mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-18 10:13:57 +08:00
81b0c87133
The recent generic_file_write() deadlock fix caused generic_file_buffered_write() to loop inifinitely when presented with a zero-length iovec segment. Fix. Note that this fix deliberately avoids calling ->prepare_write(), ->commit_write() etc with a zero-length write. This is because I don't trust all filesystems to get that right. This is a cautious approach, for 2.6.17.x. For 2.6.18 we should just go ahead and call ->prepare_write() and ->commit_write() with the zero length and fix any broken filesystems. So I'll make that change once this code is stabilised and backported into 2.6.17.x. The reason for preferring to call ->prepare_write() and ->commit_write() with the zero-length segment: a zero-length segment _should_ be sufficiently uncommon that this is the correct way of handling it. We don't want to optimise for poorly-written userspace at the expense of well-written userspace. Cc: "Vladimir V. Saveliev" <vs@namesys.com> Cc: Neil Brown <neilb@suse.de> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Chris Wright <chrisw@sous-sol.org> Cc: Greg KH <greg@kroah.com> Cc: <stable@kernel.org> Cc: walt <wa1ter@myrealbox.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
105 lines
2.8 KiB
C
105 lines
2.8 KiB
C
/*
|
|
* linux/mm/filemap.h
|
|
*
|
|
* Copyright (C) 1994-1999 Linus Torvalds
|
|
*/
|
|
|
|
#ifndef __FILEMAP_H
|
|
#define __FILEMAP_H
|
|
|
|
#include <linux/types.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/highmem.h>
|
|
#include <linux/uio.h>
|
|
#include <linux/config.h>
|
|
#include <linux/uaccess.h>
|
|
|
|
size_t
|
|
__filemap_copy_from_user_iovec_inatomic(char *vaddr,
|
|
const struct iovec *iov,
|
|
size_t base,
|
|
size_t bytes);
|
|
|
|
/*
|
|
* Copy as much as we can into the page and return the number of bytes which
|
|
* were sucessfully copied. If a fault is encountered then clear the page
|
|
* out to (offset+bytes) and return the number of bytes which were copied.
|
|
*
|
|
* NOTE: For this to work reliably we really want copy_from_user_inatomic_nocache
|
|
* to *NOT* zero any tail of the buffer that it failed to copy. If it does,
|
|
* and if the following non-atomic copy succeeds, then there is a small window
|
|
* where the target page contains neither the data before the write, nor the
|
|
* data after the write (it contains zero). A read at this time will see
|
|
* data that is inconsistent with any ordering of the read and the write.
|
|
* (This has been detected in practice).
|
|
*/
|
|
static inline size_t
|
|
filemap_copy_from_user(struct page *page, unsigned long offset,
|
|
const char __user *buf, unsigned bytes)
|
|
{
|
|
char *kaddr;
|
|
int left;
|
|
|
|
kaddr = kmap_atomic(page, KM_USER0);
|
|
left = __copy_from_user_inatomic_nocache(kaddr + offset, buf, bytes);
|
|
kunmap_atomic(kaddr, KM_USER0);
|
|
|
|
if (left != 0) {
|
|
/* Do it the slow way */
|
|
kaddr = kmap(page);
|
|
left = __copy_from_user_nocache(kaddr + offset, buf, bytes);
|
|
kunmap(page);
|
|
}
|
|
return bytes - left;
|
|
}
|
|
|
|
/*
|
|
* This has the same sideeffects and return value as filemap_copy_from_user().
|
|
* The difference is that on a fault we need to memset the remainder of the
|
|
* page (out to offset+bytes), to emulate filemap_copy_from_user()'s
|
|
* single-segment behaviour.
|
|
*/
|
|
static inline size_t
|
|
filemap_copy_from_user_iovec(struct page *page, unsigned long offset,
|
|
const struct iovec *iov, size_t base, size_t bytes)
|
|
{
|
|
char *kaddr;
|
|
size_t copied;
|
|
|
|
kaddr = kmap_atomic(page, KM_USER0);
|
|
copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,
|
|
base, bytes);
|
|
kunmap_atomic(kaddr, KM_USER0);
|
|
if (copied != bytes) {
|
|
kaddr = kmap(page);
|
|
copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,
|
|
base, bytes);
|
|
if (bytes - copied)
|
|
memset(kaddr + offset + copied, 0, bytes - copied);
|
|
kunmap(page);
|
|
}
|
|
return copied;
|
|
}
|
|
|
|
static inline void
|
|
filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes)
|
|
{
|
|
const struct iovec *iov = *iovp;
|
|
size_t base = *basep;
|
|
|
|
do {
|
|
int copy = min(bytes, iov->iov_len - base);
|
|
|
|
bytes -= copy;
|
|
base += copy;
|
|
if (iov->iov_len == base) {
|
|
iov++;
|
|
base = 0;
|
|
}
|
|
} while (bytes);
|
|
*iovp = iov;
|
|
*basep = base;
|
|
}
|
|
#endif
|