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Commit 8a236264 authored by Steve French's avatar Steve French
Browse files

[CIFS] cifs_prepare_write was incorrectly rereading page in some cases 



Noticed by Shaggy.

Signed-off-by: default avatarShaggy <shaggy@us.ibm.com>
Signed-off-by: default avatarSteve French <sfrench@us.ibm.com>
parent c7af1857

fs/cifs/CHANGES

+3 −2
Original line number Diff line number Diff line
@@ -2,7 +2,8 @@ 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

------------

fs/cifs/file.c

+40 −22
Original line number Diff line number Diff line
@@ -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;

	loff_t i_size;

	loff_t offset;



	cFYI(1, ("prepare write for page %p from %d to %d",page,from,to));

	if (!PageUptodate(page)) {

	/*	if (to - from != PAGE_CACHE_SIZE) {

	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;

	}



	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);

		} */

		/* 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);



	} else if ((file->f_flags & O_ACCMODE) != O_WRONLY) {

		/* 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 */

		}

		/* 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 */

	}



	/* BB should we pass any errors back? 

	   e.g. if we do not have read access to the file */

	/* 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;

}

fs/cifs/transport.c

+2 −4
Original line number Diff line number Diff line
@@ -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);