Commit ac13a829 authored by Fabian Frederick's avatar Fabian Frederick Committed by Linus Torvalds
Browse files

fs/libfs.c: add generic data flush to fsync 



Description by Jan Kara:
 "A lot of older filesystems don't properly flush volatile disk caches
  on fsync(2) which can lead to loss of fsynced data after power failure.

This patch makes generic_file_fsync() issue proper cache flush to fix the
problem.  Sysadmin can use /sys/devices/.../cache_type to tell the system
it should not send the cache flush."

[akpm@linux-foundation.org: nuke ifdef]
[akpm@linux-foundation.org: fix warning]
Signed-off-by: default avatarFabian Frederick <fabf@skynet.be>
Suggested-by: default avatarJan Kara <jack@suse.cz>
Suggested-by: default avatarChristoph Hellwig <hch@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fd2916bd

fs/libfs.c

+31 −3
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 
 *	Library for filesystems writers.

 */



#include <linux/blkdev.h>

#include <linux/export.h>

#include <linux/pagemap.h>

#include <linux/slab.h>
@@ -923,15 +924,18 @@ struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid, 
EXPORT_SYMBOL_GPL(generic_fh_to_parent);



/**

 * generic_file_fsync - generic fsync implementation for simple filesystems

 * __generic_file_fsync - generic fsync implementation for simple filesystems

 *

 * @file:	file to synchronize

 * @start:	start offset in bytes

 * @end:	end offset in bytes (inclusive)

 * @datasync:	only synchronize essential metadata if true

 *

 * This is a generic implementation of the fsync method for simple

 * filesystems which track all non-inode metadata in the buffers list

 * hanging off the address_space structure.

 */

int generic_file_fsync(struct file *file, loff_t start, loff_t end,

int __generic_file_fsync(struct file *file, loff_t start, loff_t end,

				 int datasync)

{

	struct inode *inode = file->f_mapping->host;
@@ -952,10 +956,34 @@ int generic_file_fsync(struct file *file, loff_t start, loff_t end, 
	err = sync_inode_metadata(inode, 1);

	if (ret == 0)

		ret = err;



out:

	mutex_unlock(&inode->i_mutex);

	return ret;

}

EXPORT_SYMBOL(__generic_file_fsync);



/**

 * generic_file_fsync - generic fsync implementation for simple filesystems

 *			with flush

 * @file:	file to synchronize

 * @start:	start offset in bytes

 * @end:	end offset in bytes (inclusive)

 * @datasync:	only synchronize essential metadata if true

 *

 */



int generic_file_fsync(struct file *file, loff_t start, loff_t end,

		       int datasync)

{

	struct inode *inode = file->f_mapping->host;

	int err;



	err = __generic_file_fsync(file, start, end, datasync);

	if (err)

		return err;

	return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);

}

EXPORT_SYMBOL(generic_file_fsync);



/**

include/linux/blkdev.h

+9 −0
Original line number Diff line number Diff line
@@ -1607,6 +1607,9 @@ struct block_device_operations { 
extern int __blkdev_driver_ioctl(struct block_device *, fmode_t, unsigned int,

				 unsigned long);

#else /* CONFIG_BLOCK */



struct block_device;



/*

 * stubs for when the block layer is configured out

 */
@@ -1642,6 +1645,12 @@ static inline bool blk_needs_flush_plug(struct task_struct *tsk) 
	return false;

}



static inline int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask,

				     sector_t *error_sector)

{

	return 0;

}



#endif /* CONFIG_BLOCK */



#endif

include/linux/fs.h

+1 −0
Original line number Diff line number Diff line
@@ -2590,6 +2590,7 @@ extern ssize_t simple_read_from_buffer(void __user *to, size_t count, 
extern ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,

		const void __user *from, size_t count);



extern int __generic_file_fsync(struct file *, loff_t, loff_t, int);

extern int generic_file_fsync(struct file *, loff_t, loff_t, int);



extern int generic_check_addressable(unsigned, u64);

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