Messages in this thread Patch in this message | | | Date | Thu, 21 Aug 2008 13:06:14 +0200 | From | Louis Rilling <> | Subject | Re: [RFC v2][PATCH 8/9] File descriprtors - dump state |
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On Wed, Aug 20, 2008 at 11:07:16PM -0400, Oren Laadan wrote: > > 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 a > tag and registered in the object hash. > > For each open FD there is a 'struct cr_hdr_fd_ent' with the FD, its tag > 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.
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> diff --git a/checkpoint/ckpt_file.c b/checkpoint/ckpt_file.c > new file mode 100644 > index 0000000..18faaf1 > --- /dev/null > +++ b/checkpoint/ckpt_file.c > @@ -0,0 +1,234 @@ > +/* > + * 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 <linux/kernel.h> > +#include <linux/sched.h> > +#include <linux/file.h> > +#include <linux/fdtable.h> > + > +#include "ckpt.h" > +#include "ckpt_hdr.h" > +#include "ckpt_file.h" > + > +#define CR_DEFAULT_FDTABLE 128 > + > +/** > + * cr_scan_fds - scan file table and construct array of open fds > + * @files: files_struct pointer > + * @fdtable: (output) array of open fds > + * @return: the number of open fds found > + * > + * Allocates the file descriptors array (*fdtable), caller should free > + */ > +int cr_scan_fds(struct files_struct *files, int **fdtable) > +{ > + int i, j, n, max; > + struct fdtable *fdt; > + int *fdlist; > + > + max = CR_DEFAULT_FDTABLE; > + > + repeat: > + fdlist = kmalloc(max * sizeof(*fdlist), GFP_KERNEL); > + if (!fdlist) > + return -ENOMEM; > + > + j = 0; > + n = 0; > + > + spin_lock(&files->file_lock); > + fdt = files_fdtable(files); > + for (;;) { > + unsigned long set; > + i = j * __NFDBITS; > + if (i >= fdt->max_fds) > + break; > + set = fdt->open_fds->fds_bits[j++];
Why not simply use fcheck_files(files, n) and check if the result is not NULL?
> + while (set) { > + if (set & 1) { > + if (unlikely(n == max)) { > + spin_unlock(&files->file_lock); > + kfree(fdlist); > + max *= 2; > + if (max < 0) /* overflow ? */ > + return -EMFILE; > + goto repeat; > + } > + fdlist[n++] = i; > + } > + i++; > + set >>= 1; > + } > + } > + spin_unlock(&files->file_lock); > + > + *fdtable = fdlist; > + 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 ptag) > +{ > + struct cr_hdr h; > + struct cr_hdr_fd_data *hh = ctx->hbuf; > + struct dentry *dent = file->f_dentry; > + struct inode *inode = dent->d_inode; > + char *fname; > + int flen, how, ret; > + > + h.type = CR_HDR_FD_DATA; > + h.len = sizeof(*hh); > + h.ptag = ptag; > + > + BUG_ON(!inode); > + > + flen = PAGE_SIZE; > + fname = cr_fill_fname(&file->f_path, ctx->vfsroot, ctx->tbuf, &flen); > + if (IS_ERR(fname)) > + return PTR_ERR(fname); > + > + hh->f_flags = file->f_flags; > + hh->f_mode = file->f_mode; > + hh->f_pos = file->f_pos; > + hh->f_uid = file->f_uid; > + hh->f_gid = file->f_gid; > + hh->f_version = file->f_version; > + /* FIX: need also file->f_owner */ > + > + switch(inode->i_mode & S_IFMT) { > + case S_IFREG: > + how = CR_FD_FILE; > + break; > + case S_IFDIR: > + how = CR_FD_DIR; > + break; > + case S_IFLNK: > + how = CR_FD_LINK; > + break; > + default: > + return -EBADF; > + } > + > + /* FIX: check if the file/dir/link is unlinked */ > + > + BUG_ON(!flen); > + > + ret = cr_write_obj(ctx, &h, hh); > + if (!ret && flen) > + ret = cr_write_str(ctx, fname, flen); > + > + return ret; > +} > + > +/** > + * cr_write_fd_ent - dump the state of a given file descriptor > + * @ctx: checkpoint context > + * @files: files_struct pointer > + * @fd: file descriptor > + * + * Save the state of the file descriptor; look up the actual file > pointer > + * in the hash table, and if found save the matching tag, otherwise call > + * 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 = ctx->hbuf; > + struct file *file = NULL; > + struct fdtable *fdt; > + int coe, tag, ret; > + > + /* make sure hh->fd (that is of type __u16) doesn't overflow */ > + if (fd > USHORT_MAX) { > + pr_warning("CR: open files table too big (%d)\n", USHORT_MAX); > + return -EMFILE; > + } > + > + rcu_read_lock(); > + fdt = files_fdtable(files); > + if (fd < fdt->max_fds) > + file = rcu_dereference(fdt->fd[fd]);
You should probably use fcheck_files() instead of copying its code here. I agree that this means dereferencing files->fdt a second time below, but is it so performance critical?
