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<[email protected]>
>
> Patch:
> diff -uNp linux-2.6.12/fs/reiserfs/file.c
> linux-2.6.12-new/fs/reiserfs/file.c
>
--- linux-2.6.12/fs/reiserfs/file.c 2005-06-23 14:59:27.000000000 -0400
+++ linux-2.6.12-new/fs/reiserfs/file.c 2005-06-23 15:34:49.000000000 -0400
@@ -1306,7 +1306,7 @@ static ssize_t reiserfs_file_write( stru
so that nobody else can access these until we are done.
We get number of actual blocks needed as a result.*/
blocks_to_allocate = reiserfs_prepare_file_region_for_write(inode, pos, num_pages, write_bytes, prepared_pages);
- if ( blocks_to_allocate < 0 ) {
+ if ( IS_ERROR((const void *)blocks_to_allocate) ) {
res = blocks_to_allocate;
reiserfs_release_claimed_blocks(inode->i_sb, num_pages << (PAGE_CACHE_SHIFT - inode->i_blkbits));
break;
@@ -1363,6 +1363,10 @@ static ssize_t reiserfs_file_write( stru
}
}
+ /* If nothing is written, no need(actually, mustn't) to sync pages, just return res */
+ if( already_written == 0 )
+ goto out;
+
if ((file->f_flags & O_SYNC) || IS_SYNC(inode))
res = generic_osync_inode(inode, file->f_mapping, OSYNC_METADATA|OSYNC_DATA);
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