#include <linux/uio.h>
#include <linux/khugepaged.h>
#include <linux/hugetlb.h>
+#include <linux/frontswap.h>
#include <asm/tlbflush.h> /* for arch/microblaze update_mmu_cache() */
clear_inode(inode);
}
-static unsigned long find_swap_entry(struct xarray *xa, void *item)
+extern struct swap_info_struct *swap_info[];
+
+static int shmem_find_swap_entries(struct address_space *mapping,
+ pgoff_t start, unsigned int nr_entries,
+ struct page **entries, pgoff_t *indices,
+ bool frontswap)
{
- XA_STATE(xas, xa, 0);
- unsigned int checked = 0;
- void *entry;
+ XA_STATE(xas, &mapping->i_pages, start);
+ struct page *page;
+ unsigned int ret = 0;
+
+ if (!nr_entries)
+ return 0;
rcu_read_lock();
- xas_for_each(&xas, entry, ULONG_MAX) {
- if (xas_retry(&xas, entry))
+ xas_for_each(&xas, page, ULONG_MAX) {
+ if (xas_retry(&xas, page))
continue;
- if (entry == item)
- break;
- checked++;
- if ((checked % XA_CHECK_SCHED) != 0)
+
+ if (!xa_is_value(page))
continue;
- xas_pause(&xas);
- cond_resched_rcu();
+
+ if (frontswap) {
+ swp_entry_t entry = radix_to_swp_entry(page);
+
+ if (!frontswap_test(swap_info[swp_type(entry)],
+ swp_offset(entry)))
+ continue;
+ }
+
+ indices[ret] = xas.xa_index;
+ entries[ret] = page;
+
+ if (need_resched()) {
+ xas_pause(&xas);
+ cond_resched_rcu();
+ }
+ if (++ret == nr_entries)
+ break;
}
rcu_read_unlock();
- return entry ? xas.xa_index : -1;
+ return ret;
}
/*
- * If swap found in inode, free it and move page from swapcache to filecache.
+ * Move the swapped pages for an inode to page cache. Returns the count
+ * of pages swapped in, or the error in case of failure.
*/
-static int shmem_unuse_inode(struct shmem_inode_info *info,
- swp_entry_t swap, struct page **pagep)
+static int shmem_unuse_swap_entries(struct inode *inode, struct pagevec pvec,
+ pgoff_t *indices)
{
- struct address_space *mapping = info->vfs_inode.i_mapping;
- void *radswap;
- pgoff_t index;
- gfp_t gfp;
+ int i = 0;
+ int ret = 0;
int error = 0;
+ struct address_space *mapping = inode->i_mapping;
- radswap = swp_to_radix_entry(swap);
- index = find_swap_entry(&mapping->i_pages, radswap);
- if (index == -1)
- return -EAGAIN; /* tell shmem_unuse we found nothing */
-
- /*
- * Move _head_ to start search for next from here.
- * But be careful: shmem_evict_inode checks list_empty without taking
- * mutex, and there's an instant in list_move_tail when info->swaplist
- * would appear empty, if it were the only one on shmem_swaplist.
- */
- if (shmem_swaplist.next != &info->swaplist)
- list_move_tail(&shmem_swaplist, &info->swaplist);
+ for (i = 0; i < pvec.nr; i++) {
+ struct page *page = pvec.pages[i];
- gfp = mapping_gfp_mask(mapping);
- if (shmem_should_replace_page(*pagep, gfp)) {
- mutex_unlock(&shmem_swaplist_mutex);
- error = shmem_replace_page(pagep, gfp, info, index);
- mutex_lock(&shmem_swaplist_mutex);
- /*
- * We needed to drop mutex to make that restrictive page
- * allocation, but the inode might have been freed while we
- * dropped it: although a racing shmem_evict_inode() cannot
- * complete without emptying the page cache, our page lock
- * on this swapcache page is not enough to prevent that -
- * free_swap_and_cache() of our swap entry will only
- * trylock_page(), removing swap from page cache whatever.
- *
- * We must not proceed to shmem_add_to_page_cache() if the
- * inode has been freed, but of course we cannot rely on
- * inode or mapping or info to check that. However, we can
- * safely check if our swap entry is still in use (and here
- * it can't have got reused for another page): if it's still
- * in use, then the inode cannot have been freed yet, and we
- * can safely proceed (if it's no longer in use, that tells
- * nothing about the inode, but we don't need to unuse swap).
- */
- if (!page_swapcount(*pagep))
- error = -ENOENT;
+ if (!xa_is_value(page))
+ continue;
+ error = shmem_swapin_page(inode, indices[i],
+ &page, SGP_CACHE,
+ mapping_gfp_mask(mapping),
+ NULL, NULL);
+ if (error == 0) {
+ unlock_page(page);
+ put_page(page);
+ ret++;
+ }
+ if (error == -ENOMEM)
+ break;
+ error = 0;
}
+ return error ? error : ret;
+}
- /*
- * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
- * but also to hold up shmem_evict_inode(): so inode cannot be freed
- * beneath us (pagelock doesn't help until the page is in pagecache).
