/*
* linux/mm/filemap.c
*
* Copyright (C) 1994, 1995 Linus Torvalds
*/
/*
* This file handles the generic file mmap semantics used by
* most "normal" filesystems (but you don't /have/ to use this:
* the NFS filesystem does this differently, for example)
*/
#include <linux/stat.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/shm.h>
#include <linux/errno.h>
#include <linux/mman.h>
#include <linux/string.h>
#include <linux/malloc.h>
#include <linux/fs.h>
#include <linux/locks.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <asm/segment.h>
#include <asm/system.h>
#include <asm/pgtable.h>
/*
* Shared mappings implemented 30.11.1994. It's not fully working yet,
* though.
*
* Shared mappings now work. 15.8.1995 Bruno.
*/
unsigned long page_cache_size = 0;
struct page * page_hash_table[PAGE_HASH_SIZE];
/*
* Simple routines for both non-shared and shared mappings.
*/
#define release_page(page) __free_page((page))
/*
* Invalidate the pages of an inode, removing all pages that aren't
* locked down (those are sure to be up-to-date anyway, so we shouldn't
* invalidate them).
*/
void invalidate_inode_pages(struct inode * inode)
/* Usuwanie stron należących do inode, nie będących zablokowanymi */
{
struct page ** p;
struct page * page;
p = &inode->i_pages;
while ((page = *p) != NULL) /* dopóki są jeszcze strony */
if (PageLocked(page)) {/* zablokowana */
p = &page->next;
continue;
}
inode->i_nrpages--;
/* reorganizujemy listę */
if ((*p = page->next) != NULL)
(*p)->prev = page->prev;
page->dirty = 0;
page->next = NULL;
page->prev = NULL;
/* usuwamy z kolejki haszującej */
remove_page_from_hash_queue(page);
page->inode = NULL;
/* zwalniamy */
__free_page(page);
continue;
}
}
/*
* Truncate the page cache at a set offset, removing the pages
* that are beyond that offset (and zeroing out partial pages).
*/
void truncate_inode_pages(struct inode * inode, unsigned long start)
/* skracanie cache'u stron do offsetu "start"
strony za tym offsetem są usuwane */
{
struct page ** p;
struct page * page;
repeat:
p = &inode->i_pages;
while ((page = *p) != NULL) {
unsigned long offset = page->offset;
/* page wholly truncated - free it */
if (offset >= start) {
if (PageLocked(page)) {
__wait_on_page(page);
goto repeat;
}
inode->i_nrpages--;
if ((*p = page->next) != NULL)
(*p)->prev = page->prev;
page->dirty = 0;
page->next = NULL;
page->prev = NULL;
remove_page_from_hash_queue(page);
page->inode = NULL;
__free_page(page);
continue;
}
p = &page->next;
offset = start - offset;
/* partial truncate, clear end of page */
if (offset < PAGE_SIZE) {
unsigned long address = page_address(page);
memset((void *) (offset + address), 0, PAGE_SIZE - offset);
flush_page_to_ram(address);
}
}
}
int shrink_mmap(int priority, int dma, int free_buf)
/* staramy się odebrać jakąś ramkę */
{
/* zmienna clock powoduje, że przeszukiwanie obszaru zaczynamy od
miejsca w którym ostatnio skończyliśmy */
static int clock = 0;
struct page * page;
unsigned long limit = MAP_NR(high_memory);
struct buffer_head *tmp, *bh;
int count_max, count_min;
count_max = (limit<<1) >> (priority>>1);
count_min = (limit<<1) >> (priority);
page = mem_map + clock; /* początek przeszukiwania */
do {
count_max--;
if (page->inode || page->buffers)
count_min--;
if (PageLocked(page)) /* zablokowana */
goto next; /* następna strona */
if (dma && !PageDMA(page)) /* nie można przesłać przez DMA */
goto next; /* następna strona */
/* First of all, regenerate the page's referenced bit
from any buffers in the page */
bh = page->buffers;
if(bh) { /* strona ma bufory */
tmp = bh;
{ /* dla wszystkich buforow */
if (buffer_touched(tmp)) {
clear_bit(BH_Touched, &tmp->b_state);
set_bit(PG_referenced, &page->flags);
}
tmp = tmp->b_this_page;
} while (tmp != bh);
}
/* We can't throw away shared pages, but we do mark
them as referenced. This relies on the fact that
no page is currently in both the page cache and the
buffer cache; we'd have to modify the following
test to allow for that case. */
switch (page->count) {/*count-liczba procesów korzystających
z tej strony */
case 1:
/* If it has been referenced recently, don't free it */
if (clear_bit(PG_referenced, &page->flags)) {
/* age this page potential used */
if (priority < 4)
age_page(page);
break;
}
/* is it a page cache page? */
if (page->inode) {
remove_page_from_hash_queue(page);
remove_page_from_inode_queue(page);
__free_page(page);
return 1;
}
/* is it a buffer cache page? */
if (free_buf && bh && try_to_free_buffer(bh, &bh, 6))
return 1;
break;
default:
/* more than one users: we can't throw it away */
set_bit(PG_referenced, &page->flags);
/* fall through */
case 0:
/* nothing */
}
next:
page++;
clock++;
if (clock >= limit) {
clock = 0;
page = mem_map;
}
} while (count_max > 0 && count_min > 0);
return 0;
}
/*
* This is called from try_to_swap_out() when we try to get rid of some
* pages.. If we're unmapping the last occurrence of this page, we also
* free it from the page hash-queues etc, as we don't want to keep it
* in-core unnecessarily.
