Skip to contentSkip to conversation

ReiserFS file.c several bug-fix - modified version

PATCH RESEND New fs 1 participant 1 message Jun 23, 2005 VFS

lore
Share & tools
lore

fs

author
#0 lore raw

PATCH RESEND 1/1 ReiserFS file.c several bug-fix - modified version

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

Sorry

Quoted 47 lines

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

Quoted 6 lines
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

fs/reiserfs/file.c +5 -1
@@ -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);