[Devel] Re: [PATCH 06/17][cr][v4]: Checkpoint file-locks
Oren Laadan
orenl at cs.columbia.edu
Thu Sep 16 17:03:06 PDT 2010
On 08/16/2010 03:43 PM, Sukadev Bhattiprolu wrote:
> While checkpointing each file-descriptor, find all the locks on the
> file and save information about the lock in the checkpoint-image.
> A follow-on patch will use this informaiton to restore the file-locks.
>
> Changelog[v4]:
> [Oren Laadan]: For consistency with other such objects, replace
> the "marker lock" checkpoint with a checkpoint of a count of the
> file-locks before the first file-lock of each file.
>
> Changelog[v3]:
> [Oren Laadan] Add a missing (loff_t) type cast and use a macro
> to set the marker/dummy file lock
>
> Changelog[v2]:
> [Matt Helsley]: Use fixed sizes (__s64) instead of 'loff_t' in
> 'struct ckpt_hdr_file_lock'.
> [Matt Helsley, Serge Hallyn]: Highlight new use of BKL (using
> lock_flocks() macros as suggested by Serge).
> [Matt Helsley]: Reorg code a bit to simplify error handling.
> [Matt Helsley]: Reorg code to initialize marker-lock (Pass a
> NULL lock to checkpoint_one_lock() to indicate marker).
>
> Signed-off-by: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
> ---
> fs/checkpoint.c | 142 ++++++++++++++++++++++++++++++++++++----
> include/linux/checkpoint_hdr.h | 17 +++++
> 2 files changed, 146 insertions(+), 13 deletions(-)
>
> diff --git a/fs/checkpoint.c b/fs/checkpoint.c
> index be9d39a..47aa802 100644
> --- a/fs/checkpoint.c
> +++ b/fs/checkpoint.c
> @@ -26,8 +26,19 @@
> #include <linux/checkpoint.h>
> #include <linux/eventpoll.h>
> #include <linux/eventfd.h>
> +#include <linux/smp_lock.h>
> #include <net/sock.h>
>
> +/*
> + * TODO: This code uses the BKL for consistency with other uses of
> + * 'for_each_lock()'. But since the BKL may be replaced with another
> + * lock in the future, use lock_flocks() macros instead. lock_flocks()
> + * are currently used in BKL-fix sand boxes and when those changes
> + * are merged, the following macros can be removed
> + */
> +#define lock_flocks() lock_kernel()
> +#define unlock_flocks() unlock_kernel()
> +
> /**************************************************************************
> * Checkpoint
> */
> @@ -256,8 +267,120 @@ static int checkpoint_file(struct ckpt_ctx *ctx, void *ptr)
> return ret;
> }
>
> +static int checkpoint_one_file_lock(struct ckpt_ctx *ctx,
> + struct file_lock *lock)
> +{
> + int rc;
> + struct ckpt_hdr_file_lock *h;
> +
> + if (!IS_POSIX(lock)) {
> + /* Hmm, we should have caught this while counting locks */
> + return -EBADF;
> + }
> +
> + h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_FILE_LOCK);
> + if (!h)
> + return -ENOMEM;
> +
> + h->fl_start = lock->fl_start;
> + h->fl_end = lock->fl_end;
> + h->fl_type = lock->fl_type;
> + h->fl_flags = lock->fl_flags;
> +
> + rc = ckpt_write_obj(ctx, &h->h);
> +
> + ckpt_hdr_put(ctx, h);
> +
> + return rc;
> +}
> +
> +static int checkpoint_file_lock_count(struct ckpt_ctx *ctx, int num_locks)
> +{
> + int rc;
> + struct ckpt_hdr_file_lock_count *h;
> +
> + h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_FILE_LOCK_COUNT);
> + if (!h)
> + return -ENOMEM;
> +
> + h->nr_locks = num_locks;
> +
> + rc = ckpt_write_obj(ctx, &h->h);
> +
> + ckpt_hdr_put(ctx, h);
> +
> + return rc;
> +}
> +
> +int
> +checkpoint_file_locks(struct ckpt_ctx *ctx, struct files_struct *files,
> + struct file *file)
> +{
> + int n;
> + int rc;
> + struct inode *inode;
> + struct file_lock **lockpp;
> + struct file_lock *lockp;
> +
> + lock_flocks();
> +
> + /*
> + * First count the number of file-locks on this file
> + */
> + n = 0;
> + rc = -EBADF;
> + inode = file->f_path.dentry->d_inode;
> + for_each_lock(inode, lockpp) {
> + lockp = *lockpp;
> + if (lockp->fl_owner != files)
> + continue;
> +
> + ckpt_debug("Lock [%lld, %lld, %d, 0x%x]\n", lockp->fl_start,
> + lockp->fl_end, lockp->fl_type, lockp->fl_flags);
> +
> + if (lockp->fl_owner != files)
> + continue;
> +
> + if (IS_POSIX(lockp))
> + n++;
> + else {
> + ckpt_err(ctx, rc, "%(T), checkpoint of lock "
> + "[%lld, %lld, %d, 0x%x] failed\n",
> + lockp->fl_start, lockp->fl_end,
> + lockp->fl_type, lockp->fl_flags);
> + goto out;
> + }
> + }
> +
> + /*
> + * Checkpoint the count of file-locks
> + */
> + rc = checkpoint_file_lock_count(ctx, n);
> + if (rc < 0) {
> + ckpt_err(ctx, rc, "%(T), checkpoint file-lock count failed\n");
> + goto out;
> + }
> +
> + /*
> + * Make a second pass and checkpoint file-locks themselves.
