoint/ckpt_file.c b/checkpoint/ckpt_file.c new file mode 100644 index 0000000..767fc01 --- /dev/null +++ b/checkpoint/ckpt_file.c @@ -0,0 +1,231 @@ +/* + * Checkpoint file descriptors + * + * Copyright (C) 2008 Oren Laadan + * + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file COPYING in the main directory of the Linux + * distribution for more details. + */ + +#include +#include +#include +#include +#include +#include + +#include "checkpoint_file.h" + +#define CR_DEFAULT_FDTABLE 256 /* an initial guess */ + +/** + * cr_scan_fds - scan file table and construct array of open fds + * @files: files_struct pointer + * @fdtable: (output) array of open fds + * + * Returns the number of open fds found, and also the file table + * array via *fdtable. The caller should free the array. + * + * The caller must validate the file descriptors collected in the + * array before using them, e.g. by using fcheck_files(), in case + * the task's fdtable changes in the meantime. + */ +int cr_scan_fds(struct files_struct *files, int **fdtable) +{ + struct fdtable *fdt; + int *fds; + int i, n = 0; + int tot = CR_DEFAULT_FDTABLE; + + fds = kmalloc(tot * sizeof(*fds), GFP_KERNEL); + if (!fds) + return -ENOMEM; + + /* + * We assume that the target task is frozen (or that we checkpoint + * ourselves), so we can safely proceed after krealloc() from where + * we left off; in the worst cases restart will fail. + */ + + spin_lock(&files->file_lock); + rcu_read_lock(); + fdt = files_fdtable(files); + for (i = 0; i < fdt->max_fds; i++) { + if (!fcheck_files(files, i)) + continue; + if (n == tot) { + /* + * fcheck_files() is safe with drop/re-acquire + * of the lock, because it tests: fd < max_fds + */ + spin_unlock(&files->file_lock); + rcu_read_unlock(); + tot *= 2; /* won't overflow: kmalloc will fail */ + fds = krealloc(fds, tot * sizeof(*fds), GFP_KERNEL); + if (!fds) { + kfree(fds); + return -ENOMEM; + } + rcu_read_lock(); + spin_lock(&files->file_lock); + } + fds[n++] = i; + } + rcu_read_unlock(); + spin_unlock(&files->file_lock); + + *fdtable = fds; + return n; +} + +/* cr_write_fd_data - dump the state of a given file pointer */ +static int cr_write_fd_data(struct cr_ctx *ctx, struct file *file, int parent) +{ + struct cr_hdr h; + struct cr_hdr_fd_data *hh = cr_hbuf_get(ctx, sizeof(*hh)); + struct dentry *dent = file->f_dentry; + struct inode *inode = dent->d_inode; + enum fd_type fd_type; + int ret; + + h.type = CR_HDR_FD_DATA; + h.len = sizeof(*hh); + h.parent = parent; + + hh->f_flags = file->f_flags; + hh->f_mode = file->f_mode; + hh->f_pos = file->f_pos; + hh->f_version = file->f_version; + /* FIX: need also file->uid, file->gid, file->f_owner, etc */ + + switch (inode->i_mode & S_IFMT) { + case S_IFREG: + fd_type = CR_FD_FILE; + break; + case S_IFDIR: + fd_type = CR_FD_DIR; + break; + case S_IFLNK: + fd_type = CR_FD_LINK; + break; + default: + cr_hbuf_put(ctx, sizeof(*hh)); + return -EBADF; + } + + /* FIX: check if the file/dir/link is unlinked */ + hh->fd_type = fd_type; + + ret = cr_write_obj(ctx, &h, hh); + cr_hbuf_put(ctx, sizeof(*hh)); + if (ret < 0) + return ret; + + return cr_write_fname(ctx, &file->f_path, ctx->vfsroot); +} + +/** + * cr_write_fd_ent - dump the state of a given file descriptor + * @ctx: checkpoint context + * @files: files_struct pointer + * @fd: file descriptor + * + * Saves the state of the file descriptor; looks up the actual file + * pointer in the hash table, and if found saves the matching objref, + * otherwise calls cr_write_fd_data to dump the file pointer too. + */ +static int +cr_write_fd_ent(struct cr_ctx *ctx, struct files_struct *files, int fd) +{ + struct cr_hdr h; + struct cr_hdr_fd_ent *hh = cr_hbuf_get(ctx, sizeof(*hh)); + struct file *file = NULL; + struct fdtable *fdt; + int coe, objref, new, ret; + + rcu_read_lock(); + fdt = files_fdtable(files); + file = fcheck_files(files, fd); + if (file) { + coe = FD_ISSET(fd, fdt->close_on_exec); + get_file(file); + } + rcu_read_unlock(); + + /* sanity check (although this shouldn't happen) */ + if (!file) { + ret = -EBADF; + goto out; + } + + new = cr_obj_add_ptr(ctx, file, &objref, CR_OBJ_FILE, 0); + cr_debug("fd %d objref %d file %p c-o-e %d)\n", fd, objref, file, coe); + + if (new < 0) { + ret = new; + goto out; + } + + h.type = CR_HDR_FD_ENT; + h.len = sizeof(*hh); + h.parent = 0; + + hh->objref = objref; + hh->fd = fd; + hh->close_on_exec = coe; + + ret = cr_write_obj(ctx, &h, hh); + if (ret < 0) + goto out; + + /* new==1 if-and-only-if file was newly added to hash */ + if (new) + ret = cr_write_fd_data(ctx, file, objref); + +out: + cr_hbuf_put(ctx, sizeof(*hh)); + fput(file); + return ret; +} + +int cr_write_files(struct cr_ctx *ctx, struct task_struct *t) +{ + struct cr_hdr h; + struct cr_hdr_files *hh = cr_hbuf_get(ctx, sizeof(*hh)); + struct files_struct *files; + int *fdtable; + int nfds, n, ret; + + h.type = CR_HDR_FILES; + h.len = sizeof(*hh); + h.parent = task_pid_vnr(t); + + files = get_files_struct(t); + + nfds = cr_scan_fds(files, &fdtable); + if (nfds < 0) { + put_files_struct(files); + return nfds; + } + + hh->objref = 0; /* will be meaningful with multiple processes */ + hh->nfds = nfds; + + ret = cr_write_obj(ctx, &h, hh); + cr_hbuf_put(ctx, sizeof(*hh)); + if (ret < 0) + goto clean; + + cr_debug("nfds %d\n", nfds); + for (n = 0; n < nfds; n++) { + ret = cr_write_fd_ent(ctx, files, fdtable[n]); + if (ret < 0) + break; + } + + clean: + kfree(fdtable); + put_files_struct(files); + return ret; +} diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h index 2da3a9f..d6bf6dc 100644 --- a/include/linux/checkpoint.h +++ b/include/linux/checkpoint.h @@ -13,7 +13,7 @@ #include #include -#define CR_VERSION 1 +#define CR_VERSION 2 struct cr_ctx { pid_t pid; /* container identifier */ @@ -79,11 +79,12 @@ extern int cr_read_fname(struct cr_ctx *ctx, void *fname, int n); extern struct file *cr_read_open_fname(struct cr_ctx *ctx, int flags, int mode); +extern int do_checkpoint(struct cr_ctx *ctx); extern int cr_write_mm(struct cr_ctx *ctx, struct task_struct *t); -extern int cr_read_mm(struct cr_ctx *ctx); +extern int cr_write_files(struct cr_ctx *ctx, struct task_struct *t); -extern int do_checkpoint(struct cr_ctx *ctx); extern int do_restart(struct cr_ctx *ctx); +extern int cr_read_mm(struct cr_ctx *ctx); /* there are from fs/read_write.c, not exported otherwise in a header */ extern loff_t file_pos_read(struct file *file); diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h index 2b110f1..cbb920f 100644 --- a/include/linux/checkpoint_hdr.h +++ b/include/linux/checkpoint_hdr.h @@ -17,7 +17,7 @@ /* * To maintain compatibility between 32-bit and 64-bit architecture flavors, * keep data 64-bit aligned: use padding for structure members, and use - * __attribute__ ((aligned (8))) for the entire structure. + * __attribute__((aligned(8))) for the entire structure. */ /* records: generic header */ @@ -43,6 +43,10 @@ enum { CR_HDR_PGARR, CR_HDR_MM_CONTEXT, + CR_HDR_FILES = 301, + CR_HDR_FD_ENT, + CR_HDR_FD_DATA, + CR_HDR_TAIL = 5001 }; @@ -105,4 +109,30 @@ struct cr_hdr_pgarr { __u64 nr_pages; /* number of pages to saved */ } __attribute__((aligned(8))); +struct cr_hdr_files { + __u32 objref; /* identifier for shared objects */ + __u32 nfds; +} __attribute__((aligned(8))); + +struct cr_hdr_fd_ent { + __u32 objref; /* identifier for shared objects */ + __s32 fd; + __u32 close_on_exec; +} __attribute__((aligned(8))); + +/* fd types */ +enum fd_type { + CR_FD_FILE = 1, + CR_FD_DIR, + CR_FD_LINK +}; + +struct cr_hdr_fd_data { + __u16 fd_type; + __u16 f_mode; + __u32 f_flags; + __u64 f_pos; + __u64 f_version; +} __attribute__((aligned(8))); + #endif /* _CHECKPOINT_CKPT_HDR_H_ */ -- 1.5.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/