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ocfs2: Fix ocfs2_page_mkwrite()

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This patch address two shortcomings in ocfs2_page_mkwrite():
1. Makes the function return better VM_FAULT_* errors.
2. It handles a error that is triggered when a page is dropped from the mapping
due to memory pressure. This patch locks the page to prevent that.

[Patch was cleaned up by Sunil Mushran.]

Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
This commit is contained in:
Wengang Wang
2011-07-24 10:36:54 -07:00
committed by Sunil Mushran
parent a035bff6b8
commit 5cffff9e29
2 changed files with 67 additions and 37 deletions
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51
fs/ocfs2/aops.c
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@@ -862,6 +862,12 @@ struct ocfs2_write_ctxt {
struct page *w_pages[OCFS2_MAX_CTXT_PAGES];
struct page *w_target_page;
/*
* w_target_locked is used for page_mkwrite path indicating no unlocking
* against w_target_page in ocfs2_write_end_nolock.
*/
unsigned int w_target_locked:1;
/*
* ocfs2_write_end() uses this to know what the real range to
* write in the target should be.
@@ -895,6 +901,24 @@ void ocfs2_unlock_and_free_pages(struct page **pages, int num_pages)
static void ocfs2_free_write_ctxt(struct ocfs2_write_ctxt *wc)
{
int i;
/*
* w_target_locked is only set to true in the page_mkwrite() case.
* The intent is to allow us to lock the target page from write_begin()
* to write_end(). The caller must hold a ref on w_target_page.
*/
if (wc->w_target_locked) {
BUG_ON(!wc->w_target_page);
for (i = 0; i < wc->w_num_pages; i++) {
if (wc->w_target_page == wc->w_pages[i]) {
wc->w_pages[i] = NULL;
break;
}
}
mark_page_accessed(wc->w_target_page);
page_cache_release(wc->w_target_page);
}
ocfs2_unlock_and_free_pages(wc->w_pages, wc->w_num_pages);
brelse(wc->w_di_bh);
@@ -1132,20 +1156,17 @@ static int ocfs2_grab_pages_for_write(struct address_space *mapping,
*/
lock_page(mmap_page);
/* Exit and let the caller retry */
if (mmap_page->mapping != mapping) {
WARN_ON(mmap_page->mapping);
unlock_page(mmap_page);
/*
* Sanity check - the locking in
* ocfs2_pagemkwrite() should ensure
* that this code doesn't trigger.
*/
ret = -EINVAL;
mlog_errno(ret);
ret = -EAGAIN;
goto out;
}
page_cache_get(mmap_page);
wc->w_pages[i] = mmap_page;
wc->w_target_locked = true;
} else {
wc->w_pages[i] = find_or_create_page(mapping, index,
GFP_NOFS);
@@ -1160,6 +1181,8 @@ static int ocfs2_grab_pages_for_write(struct address_space *mapping,
wc->w_target_page = wc->w_pages[i];
}
out:
if (ret)
wc->w_target_locked = false;
return ret;
}
@@ -1817,11 +1840,23 @@ try_again:
*/
ret = ocfs2_grab_pages_for_write(mapping, wc, wc->w_cpos, pos, len,
cluster_of_pages, mmap_page);
if (ret) {
if (ret && ret != -EAGAIN) {
mlog_errno(ret);
goto out_quota;
}
/*
* ocfs2_grab_pages_for_write() returns -EAGAIN if it could not lock
* the target page. In this case, we exit with no error and no target
* page. This will trigger the caller, page_mkwrite(), to re-try
* the operation.
*/
if (ret == -EAGAIN) {
BUG_ON(wc->w_target_page);
ret = 0;
goto out_quota;
}
ret = ocfs2_write_cluster_by_desc(mapping, data_ac, meta_ac, wc, pos,
len);
if (ret) {