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Merge "filemap-drop-the-mmap_sem-for-all-blocking-operations-fix"

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qctecmdr Service 2019-03-17 09:15:12 -07:00 committed by Gerrit - the friendly Code Review server
commit 637e9cd0d1
1 changed files with 31 additions and 14 deletions
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45
mm/filemap.c
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@ -2275,6 +2275,12 @@ static struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf,
int flags = vmf->flags;
if (fpin)
return fpin;
/*
* FAULT_FLAG_RETRY_NOWAIT means we don't want to wait on page locks or
* anything, so we only pin the file and drop the mmap_sem if only
* FAULT_FLAG_ALLOW_RETRY is set.
*/
if ((flags & (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT)) ==
FAULT_FLAG_ALLOW_RETRY) {
fpin = get_file(vmf->vma->vm_file);
@ -2284,10 +2290,15 @@ static struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf,
}
/*
* Works similar to lock_page_or_retry, except it will pin the file and drop the
* mmap_sem if necessary and then lock the page, and return 1 in this case.
* This means the caller needs to deal with the fpin appropriately. 0 return is
* the same as in lock_page_or_retry.
* lock_page_maybe_drop_mmap - lock the page, possibly dropping the mmap_sem
* @vmf - the vm_fault for this fault.
* @page - the page to lock.
* @fpin - the pointer to the file we may pin (or is already pinned).
*
* This works similar to lock_page_or_retry in that it can drop the mmap_sem.
* It differs in that it actually returns the page locked if it returns 1 and 0
* if it couldn't lock the page. If we did have to drop the mmap_sem then fpin
* will point to the pinned file and needs to be fput()'ed at a later point.
*/
static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page,
struct file **fpin)
@ -2295,9 +2306,10 @@ static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page,
if (trylock_page(page))
return 1;
*fpin = maybe_unlock_mmap_for_io(vmf, *fpin);
if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
return 0;
*fpin = maybe_unlock_mmap_for_io(vmf, *fpin);
if (vmf->flags & FAULT_FLAG_KILLABLE) {
if (__lock_page_killable(page)) {
/*
@ -2317,8 +2329,11 @@ static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page,
/*
* Synchronous readahead happens when we don't even find
* a page in the page cache at all.
* Synchronous readahead happens when we don't even find a page in the page
* cache at all. We don't want to perform IO under the mmap sem, so if we have
* to drop the mmap sem we return the file that was pinned in order for us to do
* that. If we didn't pin a file then we return NULL. The file that is
* returned needs to be fput()'ed when we're done with it.
*/
static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
{
@ -2365,7 +2380,8 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
/*
* Asynchronous readahead happens when we find the page and PG_readahead,
* so we want to possibly extend the readahead further..
* so we want to possibly extend the readahead further. We return the file that
* was pinned if we have to drop the mmap_sem in order to do IO.
*/
static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
struct page *page)
@ -2441,22 +2457,23 @@ int filemap_fault(struct vm_fault *vmf)
fpin = do_async_mmap_readahead(vmf, page);
} else if (!page) {
/* No page in the page cache at all */
fpin = do_sync_mmap_readahead(vmf);
count_vm_event(PGMAJFAULT);
count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
ret = VM_FAULT_MAJOR;
fpin = do_sync_mmap_readahead(vmf);
retry_find:
page = pagecache_get_page(mapping, offset,
FGP_CREAT|FGP_FOR_MMAP,
vmf->gfp_mask);
if (!page)
if (!page) {
if (fpin)
goto out_retry;
return VM_FAULT_OOM;
}
}
if (!lock_page_maybe_drop_mmap(vmf, page, &fpin)) {
put_page(page);
return ret | VM_FAULT_RETRY;
}
if (!lock_page_maybe_drop_mmap(vmf, page, &fpin))
goto out_retry;
/* Did it get truncated? */
if (unlikely(page->mapping != mapping)) {