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Fix prepare and commit_write to do the right thing

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Even when we're doing syncronous writeback, as we currently do
for write() operations, it's important to correctly fill, and flag
the pages we're writing to. Not doing so has a huge performance
penalty, as it means even when we've just written a page, we have to
pull it back from the backing store for a read.

This code fixes prepare_write and commit_write (for RHEL5) and
write_begin and write_end (for Fedora) to correctly populate and
flag pages which are being written.

Change-Id: Iaa2165b9b429000dcf0c6dd452e3eb8033257277
Reviewed-on: http://gerrit.openafs.org/820
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
This commit is contained in:
Simon Wilkinson 2009-10-26 19:58:53 +00:00 committed by Derrick Brashear
parent 4f91de7cf4
commit dce56fb8ce
1 changed files with 52 additions and 8 deletions
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60
src/afs/LINUX/osi_vnodeops.c
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@ -2227,15 +2227,23 @@ afs_linux_permission(struct inode *ip, int mode)
return afs_convert_code(code);
}
#if !defined(HAVE_WRITE_BEGIN)
static int
afs_linux_commit_write(struct file *file, struct page *page, unsigned offset,
unsigned to)
{
int code;
struct inode *inode = FILE_INODE(file);
loff_t pagebase = page_offset(page);
code = afs_linux_writepage_sync(file->f_dentry->d_inode, page,
offset, to - offset);
if (i_size_read(inode) < (pagebase + offset))
i_size_write(inode, pagebase + offset);
if (PageChecked(page)) {
SetPageUptodate(page);
ClearPageChecked(page);
}
code = afs_linux_writepage_sync(inode, page, offset, to - offset);
return code;
}
@ -2244,20 +2252,47 @@ static int
afs_linux_prepare_write(struct file *file, struct page *page, unsigned from,
unsigned to)
{
/* http://kerneltrap.org/node/4941 details the expected behaviour of
* prepare_write. Essentially, if the page exists within the file,
* and is not being fully written, then we should populate it.
*/
if (!PageUptodate(page)) {
loff_t pagebase = page_offset(page);
loff_t isize = i_size_read(page->mapping->host);
/* Is the location we are writing to beyond the end of the file? */
if (pagebase >= isize ||
((from == 0) && (pagebase + to) >= isize)) {
zero_user_segments(page, 0, from, to, PAGE_CACHE_SIZE);
SetPageChecked(page);
/* Are we we writing a full page */
} else if (from == 0 && to == PAGE_CACHE_SIZE) {
SetPageChecked(page);
/* Is the page readable, if it's wronly, we don't care, because we're
* not actually going to read from it ... */
} else if ((file->f_flags && O_ACCMODE) != O_WRONLY) {
/* We don't care if fillpage fails, because if it does the page
* won't be marked as up to date
*/
afs_linux_fillpage(file, page);
}
}
return 0;
}
#else
#if defined(HAVE_WRITE_BEGIN)
static int
afs_linux_write_end(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned copied,
struct page *page, void *fsdata)
{
int code;
unsigned from = pos & (PAGE_CACHE_SIZE - 1);
unsigned int from = pos & (PAGE_CACHE_SIZE - 1);
code = afs_linux_commit_write(file, page, from, from + len);
code = afs_linux_writepage_sync(file->f_dentry->d_inode, page,
from, copied);
unlock_page(page);
page_cache_release(page);
return code;
@ -2270,10 +2305,19 @@ afs_linux_write_begin(struct file *file, struct address_space *mapping,
{
struct page *page;
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
unsigned int from = pos & (PAGE_CACHE_SIZE - 1);
int code;
page = grab_cache_page_write_begin(mapping, index, flags);
*pagep = page;
return 0;
code = afs_linux_prepare_write(file, page, from, from + len);
if (code) {
unlock_page(page);
page_cache_release(page);
}
return code;
}
#endif