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ecryptfs: remove unnecessary decrypt when extending a file

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Removes an unecessary page decrypt from ecryptfs_begin_write when the
page is beyond the current file size. Previously, the call to
ecryptfs_decrypt_page would result in a read of 0 bytes, but still
attempt to decrypt an entire page. This patch detects that case and
merely zeros the page before marking it up-to-date.

Signed-off-by: Frank Swiderski <fes@chromium.org>
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
This commit is contained in:
Frank Swiderski 2010-11-15 10:43:22 -08:00 • committed by Tyler Hicks
parent f24b38874e
commit 24562486be
1 changed files with 14 additions and 8 deletions
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12
fs/ecryptfs/mmap.c
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@ -290,6 +290,7 @@ static int ecryptfs_write_begin(struct file *file,
return -ENOMEM; return -ENOMEM;
*pagep = page; *pagep = page;
prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
if (!PageUptodate(page)) { if (!PageUptodate(page)) {
struct ecryptfs_crypt_stat *crypt_stat = struct ecryptfs_crypt_stat *crypt_stat =
&ecryptfs_inode_to_private(mapping->host)->crypt_stat; &ecryptfs_inode_to_private(mapping->host)->crypt_stat;
@ -334,19 +335,24 @@ static int ecryptfs_write_begin(struct file *file,
} }
SetPageUptodate(page); SetPageUptodate(page);
} }
} else {
if (prev_page_end_size
>= i_size_read(page->mapping->host)) {
zero_user(page, 0, PAGE_CACHE_SIZE);
} else { } else {
rc = ecryptfs_decrypt_page(page); rc = ecryptfs_decrypt_page(page);
if (rc) { if (rc) {
printk(KERN_ERR "%s: Error decrypting page " printk(KERN_ERR "%s: Error decrypting "
"at index [%ld]; rc = [%d]\n", "page at index [%ld]; "
"rc = [%d]\n",
__func__, page->index, rc); __func__, page->index, rc);
ClearPageUptodate(page); ClearPageUptodate(page);
goto out; goto out;
} }
}
SetPageUptodate(page); SetPageUptodate(page);
} }
} }
prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
/* If creating a page or more of holes, zero them out via truncate. /* If creating a page or more of holes, zero them out via truncate.
* Note, this will increase i_size. */ * Note, this will increase i_size. */
if (index != 0) { if (index != 0) {