Commit 85bfa7dc authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds

[PATCH] grab_cache_page_nowait deadlock fix

- If grab_cache_page_nowait() is to be called while holding a lock on
  a different page, it must perform memory allocations with GFP_NOFS.
  Otherwise it could come back onto the locked page (if it's dirty) and
  deadlock.

  Also tidy this function up a bit - the checks in there were overly
  paranoid.

- In a few of places, look to see if we can avoid a buslocked cycle
  and dirtying of a cacheline.
parent 386b1f74
...@@ -445,7 +445,9 @@ int fail_writepage(struct page *page) ...@@ -445,7 +445,9 @@ int fail_writepage(struct page *page)
{ {
/* Only activate on memory-pressure, not fsync.. */ /* Only activate on memory-pressure, not fsync.. */
if (current->flags & PF_MEMALLOC) { if (current->flags & PF_MEMALLOC) {
if (!PageActive(page))
activate_page(page); activate_page(page);
if (!PageReferenced(page))
SetPageReferenced(page); SetPageReferenced(page);
} }
...@@ -868,55 +870,35 @@ struct page *grab_cache_page(struct address_space *mapping, unsigned long index) ...@@ -868,55 +870,35 @@ struct page *grab_cache_page(struct address_space *mapping, unsigned long index)
* This is intended for speculative data generators, where the data can * This is intended for speculative data generators, where the data can
* be regenerated if the page couldn't be grabbed. This routine should * be regenerated if the page couldn't be grabbed. This routine should
* be safe to call while holding the lock for another page. * be safe to call while holding the lock for another page.
*
* Clear __GFP_FS when allocating the page to avoid recursion into the fs
* and deadlock against the caller's locked page.
*/ */
struct page *grab_cache_page_nowait(struct address_space *mapping, unsigned long index) struct page *
grab_cache_page_nowait(struct address_space *mapping, unsigned long index)
{ {
struct page *page; struct page *page = find_get_page(mapping, index);
page = find_get_page(mapping, index);
if ( page ) { if (page) {
if ( !TestSetPageLocked(page) ) { if (!TestSetPageLocked(page))
/* Page found and locked */
/* This test is overly paranoid, but what the heck... */
if ( unlikely(page->mapping != mapping || page->index != index) ) {
/* Someone reallocated this page under us. */
unlock_page(page);
page_cache_release(page);
return NULL;
} else {
return page; return page;
}
} else {
/* Page locked by someone else */
page_cache_release(page); page_cache_release(page);
return NULL; return NULL;
} }
} page = alloc_pages(mapping->gfp_mask & ~__GFP_FS, 0);
if (page && add_to_page_cache_unique(page, mapping, index)) {
page = page_cache_alloc(mapping);
if (unlikely(!page))
return NULL; /* Failed to allocate a page */
if (unlikely(add_to_page_cache_unique(page, mapping, index))) {
/*
* Someone else grabbed the page already, or
* failed to allocate a radix-tree node
*/
page_cache_release(page); page_cache_release(page);
return NULL; page = NULL;
} }
return page; return page;
} }
/* /*
* Mark a page as having seen activity. * Mark a page as having seen activity.
* *
* If it was already so marked, move it * inactive,unreferenced -> inactive,referenced
* to the active queue and drop the referenced * inactive,referenced -> active,unreferenced
* bit. Otherwise, just mark it for future * active,unreferenced -> active,referenced
* action..
*/ */
void mark_page_accessed(struct page *page) void mark_page_accessed(struct page *page)
{ {
...@@ -924,10 +906,9 @@ void mark_page_accessed(struct page *page) ...@@ -924,10 +906,9 @@ void mark_page_accessed(struct page *page)
activate_page(page); activate_page(page);
ClearPageReferenced(page); ClearPageReferenced(page);
return; return;
} } else if (!PageReferenced(page)) {
/* Mark the page referenced, AFTER checking for previous usage.. */
SetPageReferenced(page); SetPageReferenced(page);
}
} }
/* /*
...@@ -2286,6 +2267,7 @@ generic_file_write(struct file *file, const char *buf, ...@@ -2286,6 +2267,7 @@ generic_file_write(struct file *file, const char *buf,
} }
} }
kunmap(page); kunmap(page);
if (!PageReferenced(page))
SetPageReferenced(page); SetPageReferenced(page);
unlock_page(page); unlock_page(page);
page_cache_release(page); page_cache_release(page);
......
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