Commit d3602444 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

shmem_getpage return page locked 



In the new aops, write_begin is supposed to return the page locked: though
I've seen no ill effects, that's been overlooked in the case of
shmem_write_begin, and should be fixed.  Then shmem_write_end must unlock the
page: do so _after_ updating i_size, as we found to be important in other
filesystems (though since shmem pages don't go the usual writeback route, they
never suffered from that corruption).

For shmem_write_begin to return the page locked, we need shmem_getpage to
return the page locked in SGP_WRITE case as well as SGP_CACHE case: let's
simplify the interface and return it locked even when SGP_READ.

Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 27d54b39

mm/shmem.c

+13 −9
Original line number Original line Diff line number Diff line
@@ -729,6 +729,8 @@ static int shmem_notify_change(struct dentry *dentry, struct iattr *attr) 
				(void) shmem_getpage(inode,

				(void) shmem_getpage(inode,

					attr->ia_size>>PAGE_CACHE_SHIFT,

					attr->ia_size>>PAGE_CACHE_SHIFT,

						&page, SGP_READ, NULL);

						&page, SGP_READ, NULL);

				if (page)

					unlock_page(page);

			}

			}

			/*

			/*

			 * Reset SHMEM_PAGEIN flag so that shmem_truncate can

			 * Reset SHMEM_PAGEIN flag so that shmem_truncate can
@@ -1286,12 +1288,7 @@ repeat: 
		SetPageUptodate(filepage);

		SetPageUptodate(filepage);

	}

	}

done:

done:

	if (*pagep != filepage) {

	*pagep = filepage;

	*pagep = filepage;

		if (sgp != SGP_CACHE)

			unlock_page(filepage);



	}

	return 0;

	return 0;





failed:

failed:
@@ -1469,12 +1466,13 @@ shmem_write_end(struct file *file, struct address_space *mapping, 
{

{

	struct inode *inode = mapping->host;

	struct inode *inode = mapping->host;





	set_page_dirty(page);

	page_cache_release(page);



	if (pos + copied > inode->i_size)

	if (pos + copied > inode->i_size)

		i_size_write(inode, pos + copied);

		i_size_write(inode, pos + copied);





	unlock_page(page);

	set_page_dirty(page);

	page_cache_release(page);



	return copied;

	return copied;

}

}
@@ -1529,6 +1527,7 @@ shmem_file_write(struct file *file, const char __user *buf, size_t count, loff_t 
		if (err)

		if (err)

			break;

			break;





		unlock_page(page);

		left = bytes;

		left = bytes;

		if (PageHighMem(page)) {

		if (PageHighMem(page)) {

			volatile unsigned char dummy;

			volatile unsigned char dummy;
@@ -1610,6 +1609,8 @@ static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_ 
				desc->error = 0;

				desc->error = 0;

			break;

			break;

		}

		}

		if (page)

			unlock_page(page);





		/*

		/*

		 * We must evaluate after, since reads (unlike writes)

		 * We must evaluate after, since reads (unlike writes)
@@ -1899,6 +1900,7 @@ static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *s 
			iput(inode);

			iput(inode);

			return error;

			return error;

		}

		}

		unlock_page(page);

		inode->i_op = &shmem_symlink_inode_operations;

		inode->i_op = &shmem_symlink_inode_operations;

		kaddr = kmap_atomic(page, KM_USER0);

		kaddr = kmap_atomic(page, KM_USER0);

		memcpy(kaddr, symname, len);

		memcpy(kaddr, symname, len);
@@ -1926,6 +1928,8 @@ static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd) 
	struct page *page = NULL;

	struct page *page = NULL;

	int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);

	int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);

	nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));

	nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));

	if (page)

		unlock_page(page);

	return page;

	return page;

}

}

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