- */
- if (!error)
- error = shmem_add_to_page_cache(*pagep, mapping, index,
- radswap, gfp);
- if (error != -ENOMEM) {
- /*
- * Truncation and eviction use free_swap_and_cache(), which
- * only does trylock page: if we raced, best clean up here.
- */
- delete_from_swap_cache(*pagep);
- set_page_dirty(*pagep);
- if (!error) {
- spin_lock_irq(&info->lock);
- info->swapped--;
- spin_unlock_irq(&info->lock);
- swap_free(swap);
+/*
+ * If swap found in inode, free it and move page from swapcache to filecache.
+ */
+static int shmem_unuse_inode(struct inode *inode, unsigned int type,
+ bool frontswap, unsigned long *fs_pages_to_unuse)
+{
+ struct address_space *mapping = inode->i_mapping;
+ pgoff_t start = 0;
+ struct pagevec pvec;
+ pgoff_t indices[PAGEVEC_SIZE];
+ bool frontswap_partial = (frontswap && *fs_pages_to_unuse > 0);
+ int ret = 0;
+
+ pagevec_init(&pvec);
+ do {
+ unsigned int nr_entries = PAGEVEC_SIZE;
+
+ if (frontswap_partial && *fs_pages_to_unuse < PAGEVEC_SIZE)
+ nr_entries = *fs_pages_to_unuse;
+
+ pvec.nr = shmem_find_swap_entries(mapping, start, nr_entries,
+ pvec.pages, indices,
+ frontswap);
+ if (pvec.nr == 0) {
+ ret = 0;
+ break;
}
- }
- return error;
+
+ ret = shmem_unuse_swap_entries(inode, pvec, indices);
+ if (ret < 0)
+ break;
+
+ if (frontswap_partial) {
+ *fs_pages_to_unuse -= ret;
+ if (*fs_pages_to_unuse == 0) {
+ ret = FRONTSWAP_PAGES_UNUSED;
+ break;
+ }
+ }
+
+ start = indices[pvec.nr - 1];
+ } while (true);
+
+ return ret;
}
/*
- * Search through swapped inodes to find and replace swap by page.
+ * Read all the shared memory data that resides in the swap
+ * device 'type' back into memory, so the swap device can be
+ * unused.
*/
-int shmem_unuse(swp_entry_t swap, struct page *page)
+int shmem_unuse(unsigned int type, bool frontswap,
+ unsigned long *fs_pages_to_unuse)
{
- struct list_head *this, *next;
- struct shmem_inode_info *info;
- struct mem_cgroup *memcg;
+ struct shmem_inode_info *info, *next;
+ struct inode *inode;
+ struct inode *prev_inode = NULL;
int error = 0;
- /*
- * There's a faint possibility that swap page was replaced before
- * caller locked it: caller will come back later with the right page.
- */
- if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
- goto out;
+ if (list_empty(&shmem_swaplist))
+ return 0;
+
+ mutex_lock(&shmem_swaplist_mutex);
/*
- * Charge page using GFP_KERNEL while we can wait, before taking
- * the shmem_swaplist_mutex which might hold up shmem_writepage().
- * Charged back to the user (not to caller) when swap account is used.
+ * The extra refcount on the inode is necessary to safely dereference
+ * p->next after re-acquiring the lock. New shmem inodes with swap
+ * get added to the end of the list and we will scan them all.