> + */
> + for_each_lock(inode, lockpp) {
> + lockp = *lockpp;
> + if (lockp->fl_owner != files)
> + continue;
> +
> + rc = checkpoint_one_file_lock(ctx, lockp);
> + if (rc < 0)
> + goto out;
> + }
> +
> +out:
> + unlock_flocks();
> + return rc;
> +}
> +
> /**
> - * ckpt_write_file_desc - dump the state of a given file descriptor
> + * checkpoint_file_desc - dump the state of a given file descriptor
> * @ctx: checkpoint context
> * @files: files_struct pointer
> * @fd: file descriptor
> @@ -288,18 +411,6 @@ static int checkpoint_file_desc(struct ckpt_ctx *ctx,
> }
> rcu_read_unlock();
>
> - ret = find_locks_with_owner(file, files);
> - /*
> - * find_locks_with_owner() returns an error when there
> - * are no locks found, so we *want* it to return an error
> - * code. Its success means we have to fail the checkpoint.
> - */
> - if (!ret) {
> - ret = -EBADF;
> - ckpt_err(ctx, ret, "%(T)fd %d has file lock or lease\n", fd);
> - goto out;
> - }
> -
> /* sanity check (although this shouldn't happen) */
> ret = -EBADF;
> if (!file) {
> @@ -323,6 +434,11 @@ static int checkpoint_file_desc(struct ckpt_ctx *ctx,
> h->fd_close_on_exec = coe;
>
> ret = ckpt_write_obj(ctx, &h->h);
> + if (ret < 0)
> + goto out;
> +
> + ret = checkpoint_file_locks(ctx, files, file);
> +
> out:
> ckpt_hdr_put(ctx, h);
> if (file)
> diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
> index 0381019..14b287f 100644
> --- a/include/linux/checkpoint_hdr.h
> +++ b/include/linux/checkpoint_hdr.h
> @@ -144,6 +144,10 @@ enum {
> #define CKPT_HDR_TTY_LDISC CKPT_HDR_TTY_LDISC
> CKPT_HDR_EPOLL_ITEMS, /* must be after file-table */
> #define CKPT_HDR_EPOLL_ITEMS CKPT_HDR_EPOLL_ITEMS
> + CKPT_HDR_FILE_LOCK_COUNT,
> +#define CKPT_HDR_FILE_LOCK_COUNT CKPT_HDR_FILE_LOCK_COUNT
> + CKPT_HDR_FILE_LOCK,
> +#define CKPT_HDR_FILE_LOCK CKPT_HDR_FILE_LOCK
>
> CKPT_HDR_MM = 401,
> #define CKPT_HDR_MM CKPT_HDR_MM
> @@ -586,6 +590,19 @@ struct ckpt_hdr_file_generic {
> struct ckpt_hdr_file common;
> } __attribute__((aligned(8)));
>
> +struct ckpt_hdr_file_lock_count {
> + struct ckpt_hdr h;
> + __u32 nr_locks;
> +};
> +
> +struct ckpt_hdr_file_lock {
> + struct ckpt_hdr h;
> + __s64 fl_start;
> + __s64 fl_end;
> + __u8 fl_type;
> + __u8 fl_flags;
> +};
> +
You forgot to add "__attribute__((aligned(8)));".
[maybe picking.. but-] Giving a "whole" object per lock seems
wasteful; I was hoping for something similar to how we do the
'struct ckpt_hdr_sigpending', e.g.
struct ckpt_file_lock {
__s64 fl_start;
__s64 fl_end;
__u8 fl_type;
__u8 fl_flags;
} __attribute__((aligned(8)));
struct ckpt_hdr_file_locks {
struct ckpt_hdr h;
__u32 nr_locks;
struct ckpt_file_lock locks[0];
} __attribute__((aligned(8)));
You could use ckpt_write_obj_type() with null pointer, and then
follow with the payload in chunks in the loop in checkpoint_file_locks()
Makes sense ?
Oren.
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