![Andrew Morton](/assets/img/avatar_default.png)
Add two new linux-specific fadvise extensions(): LINUX_FADV_ASYNC_WRITE: start async writeout of any dirty pages between file offsets `offset' and `offset+len'. Any pages which are currently under writeout are skipped, whether or not they are dirty. LINUX_FADV_WRITE_WAIT: wait upon writeout of any dirty pages between file offsets `offset' and `offset+len'. By combining these two operations the application may do several things: LINUX_FADV_ASYNC_WRITE: push some or all of the dirty pages at the disk. LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE: push all of the currently dirty pages at the disk. LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE, LINUX_FADV_WRITE_WAIT: push all of the currently dirty pages at the disk, wait until they have been written. It should be noted that none of these operations write out the file's metadata. So unless the application is strictly performing overwrites of already-instantiated disk blocks, there are no guarantees here that the data will be available after a crash. To complete this suite of operations I guess we should have a "sync file metadata only" operation. This gives applications access to all the building blocks needed for all sorts of sync operations. But sync-metadata doesn't fit well with the fadvise() interface. Probably it should be a new syscall: sys_fmetadatasync(). The patch also diddles with the meaning of `endbyte' in sys_fadvise64_64(). It is made to represent that last affected byte in the file (ie: it is inclusive). Generally, all these byterange and pagerange functions are inclusive so we can easily represent EOF with -1. As Ulrich notes, these two functions are somewhat abusive of the fadvise() concept, which appears to be "set the future policy for this fd". But these commands are a perfect fit with the fadvise() impementation, and several of the existing fadvise() commands are synchronous and don't affect future policy either. I think we can live with the slight incongruity. Cc: Michael Kerrisk <mtk-manpages@gmx.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
157 lines
3.9 KiB
C
157 lines
3.9 KiB
C
/*
|
|
* mm/fadvise.c
|
|
*
|
|
* Copyright (C) 2002, Linus Torvalds
|
|
*
|
|
* 11Jan2003 akpm@digeo.com
|
|
* Initial version.
|
|
*/
|
|
|
|
#include <linux/kernel.h>
|
|
#include <linux/file.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/pagemap.h>
|
|
#include <linux/backing-dev.h>
|
|
#include <linux/pagevec.h>
|
|
#include <linux/fadvise.h>
|
|
#include <linux/writeback.h>
|
|
#include <linux/syscalls.h>
|
|
|
|
#include <asm/unistd.h>
|
|
|
|
/*
|
|
* POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
|
|
* deactivate the pages and clear PG_Referenced.
|
|
*
|
|
* LINUX_FADV_ASYNC_WRITE: start async writeout of any dirty pages between file
|
|
* offsets `offset' and `offset+len' inclusive. Any pages which are currently
|
|
* under writeout are skipped, whether or not they are dirty.
|
|
*
|
|
* LINUX_FADV_WRITE_WAIT: wait upon writeout of any dirty pages between file
|
|
* offsets `offset' and `offset+len'.
|
|
*
|
|
* By combining these two operations the application may do several things:
|
|
*
|
|
* LINUX_FADV_ASYNC_WRITE: push some or all of the dirty pages at the disk.
|
|
*
|
|
* LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE: push all of the currently
|
|
* dirty pages at the disk.
|
|
*
|
|
* LINUX_FADV_WRITE_WAIT, LINUX_FADV_ASYNC_WRITE, LINUX_FADV_WRITE_WAIT: push
|
|
* all of the currently dirty pages at the disk, wait until they have been
|
|
* written.
|
|
*
|
|
* It should be noted that none of these operations write out the file's
|
|
* metadata. So unless the application is strictly performing overwrites of
|
|
* already-instantiated disk blocks, there are no guarantees here that the data
|
|
* will be available after a crash.
|
|
*/
|
|
asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
|
|
{
|
|
struct file *file = fget(fd);
|
|
struct address_space *mapping;
|
|
struct backing_dev_info *bdi;
|
|
loff_t endbyte; /* inclusive */
|
|
pgoff_t start_index;
|
|
pgoff_t end_index;
|
|
unsigned long nrpages;
|
|
int ret = 0;
|
|
|
|
if (!file)
|
|
return -EBADF;
|
|
|
|
if (S_ISFIFO(file->f_dentry->d_inode->i_mode)) {
|
|
ret = -ESPIPE;
|
|
goto out;
|
|
}
|
|
|
|
mapping = file->f_mapping;
|
|
if (!mapping || len < 0) {
|
|
ret = -EINVAL;
|
|
goto out;
|
|
}
|
|
|
|
if (mapping->a_ops->get_xip_page)
|
|
/* no bad return value, but ignore advice */
|
|
goto out;
|
|
|
|
/* Careful about overflows. Len == 0 means "as much as possible" */
|
|
endbyte = offset + len;
|
|
if (!len || endbyte < len)
|
|
endbyte = -1;
|
|
else
|
|
endbyte--; /* inclusive */
|
|
|
|
bdi = mapping->backing_dev_info;
|
|
|
|
switch (advice) {
|
|
case POSIX_FADV_NORMAL:
|
|
file->f_ra.ra_pages = bdi->ra_pages;
|
|
break;
|
|
case POSIX_FADV_RANDOM:
|
|
file->f_ra.ra_pages = 0;
|
|
break;
|
|
case POSIX_FADV_SEQUENTIAL:
|
|
file->f_ra.ra_pages = bdi->ra_pages * 2;
|
|
break;
|
|
case POSIX_FADV_WILLNEED:
|
|
case POSIX_FADV_NOREUSE:
|
|
if (!mapping->a_ops->readpage) {
|
|
ret = -EINVAL;
|
|
break;
|
|
}
|
|
|
|
/* First and last PARTIAL page! */
|
|
start_index = offset >> PAGE_CACHE_SHIFT;
|
|
end_index = endbyte >> PAGE_CACHE_SHIFT;
|
|
|
|
/* Careful about overflow on the "+1" */
|
|
nrpages = end_index - start_index + 1;
|
|
if (!nrpages)
|
|
nrpages = ~0UL;
|
|
|
|
ret = force_page_cache_readahead(mapping, file,
|
|
start_index,
|
|
max_sane_readahead(nrpages));
|
|
if (ret > 0)
|
|
ret = 0;
|
|
break;
|
|
case POSIX_FADV_DONTNEED:
|
|
if (!bdi_write_congested(mapping->backing_dev_info))
|
|
filemap_flush(mapping);
|
|
|
|
/* First and last FULL page! */
|
|
start_index = (offset+(PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
|
|
end_index = (endbyte >> PAGE_CACHE_SHIFT);
|
|
|
|
if (end_index >= start_index)
|
|
invalidate_mapping_pages(mapping, start_index,
|
|
end_index);
|
|
break;
|
|
case LINUX_FADV_ASYNC_WRITE:
|
|
ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
|
|
WB_SYNC_NONE);
|
|
break;
|
|
case LINUX_FADV_WRITE_WAIT:
|
|
ret = wait_on_page_writeback_range(mapping,
|
|
offset >> PAGE_CACHE_SHIFT,
|
|
endbyte >> PAGE_CACHE_SHIFT);
|
|
break;
|
|
default:
|
|
ret = -EINVAL;
|
|
}
|
|
out:
|
|
fput(file);
|
|
return ret;
|
|
}
|
|
|
|
#ifdef __ARCH_WANT_SYS_FADVISE64
|
|
|
|
asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
|
|
{
|
|
return sys_fadvise64_64(fd, offset, len, advice);
|
|
}
|
|
|
|
#endif
|