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[CIFS] cifs_prepare_write was incorrectly rereading page in some cases

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Noticed by Shaggy.

Signed-off-by: Shaggy <shaggy@us.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
This commit is contained in:
Steve French
2007-03-06 00:31:00 +00:00
parent c7af1857ef
commit 8a236264f7
3 changed files with 48 additions and 31 deletions
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68
fs/cifs/file.c
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@@ -1992,34 +1992,52 @@ static int cifs_prepare_write(struct file *file, struct page *page,
unsigned from, unsigned to)
{
int rc = 0;
loff_t offset = (loff_t)page->index << PAGE_CACHE_SHIFT;
cFYI(1, ("prepare write for page %p from %d to %d",page,from,to));
if (!PageUptodate(page)) {
/* if (to - from != PAGE_CACHE_SIZE) {
void *kaddr = kmap_atomic(page, KM_USER0);
memset(kaddr, 0, from);
memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
flush_dcache_page(page);
kunmap_atomic(kaddr, KM_USER0);
} */
/* If we are writing a full page it will be up to date,
no need to read from the server */
if ((to == PAGE_CACHE_SIZE) && (from == 0))
SetPageUptodate(page);
loff_t i_size;
loff_t offset;
/* might as well read a page, it is fast enough */
if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
rc = cifs_readpage_worker(file, page, &offset);
} else {
/* should we try using another file handle if there is one -
how would we lock it to prevent close of that handle
racing with this read?
In any case this will be written out by commit_write */
}
cFYI(1, ("prepare write for page %p from %d to %d",page,from,to));
if (PageUptodate(page))
return 0;
/* If we are writing a full page it will be up to date,
no need to read from the server */
if ((to == PAGE_CACHE_SIZE) && (from == 0)) {
SetPageUptodate(page);
return 0;
}
/* BB should we pass any errors back?
e.g. if we do not have read access to the file */
offset = (loff_t)page->index << PAGE_CACHE_SHIFT;
i_size = i_size_read(page->mapping->host);
if ((offset >= i_size) ||
((from == 0) && (offset + to) >= i_size)) {
/*
* We don't need to read data beyond the end of the file.
* zero it, and set the page uptodate
*/
void *kaddr = kmap_atomic(page, KM_USER0);
if (from)
memset(kaddr, 0, from);
if (to < PAGE_CACHE_SIZE)
memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
flush_dcache_page(page);
kunmap_atomic(kaddr, KM_USER0);
SetPageUptodate(page);
} else if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
/* might as well read a page, it is fast enough */
rc = cifs_readpage_worker(file, page, &offset);
} else {
/* we could try using another file handle if there is one -
but how would we lock it to prevent close of that handle
racing with this read? In any case
this will be written out by commit_write so is fine */
}
/* we do not need to pass errors back
e.g. if we do not have read access to the file
because cifs_commit_write will do the right thing. -- shaggy */
return 0;
}