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splice: __generic_file_splice_read: fix i_size_read() length checks 

__generic_file_splice_read's partial page check, at eof after readpage,
not only got its calculations wrong, but also reused the loff variable:
causing data corruption when splicing from a non-0 offset in the file's
last page (revealed by ext2 -b 1024 testing on a loop of a tmpfs file).

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Hugh Dickins 2007-06-07 09:36:00 +02:00 committed by Jens Axboe
parent 20d698db67
commit 475ecade68
1 changed files with 10 additions and 8 deletions
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18
fs/splice.c
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@ -272,7 +272,6 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
struct page *page;
pgoff_t index, end_index;
loff_t isize;
size_t total_len;
int error, page_nr;
struct splice_pipe_desc spd = {
.pages = pages,
@ -298,7 +297,6 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
* Now fill in the holes:
*/
error = 0;
total_len = 0;
/*
* Lookup the (hopefully) full range of pages we need.
@ -429,29 +427,33 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
* the length and stop
*/
if (end_index == index) {
loff = PAGE_CACHE_SIZE - (isize & ~PAGE_CACHE_MASK);
if (total_len + loff > isize)
unsigned int plen;
/*
* max good bytes in this page
*/
plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
if (plen <= loff)
break;
/*
* force quit after adding this page
*/
this_len = min(this_len, plen - loff);
len = this_len;
this_len = min(this_len, loff);
loff = 0;
}
}
fill_it:
partial[page_nr].offset = loff;
partial[page_nr].len = this_len;
len -= this_len;
total_len += this_len;
loff = 0;
spd.nr_pages++;
index++;
}
/*
* Release any pages at the end, if we quit early. 'i' is how far
* Release any pages at the end, if we quit early. 'page_nr' is how far
* we got, 'nr_pages' is how many pages are in the map.
*/
while (page_nr < nr_pages)