*/
unsigned long page_unuse(unsigned long page)
{
struct page * p = mem_map + MAP_NR(page);
int count = p->count;
if (count != 2)
return count;
if (!p->inode)
return count;
remove_page_from_hash_queue(p);
remove_page_from_inode_queue(p);
free_page(page);
return 1;
}
/*
* Update a page cache copy, when we're doing a "write()" system call
* See also "update_vm_cache()".
*/
void update_vm_cache(struct inode * inode, unsigned long pos, const char * buf, int count)
{
unsigned long offset, len;
offset = (pos & ~PAGE_MASK);
pos = pos & PAGE_MASK;
len = PAGE_SIZE - offset;
do {
struct page * page;
if (len > count)
len = count;
page = find_page(inode, pos);
if (page) {
wait_on_page(page);
memcpy((void *) (offset + page_address(page)), buf, len);
release_page(page);
}
count -= len;
buf += len;
len = PAGE_SIZE;
offset = 0;
pos += PAGE_SIZE;
} while (count);
}
static inline void add_to_page_cache(struct page * page,
struct inode * inode, unsigned long offset,
struct page **hash)
{
page->count++;
page->flags &= ~((1 << PG_uptodate) | (1 << PG_error));
page->offset = offset;
add_page_to_inode_queue(inode, page);
__add_page_to_hash_queue(page, hash);
}
/*
* Try to read ahead in the file. "page_cache" is a potentially free page
* that we could use for the cache (if it is 0 we can try to create one,
* this is all overlapped with the IO on the previous page finishing anyway)
*/
static unsigned long try_to_read_ahead(struct inode * inode, unsigned long offset, unsigned long page_cache)
{
struct page * page;
struct page ** hash;
offset &= PAGE_MASK;
switch (page_cache) {
case 0:
page_cache = __get_free_page(GFP_KERNEL);
if (!page_cache)
break;
default:
if (offset >= inode->i_size)
break;
hash = page_hash(inode, offset);
page = __find_page(inode, offset, *hash);
if (!page) {
/*
* Ok, add the new page to the hash-queues...
*/
page = mem_map + MAP_NR(page_cache);
add_to_page_cache(page, inode, offset, hash);
inode->i_op->readpage(inode, page);
page_cache = 0;
}
release_page(page);
}
return page_cache;
}
/*
* Wait for IO to complete on a locked page.
*
* This must be called with the caller "holding" the page,
* ie with increased "page->count" so that the page won't
* go away during the wait..
*/
void __wait_on_page(struct page *page)
{
struct wait_queue wait = { current, NULL };
add_wait_queue(&page->wait, &wait);
repeat:
run_task_queue(&tq_disk);
current->state = TASK_UNINTERRUPTIBLE;
if (PageLocked(page)) {
schedule();
goto repeat;
}
remove_wait_queue(&page->wait, &wait);
current->state = TASK_RUNNING;
}
#if 0
#define PROFILE_READAHEAD
#define DEBUG_READAHEAD
#endif
/*
* Read-ahead profiling information
* --------------------------------
* Every PROFILE_MAXREADCOUNT, the following information is written
* to the syslog:
* Percentage of asynchronous read-ahead.
* Average of read-ahead fields context value.
* If DEBUG_READAHEAD is defined, a snapshot of these fields is written
* to the syslog.
