hi, all, in the previous patch, i accidentally typed several 
'dd(vim)'

Sorry

> Related FS:
>     ReiserFS
> 
> Related Files:
>     fs/reiserfs/file.c
> 
> Bug description:
>     Make a ReiserFS partition in USB storage HDD, create a test file
> with enough size.
>     Write a program, do: open(O_SYNC/O_DSYNC) - read - close. After
> each
> operation, pause for a while, such as 3s. Between open and read, unlug
> the USB wire. open returns zero-filled buffer, no error returns.
> 
> Bug analysis:
>     reiserfs_file_write will claim some blocks, commit the I/O
> request,
> if O_SYNC and O_DSYNC is used, it will
>     if ((file->f_flags & O_SYNC) || IS_SYNC(inode))
>         res = generic_osync_inode(inode, file->f_mapping,
>                                   OSYNC_METADATA|OSYNC_DATA);
> The question is, if I/O error occurs,       
>         res = reiserfs_allocate_blocks_for_region fails with -EIO, so
> it will exit the loop, no I/O request, no page marked as dirty.
> If run generic_osync_inode, it returns 0(no dirty page), res will be
> overwritten from -EIO to 0, thus no error report.
> 
> Also,  reiserfs_file_write contains a serious bug, see here
>         blocks_to_allocate = reiserfs_prepare_file_region_for_write
>                 (inode, pos, num_pages, write_bytes, prepared_pages);
> Here blocks_to_allocate is defined as size_t, i.e. unsigned int, but
> reiserfs_prepare_file_region_for_write is declared as int, so
> sometimes
> it will return -EIO, -ENOENT, etc, take a look at this line
>         if ( blocks_to_allocate < 0 ) { <- This will never happen
>             res = blocks_to_allocate;
>             reiserfs_release_claimed_blocks(inode->i_sb, 
>                 num_pages << (PAGE_CACHE_SHIFT - inode->i_blkbits));
>             break;
>         }
> 
> Way around:
> 1) if already_written is zero, don't do generic_osync_inode
> 2) tell the result of reiserfs_prepare_file_region_for_write with
> IS_ERR
>    macro or cast it to size_t
> 
> Signed-off-by: Qu Fuping<fs@ercist.iscas.ac.cn>
> 
> Patch:
> diff -uNp linux-2.6.12/fs/reiserfs/file.c
> linux-2.6.12-new/fs/reiserfs/file.c
>