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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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5
fs/cifs/CHANGES
View File

@ -2,8 +2,9 @@ Verison 1.48
------------
Fix mtime bouncing around from local idea of last write times to remote time.
Fix hang (in i_size_read) when simultaneous size update of same remote file
on smp system corrupts sequence number.
on smp system corrupts sequence number. Do not reread unnecessarily partial page
(which we are about to overwrite anyway) when writing out file opened rw.
Version 1.47
------------
Fix oops in list_del during mount caused by unaligned string.

68
fs/cifs/file.c
View File

@ -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;
}

6
fs/cifs/transport.c
View File

@ -499,7 +499,7 @@ SendReceive2(const unsigned int xid, struct cifsSesInfo *ses,
due to last connection to this server being unmounted */
if (signal_pending(current)) {
/* if signal pending do not hold up user for full smb timeout
but we still give response a change to complete */
but we still give response a chance to complete */
timeout = 2 * HZ;
}
@ -587,7 +587,6 @@ SendReceive2(const unsigned int xid, struct cifsSesInfo *ses,
}
out:
DeleteMidQEntry(midQ);
atomic_dec(&ses->server->inFlight);
wake_up(&ses->server->request_q);
@ -681,7 +680,7 @@ SendReceive(const unsigned int xid, struct cifsSesInfo *ses,
due to last connection to this server being unmounted */
if (signal_pending(current)) {
/* if signal pending do not hold up user for full smb timeout
but we still give response a change to complete */
but we still give response a chance to complete */
timeout = 2 * HZ;
}
@ -765,7 +764,6 @@ SendReceive(const unsigned int xid, struct cifsSesInfo *ses,
}
out:
DeleteMidQEntry(midQ);
atomic_dec(&ses->server->inFlight);
wake_up(&ses->server->request_q);