*/
#ifdef PROFILE_READAHEAD
#define PROFILE_MAXREADCOUNT 1000
static unsigned long total_reada;
static unsigned long total_async;
static unsigned long total_ramax;
static unsigned long total_ralen;
static unsigned long total_rawin;
static void profile_readahead(int async, struct file *filp)
{
unsigned long flags;
++total_reada;
if (async)
++total_async;
total_ramax += filp->f_ramax;
total_ralen += filp->f_ralen;
total_rawin += filp->f_rawin;
if (total_reada > PROFILE_MAXREADCOUNT) {
save_flags(flags);
cli();
if (!(total_reada > PROFILE_MAXREADCOUNT)) {
restore_flags(flags);
return;
}
printk("Readahead average: max=%ld, len=%ld, win=%ld, async=%ld%%\n",
total_ramax/total_reada,
total_ralen/total_reada,
total_rawin/total_reada,
(total_async*100)/total_reada);
#ifdef DEBUG_READAHEAD
printk("Readahead snapshot: max=%ld, len=%ld, win=%ld, raend=%ld\n",
filp->f_ramax, filp->f_ralen, filp->f_rawin, filp->f_raend);
#endif
total_reada = 0;
total_async = 0;
total_ramax = 0;
total_ralen = 0;
total_rawin = 0;
restore_flags(flags);
}
}
#endif /* defined PROFILE_READAHEAD */
/*
* Read-ahead context:
* -------------------
* The read ahead context fields of the "struct file" are the following:
* - f_raend : position of the first byte after the last page we tried to
* read ahead.
* - f_ramax : current read-ahead maximum size.
* - f_ralen : length of the current IO read block we tried to read-ahead.
* - f_rawin : length of the current read-ahead window.
* if last read-ahead was synchronous then
* f_rawin = f_ralen
* otherwise (was asynchronous)
* f_rawin = previous value of f_ralen + f_ralen
*
* Read-ahead limits:
* ------------------
* MIN_READAHEAD : minimum read-ahead size when read-ahead.
* MAX_READAHEAD : maximum read-ahead size when read-ahead.
*
* Synchronous read-ahead benefits:
* --------------------------------
* Using reasonable IO xfer length from peripheral devices increase system
* performances.
* Reasonable means, in this context, not too large but not too small.
* The actual maximum value is:
* MAX_READAHEAD + PAGE_SIZE = 76k is CONFIG_READA_SMALL is undefined
* and 32K if defined (4K page size assumed).
*
* Asynchronous read-ahead benefits:
* ---------------------------------
* Overlapping next read request and user process execution increase system
* performance.
*
* Read-ahead risks:
* -----------------
* We have to guess which further data are needed by the user process.
* If these data are often not really needed, it's bad for system
* performances.
* However, we know that files are often accessed sequentially by
* application programs and it seems that it is possible to have some good
* strategy in that guessing.
* We only try to read-ahead files that seems to be read sequentially.
*
* Asynchronous read-ahead risks:
* ------------------------------
* In order to maximize overlapping, we must start some asynchronous read
* request from the device, as soon as possible.
* We must be very careful about:
* - The number of effective pending IO read requests.
* ONE seems to be the only reasonable value.
* - The total memory pool usage for the file access stream.
* This maximum memory usage is implicitly 2 IO read chunks:
* 2*(MAX_READAHEAD + PAGE_SIZE) = 156K if CONFIG_READA_SMALL is undefined,
* 64k if defined (4K page size assumed).
*/
#define PageAlignSize(size) (((size) + PAGE_SIZE -1) & PAGE_MASK)
#ifdef CONFIG_READA_SMALL /* small readahead */
#define MAX_READAHEAD PageAlignSize(4096*7)
#define MIN_READAHEAD PageAlignSize(4096*2)
#else /* large readahead */
#define MAX_READAHEAD PageAlignSize(4096*18)
#define MIN_READAHEAD PageAlignSize(4096*3)
#endif
static inline unsigned long generic_file_readahead(int reada_ok, struct file * filp, struct inode * inode,
unsigned long ppos, struct page * page,
unsigned long page_cache)
{
unsigned long max_ahead, ahead;
unsigned long raend;
raend = filp->f_raend & PAGE_MASK;
max_ahead = 0;
/*
* The current page is locked.
* If the current position is inside the previous read IO request, do not
* try to reread previously read ahead pages.
* Otherwise decide or not to read ahead some pages synchronously.
* If we are not going to read ahead, set the read ahead context for this
* page only.
*/
if (PageLocked(page)) {
if (!filp->f_ralen || ppos >= raend || ppos + filp->f_ralen < raend) {
raend = ppos;
if (raend < inode->i_size)
max_ahead = filp->f_ramax;
filp->f_rawin = 0;
filp->f_ralen = PAGE_SIZE;
if (!max_ahead) {
filp->f_raend = ppos + filp->f_ralen;
filp->f_rawin += filp->f_ralen;
}
}
}
/*
* The current page is not locked.
* If we were reading ahead and,
* if the current max read ahead size is not zero and,
* if the current position is inside the last read-ahead IO request,
* it is the moment to try to read ahead asynchronously.
* We will later force unplug device in order to force asynchronous read IO.
*/
else if (reada_ok && filp->f_ramax && raend >= PAGE_SIZE &&
ppos <= raend && ppos + filp->f_ralen >= raend) {
/*
* Add ONE page to max_ahead in order to try to have about the same IO max size
* as synchronous read-ahead (MAX_READAHEAD + 1)*PAGE_SIZE.
