[CIFS] cifs_prepare_write was incorrectly rereading page in some cases
Noticed by Shaggy.
Signed-off-by: Shaggy <shaggy@us.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index c07ff83..2d3275b 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1992,34 +1992,52 @@
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;
}