linux-kernel - Re: [RFC][PATCH 4/8] file c/r: expose functions to query fs support

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Message-ID: <20090227211408.GB19872@us.ibm.com>
Date:	Fri, 27 Feb 2009 13:14:08 -0800
From:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	containers <containers@...ts.linux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	Oren Laadan <orenl@...columbia.edu>,
	Alexey Dobriyan <adobriyan@...il.com>, hch@...radead.org
Subject: Re: [RFC][PATCH 4/8] file c/r: expose functions to query fs support

Dave Hansen [dave@...ux.vnet.ibm.com] wrote:
| 
| This pair of functions will check to see whether a given
| 'struct file' can be checkpointed.  If it can't be, the
| "explain" function can also give a description why.
| 
| Signed-off-by: Dave Hansen <dave@...ux.vnet.ibm.com>
| ---
| 
|  linux-2.6.git-dave/checkpoint/ckpt_file.c     |   46 ++++++++++++++++++++++++++
|  linux-2.6.git-dave/include/linux/checkpoint.h |   18 ++++++++++
|  2 files changed, 64 insertions(+)
| 
| diff -puN checkpoint/ckpt_file.c~cr-explain-unckpt-file checkpoint/ckpt_file.c
| --- linux-2.6.git/checkpoint/ckpt_file.c~cr-explain-unckpt-file	2009-02-27 12:07:38.000000000 -0800
| +++ linux-2.6.git-dave/checkpoint/ckpt_file.c	2009-02-27 12:07:38.000000000 -0800
| @@ -72,6 +72,52 @@ int cr_scan_fds(struct files_struct *fil
|  	return n;
|  }
| 
| +int fs_is_cr_able(struct file_system_type *fs_type)
| +{
| +	if (fs_type->fs_flags & FS_CHECKPOINTABLE)
| +		return 1;
| +	/*
| +	 * We assume that all block-based filesystems that
| +	 * need devices work.  This covers all of the
| +	 * "important" fs's by default like ext*.  If this
| +	 * assumption becomes untrue, we may need a
| +	 * NOT_CHECKPOINTABLE flag in the future
| +	 */
| +	if (fs_type->fs_flags & FS_REQUIRES_DEV)
| +		return 1;
| +	return 0;
| +}
| +
| +int cr_explain_file(struct file *file, char *explain, int left)
| +{
| +	struct inode *inode = file->f_dentry->d_inode;
| +	struct file_system_type *fs_type = inode->i_sb->s_type;
| +
| +	if (!fs_is_cr_able(fs_type))
| +		return snprintf(explain, left,
| +				" (%s does not support checkpoint)",
| +				fs_type->name);
| +
| +	if (special_file(inode->i_mode))
| +		return snprintf(explain, left, " (special file)");
| +
| +	return 0;
| +}
| +
| +int cr_file_supported(struct file *file)
| +{
| +	struct inode *inode = file->f_dentry->d_inode;
| +	struct file_system_type *fs_type = inode->i_sb->s_type;
| +
| +	if (fs_is_cr_able(fs_type))
| +		return 0;

Should this be if (!fs_is_cr_able(fs_type)) ?

| +
| +	if (special_file(inode->i_mode))
| +		return 0;
| +
| +	return 1;
| +}
| +
|  /* 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)
|  {
| diff -puN include/linux/checkpoint.h~cr-explain-unckpt-file include/linux/checkpoint.h
| --- linux-2.6.git/include/linux/checkpoint.h~cr-explain-unckpt-file	2009-02-27 12:07:38.000000000 -0800
| +++ linux-2.6.git-dave/include/linux/checkpoint.h	2009-02-27 12:07:38.000000000 -0800
| @@ -13,6 +13,8 @@
|  #include <linux/path.h>
|  #include <linux/fs.h>
| 
| +#ifdef CONFIG_CHECKPOINT_RESTART
| +
|  #define CR_VERSION  2
| 
|  struct cr_ctx {
| @@ -99,4 +101,20 @@ extern int cr_read_files(struct cr_ctx *
| 
|  #define pr_fmt(fmt) "[%d:c/r:%s] " fmt, task_pid_vnr(current), __func__
| 
| +int cr_explain_file(struct file *file, char *explain, int left);
| +int cr_file_supported(struct file *file);
| +
| +#else /* !CONFIG_CHECKPOINT_RESTART */
| +
| +static inline int cr_explain_file(struct file *file, char *explain, int left)
| +{
| +	return 0;
| +}
| +
| +int cr_file_supported(struct file *file)
| +{
| +	return 0;
| +}
| +
| +#endif /* CONFIG_CHECKPOINT_RESTART */
|  #endif /* _CHECKPOINT_CKPT_H_ */
| _
| --
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