> + if (file) { > + coe = FD_ISSET(fd, fdt->close_on_exec); > + get_file(file); > + } > + rcu_read_unlock(); > + > + /* sanity check (although this shouldn't happen) */ > + if (unlikely(!file)) > + return -EBADF; > + > + ret = cr_obj_add_ptr(ctx, (void *) file, &tag, CR_OBJ_FILE, 0); > + cr_debug("fd %d tag %d file %p c-o-e %d)\n", fd, tag, file, coe); > + > + if (ret >= 0) { > + int new = ret; > + > + h.type = CR_HDR_FD_ENT; > + h.len = sizeof(*hh); > + h.ptag = 0; > + + hh->tag = tag; ^ |
> + hh->fd = fd; > + hh->close_on_exec = coe; > + > + ret = cr_write_obj(ctx, &h, hh); > + > + /* new==1 if-and-only-if file was new and added to hash */ > + if (!ret && new) > + ret = cr_write_fd_data(ctx, file, tag); > + } > + > + 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 = ctx->hbuf; > + struct files_struct *files; > + int *fdtable; > + int nfds, n, ret; > + > + h.type = CR_HDR_FILES; > + h.len = sizeof(*hh); > + h.ptag = task_pid_vnr(t); > + > + files = get_files_struct(t); > + > + nfds = cr_scan_fds(files, &fdtable); > + if (nfds < 0) { > + ret = nfds; > + goto out; > + } > + + hh->tag = 0; ^ |
> + hh->nfds = nfds; > + > + ret = cr_write_obj(ctx, &h, 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, n); > + if (ret < 0) > + break; > + } > + > + clean: > + kfree(fdtable); > + out: > + put_files_struct(files); > + > + return ret; > +}
[...]
> diff --git a/checkpoint/ckpt_hdr.h b/checkpoint/ckpt_hdr.h > index a3919cf..a8a37db 100644 > --- a/checkpoint/ckpt_hdr.h > +++ b/checkpoint/ckpt_hdr.h
[...]
> @@ -114,4 +125,24 @@ struct cr_hdr_vma { > > } __attribute__ ((aligned (8))); > > +struct cr_hdr_files { > + __u32 tag; /* sharing identifier */ > + __u32 nfds; > +} __attribute__ ((aligned (8))); > + > +struct cr_hdr_fd_ent { > + __u32 tag; > + __u16 fd; > + __u16 close_on_exec; > +} __attribute__ ((aligned (8))); > + > +struct cr_hdr_fd_data { > + __u16 how; > + __u16 f_mode; > + __u32 f_flags; > + __u32 f_uid, f_gid;
We are not at a 64bits boundary here. Should add one __32 padding or reorder the fields.
> + __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/
-- Dr Louis Rilling Kerlabs Skype: louis.rilling Batiment Germanium Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes http://www.kerlabs.com/ 35700 Rennes[unhandled content-type:application/pgp-signature] | |