* Compute the position of the last page we have tried to read in order to
* begin to read ahead just at the next page.
*/
raend -= PAGE_SIZE;
if (raend < inode->i_size)
max_ahead = filp->f_ramax + PAGE_SIZE;
if (max_ahead) {
filp->f_rawin = filp->f_ralen;
filp->f_ralen = 0;
reada_ok = 2;
}
}
/*
* Try to read ahead pages.
* We hope that ll_rw_blk() plug/unplug, coalescence, requests sort and the
* scheduler, will work enough for us to avoid too bad actuals IO requests.
*/
ahead = 0;
while (ahead < max_ahead) {
ahead += PAGE_SIZE;
page_cache = try_to_read_ahead(inode, raend + ahead, page_cache);
}
/*
* If we tried to read ahead some pages,
* If we tried to read ahead asynchronously,
* Try to force unplug of the device in order to start an asynchronous
* read IO request.
* Update the read-ahead context.
* Store the length of the current read-ahead window.
* Double the current max read ahead size.
* That heuristic avoid to do some large IO for files that are not really
* accessed sequentially.
*/
if (ahead) {
if (reada_ok == 2) {
run_task_queue(&tq_disk);
}
filp->f_ralen += ahead;
filp->f_rawin += filp->f_ralen;
filp->f_raend = raend + ahead + PAGE_SIZE;
filp->f_ramax += filp->f_ramax;
if (filp->f_ramax > MAX_READAHEAD)
filp->f_ramax = MAX_READAHEAD;
#ifdef PROFILE_READAHEAD
profile_readahead((reada_ok == 2), filp);
#endif
}
return page_cache;
}
/*
* This is a generic file read routine, and uses the
* inode->i_op->readpage() function for the actual low-level
* stuff.
*
* This is really ugly. But the goto's actually try to clarify some
* of the logic when it comes to error handling etc.
*/
int generic_file_read(struct inode * inode, struct file * filp, char * buf, int count)
{
int error, read;
unsigned long pos, ppos, page_cache;
int reada_ok;
error = 0;
read = 0;
page_cache = 0;
pos = filp->f_pos;
ppos = pos & PAGE_MASK;
/*
* If the current position is outside the previous read-ahead window,
* we reset the current read-ahead context and set read ahead max to zero
* (will be set to just needed value later),
* otherwise, we assume that the file accesses are sequential enough to
* continue read-ahead.
*/
if (ppos > filp->f_raend || ppos + filp->f_rawin < filp->f_raend) {
reada_ok = 0;
filp->f_raend = 0;
filp->f_ralen = 0;
filp->f_ramax = 0;
filp->f_rawin = 0;
} else {
reada_ok = 1;
}
/*
* Adjust the current value of read-ahead max.
* If the read operation stay in the first half page, force no readahead.
* Otherwise try to increase read ahead max just enough to do the read request.
* Then, at least MIN_READAHEAD if read ahead is ok,
* and at most MAX_READAHEAD in all cases.
*/
if (pos + count <= (PAGE_SIZE >> 1)) {
filp->f_ramax = 0;
} else {
unsigned long needed;
needed = ((pos + count) & PAGE_MASK) - ppos;
if (filp->f_ramax < needed)
filp->f_ramax = needed;
if (reada_ok && filp->f_ramax < MIN_READAHEAD)
filp->f_ramax = MIN_READAHEAD;
if (filp->f_ramax > MAX_READAHEAD)
filp->f_ramax = MAX_READAHEAD;
}
for (;;) {
struct page *page, **hash;
if (pos >= inode->i_size)
break;
/*
* Try to find the data in the page cache..
*/
hash = page_hash(inode, pos & PAGE_MASK);
page = __find_page(inode, pos & PAGE_MASK, *hash);
if (!page)
goto no_cached_page;
found_page:
/*
* Try to read ahead only if the current page is filled or being filled.
* Otherwise, if we were reading ahead, decrease max read ahead size to
* the minimum value.
* In this context, that seems to may happen only on some read error or if
* the page has been rewritten.
*/
if (PageUptodate(page) || PageLocked(page))
page_cache = generic_file_readahead(reada_ok, filp, inode, pos & PAGE_MASK, page, page_cache);
else if (reada_ok && filp->f_ramax > MIN_READAHEAD)
filp->f_ramax = MIN_READAHEAD;
wait_on_page(page);
if (!PageUptodate(page))
goto page_read_error;
success:
/*
* Ok, we have the page, it's up-to-date and ok,
* so now we can finally copy it to user space...
