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Commit e8b96eb5 authored by Eric Sandeen's avatar Eric Sandeen Committed by Al Viro
Browse files

vfs: allow custom EOF in generic_file_llseek code 



For ext3/4 htree directories, using the vfs llseek function with
SEEK_END goes to i_size like for any other file, but in reality
we want the maximum possible hash value.  Recent changes
in ext4 have cut & pasted generic_file_llseek() back into fs/ext4/dir.c,
but replicating this core code seems like a bad idea, especially
since the copy has already diverged from the vfs.

This patch updates generic_file_llseek_size to accept
both a custom maximum offset, and a custom EOF position.  With this
in place, ext4_dir_llseek can pass in the appropriate maximum hash
position for both maxsize and eof, and get what it wants.

As far as I know, this does not fix any bugs - nfs in the kernel
doesn't use SEEK_END, and I don't know of any user who does.  But
some ext4 folks seem keen on doing the right thing here, and I can't
really argue.

(Patch also fixes up some comments slightly)

Signed-off-by: default avatarEric Sandeen <sandeen@redhat.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 4ea425b6

fs/ext3/dir.c

+2 −1
Original line number Diff line number Diff line
@@ -303,7 +303,8 @@ loff_t ext3_dir_llseek(struct file *file, loff_t offset, int origin) 


	if (likely(dx_dir))

		return generic_file_llseek_size(file, offset, origin,

					        ext3_get_htree_eof(file));

					        ext3_get_htree_eof(file),

						i_size_read(inode));

	else

		return generic_file_llseek(file, offset, origin);

}

fs/ext4/file.c

+2 −1
Original line number Diff line number Diff line
@@ -225,7 +225,8 @@ loff_t ext4_llseek(struct file *file, loff_t offset, int origin) 
	else

		maxbytes = inode->i_sb->s_maxbytes;



	return generic_file_llseek_size(file, offset, origin, maxbytes);

	return generic_file_llseek_size(file, offset, origin,

					maxbytes, i_size_read(inode));

}



const struct file_operations ext4_file_operations = {

fs/read_write.c

+10 −8
Original line number Diff line number Diff line
@@ -55,10 +55,11 @@ static loff_t lseek_execute(struct file *file, struct inode *inode, 
 * @file:	file structure to seek on

 * @offset:	file offset to seek to

 * @origin:	type of seek

 * @size:	max size of file system

 * @size:	max size of this file in file system

 * @eof:	offset used for SEEK_END position

 *

 * This is a variant of generic_file_llseek that allows passing in a custom

 * file size.

 * maximum file size and a custom EOF position, for e.g. hashed directories

 *

 * Synchronization:

 * SEEK_SET and SEEK_END are unsynchronized (but atomic on 64bit platforms)
@@ -67,13 +68,13 @@ static loff_t lseek_execute(struct file *file, struct inode *inode, 
 */

loff_t

generic_file_llseek_size(struct file *file, loff_t offset, int origin,

		loff_t maxsize)

		loff_t maxsize, loff_t eof)

{

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



	switch (origin) {

	case SEEK_END:

		offset += i_size_read(inode);

		offset += eof;

		break;

	case SEEK_CUR:

		/*
@@ -99,7 +100,7 @@ generic_file_llseek_size(struct file *file, loff_t offset, int origin, 
		 * In the generic case the entire file is data, so as long as

		 * offset isn't at the end of the file then the offset is data.

		 */

		if (offset >= i_size_read(inode))

		if (offset >= eof)

			return -ENXIO;

		break;

	case SEEK_HOLE:
@@ -107,9 +108,9 @@ generic_file_llseek_size(struct file *file, loff_t offset, int origin, 
		 * There is a virtual hole at the end of the file, so as long as

		 * offset isn't i_size or larger, return i_size.

		 */

		if (offset >= i_size_read(inode))

		if (offset >= eof)

			return -ENXIO;

		offset = i_size_read(inode);

		offset = eof;

		break;

	}
@@ -132,7 +133,8 @@ loff_t generic_file_llseek(struct file *file, loff_t offset, int origin) 
	struct inode *inode = file->f_mapping->host;



	return generic_file_llseek_size(file, offset, origin,

					inode->i_sb->s_maxbytes);

					inode->i_sb->s_maxbytes,

					i_size_read(inode));

}

EXPORT_SYMBOL(generic_file_llseek);

include/linux/fs.h

+1 −1
Original line number Diff line number Diff line
@@ -2454,7 +2454,7 @@ extern loff_t noop_llseek(struct file *file, loff_t offset, int origin); 
extern loff_t no_llseek(struct file *file, loff_t offset, int origin);

extern loff_t generic_file_llseek(struct file *file, loff_t offset, int origin);

extern loff_t generic_file_llseek_size(struct file *file, loff_t offset,

		int origin, loff_t maxsize);

		int origin, loff_t maxsize, loff_t eof);

extern int generic_file_open(struct inode * inode, struct file * filp);

extern int nonseekable_open(struct inode * inode, struct file * filp);