*/
{
unsigned long offset, nr;
offset = pos & ~PAGE_MASK;
nr = PAGE_SIZE - offset;
if (nr > count)
nr = count;
if (nr > inode->i_size - pos)
nr = inode->i_size - pos;
memcpy_tofs(buf, (void *) (page_address(page) + offset), nr);
release_page(page);
buf += nr;
pos += nr;
read += nr;
count -= nr;
if (count) {
/*
* to prevent hogging the CPU on well-cached systems,
* schedule if needed, it's safe to do it here:
*/
if (need_resched)
schedule();
continue;
}
break;
}
no_cached_page:
/*
* Ok, it wasn't cached, so we need to create a new
* page..
*/
if (!page_cache) {
page_cache = __get_free_page(GFP_KERNEL);
/*
* That could have slept, so go around to the
* very beginning..
*/
if (page_cache)
continue;
error = -ENOMEM;
break;
}
/*
* Ok, add the new page to the hash-queues...
*/
page = mem_map + MAP_NR(page_cache);
page_cache = 0;
add_to_page_cache(page, inode, pos & PAGE_MASK, hash);
/*
* Error handling is tricky. If we get a read error,
* the cached page stays in the cache (but uptodate=0),
* and the next process that accesses it will try to
* re-read it. This is needed for NFS etc, where the
* identity of the reader can decide if we can read the
* page or not..
*/
/*
* We have to read the page.
* If we were reading ahead, we had previously tried to read this page,
* That means that the page has probably been removed from the cache before
* the application process needs it, or has been rewritten.
* Decrease max readahead size to the minimum value in that situation.
*/
if (reada_ok && filp->f_ramax > MIN_READAHEAD)
filp->f_ramax = MIN_READAHEAD;
error = inode->i_op->readpage(inode, page);
if (!error)
goto found_page;
release_page(page);
break;
page_read_error:
/*
* We found the page, but it wasn't up-to-date.
* Try to re-read it _once_. We do this synchronously,
* because this happens only if there were errors.
*/
error = inode->i_op->readpage(inode, page);
if (!error) {
wait_on_page(page);
if (PageUptodate(page) && !PageError(page))
goto success;
error = -EIO; /* Some unspecified error occurred.. */
}
release_page(page);
break;
}
filp->f_pos = pos;
filp->f_reada = 1;
if (page_cache)
free_page(page_cache);
UPDATE_ATIME(inode)
if (!read)
read = error;
return read;
}
/*
* Semantics for shared and private memory areas are different past the end
* of the file. A shared mapping past the last page of the file is an error
* and results in a SIGBUS, while a private mapping just maps in a zero page.
*
* The goto's are kind of ugly, but this streamlines the normal case of having
* it in the page cache, and handles the special cases reasonably without
* having a lot of duplicated code.
*/
static unsigned long filemap_nopage(struct vm_area_struct * area, unsigned long address, int no_share)
{w momencie pojawienia się błędu braku strony wywoływana jest ta funkcja
filemap_nopage która jeśli jest to możliwe podaje adres strony wczytanej
do pamięci lub 0 jeśli nie mógł wczytać żadanej strony}
{
unsigned long offset;
struct page * page, **hash;
struct inode * inode = area->vm_inode;
unsigned long old_page, new_page;
new_page = 0;
/* offset w pliku szukanej strony */
offset = (address & PAGE_MASK) - area->vm_start + area->vm_offset;
if (offset >= inode->i_size && (area->vm_flags & VM_SHARED) && area->vm_mm == current->mm)
goto no_page; /*nie ma takiego adresu */
/*
* Do we have something in the page cache already?
*/
hash = page_hash(inode, offset);
page = __find_page(inode, offset, *hash);
if (!page)
goto no_cached_page;
found_page:
/*
* Ok, found a page in the page cache, now we need to check
* that it's up-to-date. First check whether we'll need an
* extra page -- better to overlap the allocation with the I/O.
*/
if (no_share && !new_page) {
new_page = __get_free_page(GFP_KERNEL);
if (!new_page)
goto failure;
}
if (PageLocked(page))
goto page_locked_wait;
if (!PageUptodate(page))
goto page_read_error;
success:
/*
* Found the page, need to check sharing and possibly
* copy it over to another page..
*/
old_page = page_address(page);
if (!no_share) {
/*
* Ok, we can share the cached page directly.. Get rid
* of any potential extra pages.
*/
if (new_page)
free_page(new_page);
flush_page_to_ram(old_page);
return old_page;
}
/*
* No sharing ... copy to the new page.
*/
memcpy((void *) new_page, (void *) old_page, PAGE_SIZE);
flush_page_to_ram(new_page);
release_page(page);
return new_page;
no_cached_page:
/*nie ma strony w cache'u */
/* przydzielamy wolną */
new_page = __get_free_page(GFP_KERNEL);
if (!new_page) /*nie udało się ? */
goto no_page;
/*
* During getting the above page we might have slept,
* so we need to re-check the situation with the page
* cache.. The page we just got may be useful if we
* can't share, so don't get rid of it here.
*/
page = find_page(inode, offset);
if (page) /* ostatnia szansa :-) */
goto found_page;
/*
* Now, create a new page-cache page from the page we got
*/
page = mem_map + MAP_NR(new_page);
new_page = 0;
add_to_page_cache(page, inode, offset, hash);
if (inode->i_op->readpage(inode, page) != 0)
goto failure;
/*
* Do a very limited read-ahead if appropriate
*/
if (PageLocked(page))
new_page = try_to_read_ahead(inode, offset + PAGE_SIZE, 0);
goto found_page;
page_locked_wait:/*strona zablokowana*/
__wait_on_page(page); /*czekamy na odblokowanie*/
if (PageUptodate(page))
goto success;
page_read_error:
/*
* Umm, take care of errors if the page isn't up-to-date.
* Try to re-read it _once_. We do this synchronously,
* because there really aren't any performance issues here
* and we need to check for errors.
*/
if (inode->i_op->readpage(inode, page) != 0)
goto failure;
wait_on_page(page);
if (PageError(page))
goto failure;
if (PageUptodate(page))
goto success;
/*
* Uhhuh.. Things didn't work out. Return zero to tell the
* mm layer so, possibly freeing the page cache page first.
*/
failure:
release_page(page);
if (new_page)
free_page(new_page);
no_page:
return 0;
}
/*
* Tries to write a shared mapped page to its backing store. May return -EIO
* if the disk is full.
*/
static inline int do_write_page(struct inode * inode, struct file * file,
const char * page, unsigned long offset)
/* Zapisywanie strony na dysk. Zwracane 0 jeśli OK
EIO jeśli blad */
{
int old_fs, retval;
unsigned long size;
size = offset + PAGE_SIZE;
/* refuse to extend file size.. */
if (S_ISREG(inode->i_mode)) {
if (size > inode->i_size)
size = inode->i_size;
/* Ho humm.. We should have tested for this earlier */
if (size < offset)
return -EIO;
}
old_fs = get_fs();
set_fs(KERNEL_DS);
retval = -EIO;
if (size == file->f_op->write(inode, file, (const char *) page, size))
retval = 0;
set_fs(old_fs);
return retval;
}
static int filemap_write_page(struct vm_area_struct * vma,
unsigned long offset,
unsigned long page)
/* zapisywanie strony będącej mapowaniem pliku
zwraca 0 jeśli operacja się powiodła
EOF jeśli wystapił błąd*/
{
int result;
struct file file;
struct inode * inode;
struct buffer_head * bh;
bh = mem_map[MAP_NR(page)].buffers;
if (bh) {/* w buforach zaznaczamy, że były jakieś zmiany */
/* whee.. just mark the buffer heads dirty */
struct buffer_head * tmp = bh;
do {
mark_buffer_dirty(tmp, 0);
tmp = tmp->b_this_page;
} while (tmp != bh);
return 0;
}
/* inicjalizujemy file */
inode = vma->vm_inode;
file.f_op = inode->i_op->default_file_ops;
if (!file.f_op->write)
return -EIO;
file.f_mode = 3;
file.f_flags = 0;
file.f_count = 1;
file.f_inode = inode;
file.f_pos = offset;
file.f_reada = 0;
down(&inode->i_sem); /* blokujemy semafor przy zapisie */
result = do_write_page(inode, &file, (const char *) page, offset);
up(&inode->i_sem); /* odblokowujemy semafor */
return result;
}
/*
* Swapping to a shared file: while we're busy writing out the page
* (and the page still exists in memory), we save the page information
* in the page table, so that "filemap_swapin()" can re-use the page
* immediately if it is called while we're busy swapping it out..
*
* Once we've written it all out, we mark the page entry "empty", which
* will result in a normal page-in (instead of a swap-in) from the now
* up-to-date disk file.
*/
int filemap_swapout(struct vm_area_struct * vma,
unsigned long offset,
pte_t *page_table)
/* wymiana strony dzielonej na dysk. Podczas zapisywania strona ta
jest dostępna gdyż zapisujemy informacje o niej w pte_t.
Filemap_swapin może więc bez wczytywania sięgnac do niej
jeśli jesteśmy zajeci zapisywaniem jej na dysk */
{
int error;
unsigned long page = pte_page(*page_table);
unsigned long entry = SWP_ENTRY(SHM_SWP_TYPE, MAP_NR(page));
flush_cache_page(vma, (offset + vma->vm_start - vma->vm_offset));
set_pte(page_table, __pte(entry));
flush_tlb_page(vma, (offset + vma->vm_start - vma->vm_offset));
error = filemap_write_page(vma, offset, page);
if (pte_val(*page_table) == entry)
pte_clear(page_table);
return error;
}
/*
* filemap_swapin() is called only if we have something in the page
* tables that is non-zero (but not present), which we know to be the
* page index of a page that is busy being swapped out (see above).
* So we just use it directly..
*/
static pte_t filemap_swapin(struct vm_area_struct * vma,
unsigned long offset,
unsigned long entry)
/* dostęp do strony dzielonej podczas gdy jest wykonywany filemap_swapin */
{
unsigned long page = SWP_OFFSET(entry);
mem_map[page].count++;
page = (page << PAGE_SHIFT) + PAGE_OFFSET;
return mk_pte(page,vma->vm_page_prot);
}
static inline int filemap_sync_pte(pte_t * ptep, struct vm_area_struct *vma,
unsigned long address, unsigned int flags)
/* w przypadku zmian na stronach które są dzielone zmienia ich kopie na dysku */
{
pte_t pte = *ptep;
unsigned long page;
int error;
if (pte_none(pte)) /* strona jest w pamięci lecz nie było jeszcze
do niej odwołań */
return 0;
if (!(flags & MS_INVALIDATE)) {
if (!pte_present(pte)) /* strony nie ma w pamięci */
return 0;
if (!pte_dirty(pte)) /* na stronie nie było żadnych zmian */
return 0;
/* nie robi nic */
flush_page_to_ram(pte_page(pte));
/* nie robi nic */
flush_cache_page(vma, address);
set_pte(ptep, pte_mkclean(pte)); /* *ptep=pte_mkclear(pte) */
flush_tlb_page(vma, address); /* procesor intel pamięta tablicę
stron procesu - funkcja ta mówi
mu, że coś uległo w niej
zmianie*/
page = pte_page(pte); /* adres strony */
mem_map[MAP_NR(page)].count++;
} else {
/* nic nie robi */
flush_cache_page(vma, address);
pte_clear(ptep);
flush_tlb_page(vma, address); /* funkcja opisana wyżej */
if (!pte_present(pte)) { /* strony nie ma w pamięci */
swap_free(pte_val(pte));
return 0;
}
page = pte_page(pte);
if (!pte_dirty(pte) || flags == MS_INVALIDATE) {
free_page(page);
return 0;
}
}
error = filemap_write_page(vma, address - vma->vm_start + vma->vm_offset, page);
free_page(page);
return error;
}
static inline int filemap_sync_pte_range(pmd_t * pmd,
unsigned long address, unsigned long size,
struct vm_area_struct *vma, unsigned long offset, unsigned int flags)
/* wywołuje filemap_sync_pte z kolejnymi stronami znajdujacymi sie
w obszarze (addresa, address+size) */
{
pte_t * pte;
unsigned long end;
int error;
if (pmd_none(*pmd)) /* podobnie jak w funkcji filemap_sync_pte */
return 0;
if (pmd_bad(*pmd)) {
printk("filemap_sync_pte_range: bad pmd (%08lx)\n", pmd_val(*pmd));
pmd_clear(pmd);
return 0;
}
pte = pte_offset(pmd, address);
offset += address & PMD_MASK;
address &= ~PMD_MASK;
end = address + size;
if (end > PMD_SIZE)
end = PMD_SIZE;
error = 0;
do {
error |= filemap_sync_pte(pte, vma, address + offset, flags);
address += PAGE_SIZE; /* przesuwanie się na kolejne strony */
pte++;
} while (address < end);
return error;
}
static inline int filemap_sync_pmd_range(pgd_t * pgd,
unsigned long address, unsigned long size,
struct vm_area_struct *vma, unsigned int flags)
/* wywołuje filemap_sync_pte_range dla każdego katalogu stron */
{
pmd_t * pmd;
unsigned long offset, end;
int error;
/* pgd_none() = 0 zawsze */
if (pgd_none(*pgd))
return 0;
/* pgd_bad() = 0 zawsze */
if (pgd_bad(*pgd)) {
printk("filemap_sync_pmd_range: bad pgd (%08lx)\n", pgd_val(*pgd));
pgd_clear(pgd);
return 0;
}
/* pmd - entry in a pgd */
pmd = pmd_offset(pgd, address);
offset = address & PGDIR_MASK;
address &= ~PGDIR_MASK;
end = address + size;
if (end > PGDIR_SIZE)
end = PGDIR_SIZE;
error = 0;
do {
error |= filemap_sync_pte_range(pmd, address, end - address, vma, offset, flags);
address = (address + PMD_SIZE) & PMD_MASK;
pmd++;
} while (address < end);
return error;
}
static int filemap_sync(struct vm_area_struct * vma, unsigned long address,
size_t size, unsigned int flags)
/* wywołuje filemap_sync_pmd_range dla każdego katalogu stron
Podwójne adresowanie*/
{
pgd_t * dir;
unsigned long end = address + size;
int error = 0;
dir = pgd_offset(vma->vm_mm, address);
/* nie robi nic */
flush_cache_range(vma->vm_mm, end - size, end);
while (address < end) {
error |= filemap_sync_pmd_range(dir, address, end - address, vma, flags);
/* nastepny adres */
address = (address + PGDIR_SIZE) & PGDIR_MASK;
dir++;
}
/* nic nie robi */
flush_tlb_range(vma->vm_mm, end - size, end);
return error;
}
/*
* This handles (potentially partial) area unmaps..
*/
static void filemap_unmap(struct vm_area_struct *vma, unsigned long start, size_t len)
{
filemap_sync(vma, start, len, MS_ASYNC);
}
/*
* Shared mappings need to be able to do the right thing at
* close/unmap/sync. They will also use the private file as
* backing-store for swapping..
*/
/* struktura dla pamięci dzielonej */
static struct vm_operations_struct file_shared_mmap = {
NULL, /* no special open */
NULL, /* no special close */
filemap_unmap, /* unmap - we need to sync the pages */
NULL, /* no special protect */
filemap_sync, /* sync */
NULL, /* advise */
filemap_nopage, /* nopage */
NULL, /* wppage */
filemap_swapout, /* swapout */
filemap_swapin, /* swapin */
};
/*
* Private mappings just need to be able to load in the map.
*
* (This is actually used for shared mappings as well, if we
* know they can't ever get write permissions..)
*/
/* struktura dla pemieci niedzielonej */
static struct vm_operations_struct file_private_mmap = {
NULL, /* open */
NULL, /* close */
NULL, /* unmap */
NULL, /* protect */
NULL, /* sync */
NULL, /* advise */
filemap_nopage, /* nopage */
NULL, /* wppage */
NULL, /* swapout */
NULL, /* swapin */
};
/* This is used for a general mmap of a disk file */
int generic_file_mmap(struct inode * inode, struct file * file, struct vm_area_struct * vma)
/* argumenty
inode - i-węzeł mapowanego pliku
file - "określenie" pliku
vma - obszar wirtualnej przestrzeni adresowej
*/
{
struct vm_operations_struct * ops; /* wirtualne funkcje */
if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) {
ops = &file_shared_mmap;
/*file_shared_mmap zawiera ustawienia vm_operations_struct
dla obszaru dzielonego. */
/* share_page() can only guarantee proper page sharing if
* the offsets are all page aligned. */
if (vma->vm_offset & (PAGE_SIZE - 1))
return -EINVAL;
} else {
ops = &file_private_mmap;
/* file_private_mmap zawiera ustawienia vm_operations_struct
dla obszaru niedzielonego */
if (vma->vm_offset & (inode->i_sb->s_blocksize - 1))
return -EINVAL;
}
if (!inode->i_sb || !S_ISREG(inode->i_mode))
return -EACCES;
if (!inode->i_op || !inode->i_op->readpage)
return -ENOEXEC;
UPDATE_ATIME(inode)
vma->vm_inode = inode; /* ustawienie wezła dla vma */
inode->i_count++; /* i_count - licznik odwołań do wezła */
vma->vm_ops = ops; /* urządzenie mapujące */
return 0;
}
/*
* The msync() system call.
*/
static int msync_interval(struct vm_area_struct * vma,
unsigned long start, unsigned long end, int flags)
{
if (!vma->vm_inode)
return 0;
if (vma->vm_ops->sync) {
int error;
error = vma->vm_ops->sync(vma, start, end-start, flags);
if (error)
return error;
if (flags & MS_SYNC)
return file_fsync(vma->vm_inode, NULL);
return 0;
}
return 0;
}
asmlinkage int sys_msync(unsigned long start, size_t len, int flags)
{
unsigned long end;
struct vm_area_struct * vma;
int unmapped_error, error;
if (start & ~PAGE_MASK)
return -EINVAL;
len = (len + ~PAGE_MASK) & PAGE_MASK;
end = start + len;
if (end < start)
return -EINVAL;
if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
return -EINVAL;
if (end == start)
return 0;
/*
* If the interval [start,end) covers some unmapped address ranges,
* just ignore them, but return -EFAULT at the end.
*/
vma = find_vma(current->mm, start);
unmapped_error = 0;
for (;;) {
/* Still start < end. */
if (!vma)
return -EFAULT;
/* Here start < vma->vm_end. */
if (start < vma->vm_start) {
unmapped_error = -EFAULT;
start = vma->vm_start;
}
/* Here vma->vm_start <= start < vma->vm_end. */
if (end <= vma->vm_end) {
if (start < end) {
error = msync_interval(vma, start, end, flags);
if (error)
return error;
}
return unmapped_error;
}
/* Here vma->vm_start <= start < vma->vm_end < end. */
error = msync_interval(vma, start, vma->vm_end, flags);
if (error)
return error;
start = vma->vm_end;
vma = vma->vm_next;
}
}
Radoslaw Szymaszek