*/
- error = mem_cgroup_try_charge_delay(page, current->mm, GFP_KERNEL,
- &memcg, false);
- if (error)
- goto out;
- /* No memory allocation: swap entry occupies the slot for the page */
- error = -EAGAIN;
-
- mutex_lock(&shmem_swaplist_mutex);
- list_for_each_safe(this, next, &shmem_swaplist) {
- info = list_entry(this, struct shmem_inode_info, swaplist);
- if (info->swapped)
- error = shmem_unuse_inode(info, swap, &page);
- else
+ list_for_each_entry_safe(info, next, &shmem_swaplist, swaplist) {
+ if (!info->swapped) {
list_del_init(&info->swaplist);
+ continue;
+ }
+
+ inode = igrab(&info->vfs_inode);
+ if (!inode)
+ continue;
+
+ mutex_unlock(&shmem_swaplist_mutex);
+ if (prev_inode)
+ iput(prev_inode);
+ prev_inode = inode;
+
+ error = shmem_unuse_inode(inode, type, frontswap,
+ fs_pages_to_unuse);
cond_resched();
- if (error != -EAGAIN)
+
+ mutex_lock(&shmem_swaplist_mutex);
+ next = list_next_entry(info, swaplist);
+ if (!info->swapped)
+ list_del_init(&info->swaplist);
+ if (error)
break;
- /* found nothing in this: move on to search the next */
}
mutex_unlock(&shmem_swaplist_mutex);
- if (error) {
- if (error != -ENOMEM)
- error = 0;
- mem_cgroup_cancel_charge(page, memcg, false);
- } else
- mem_cgroup_commit_charge(page, memcg, true, false);
-out:
- unlock_page(page);
- put_page(page);
+ if (prev_inode)
+ iput(prev_inode);
+
return error;
}
*/
mutex_lock(&shmem_swaplist_mutex);
if (list_empty(&info->swaplist))
- list_add_tail(&info->swaplist, &shmem_swaplist);
+ list_add(&info->swaplist, &shmem_swaplist);
if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
spin_lock_irq(&info->lock);
return 0;
}
-int shmem_unuse(swp_entry_t swap, struct page *page)
+int shmem_unuse(unsigned int type, bool frontswap,
+ unsigned long *fs_pages_to_unuse)
{
return 0;
}
}
static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
- unsigned long addr, unsigned long end,
- swp_entry_t entry, struct page *page)
+ unsigned long addr, unsigned long end,
+ unsigned int type, bool frontswap,
+ unsigned long *fs_pages_to_unuse)
{
- pte_t swp_pte = swp_entry_to_pte(entry);
+ struct page *page;
+ swp_entry_t entry;
pte_t *pte;
+ struct swap_info_struct *si;
+ unsigned long offset;
int ret = 0;
+ volatile unsigned char *swap_map;
- /*
- * We don't actually need pte lock while scanning for swp_pte: since
- * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
- * page table while we're scanning; though it could get zapped, and on
- * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
- * of unmatched parts which look like swp_pte, so unuse_pte must
- * recheck under pte lock. Scanning without pte lock lets it be
- * preemptable whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
- */
+ si = swap_info[type];
pte = pte_offset_map(pmd, addr);
do {
- /*
- * swapoff spends a _lot_ of time in this loop!
- * Test inline before going to call unuse_pte.
- */
- if (unlikely(pte_same_as_swp(*pte, swp_pte))) {
- pte_unmap(pte);
- ret = unuse_pte(vma, pmd, addr, entry, page);
- if (ret)
- goto out;
- pte = pte_offset_map(pmd, addr);
+ struct vm_fault vmf;
+
+ if (!is_swap_pte(*pte))
+ continue;
+
+ entry = pte_to_swp_entry(*pte);
+ if (swp_type(entry) != type)
+ continue;
+
+ offset = swp_offset(entry);
+ if (frontswap && !frontswap_test(si, offset))
+ continue;
+
+ pte_unmap(pte);
+ swap_map = &si->swap_map[offset];
+ vmf.vma = vma;
+ vmf.address = addr;
+ vmf.pmd = pmd;
+ page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE, &vmf);
+ if (!page) {
+ if (*swap_map == 0 || *swap_map == SWAP_MAP_BAD)
+ goto try_next;
+ return -ENOMEM;
+ }
+
+ lock_page(page);
+ wait_on_page_writeback(page);
+ ret = unuse_pte(vma, pmd, addr, entry, page);
+ if (ret < 0) {
+ unlock_page(page);
+ put_page(page);
+ goto out;
+ }
+
+ try_to_free_swap(page);
+ unlock_page(page);
+ put_page(page);
+
+ if (*fs_pages_to_unuse && !--(*fs_pages_to_unuse)) {
+ ret = FRONTSWAP_PAGES_UNUSED;
+ goto out;
}
+try_next:
+ pte = pte_offset_map(pmd, addr);
} while (pte++, addr += PAGE_SIZE, addr != end);
pte_unmap(pte - 1);
+
+ ret = 0;
out:
return ret;
}
static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
unsigned long addr, unsigned long end,
- swp_entry_t entry, struct page *page)
+ unsigned int type, bool frontswap,
+ unsigned long *fs_pages_to_unuse)
{
pmd_t *pmd;
unsigned long next;
next = pmd_addr_end(addr, end);
if (pmd_none_or_trans_huge_or_clear_bad(pmd))
continue;
- ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
+ ret = unuse_pte_range(vma, pmd, addr, next, type,
+ frontswap, fs_pages_to_unuse);
if (ret)
return ret;
} while (pmd++, addr = next, addr != end);
static inline int unuse_pud_range(struct vm_area_struct *vma, p4d_t *p4d,
unsigned long addr, unsigned long end,
- swp_entry_t entry, struct page *page)
+ unsigned int type, bool frontswap,
+ unsigned long *fs_pages_to_unuse)
{
pud_t *pud;
unsigned long next;
next = pud_addr_end(addr, end);
if (pud_none_or_clear_bad(pud))
continue;
- ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
+ ret = unuse_pmd_range(vma, pud, addr, next, type,
+ frontswap, fs_pages_to_unuse);
if (ret)
return ret;
} while (pud++, addr = next, addr != end);
static inline int unuse_p4d_range(struct vm_area_struct *vma, pgd_t *pgd,
unsigned long addr, unsigned long end,
- swp_entry_t entry, struct page *page)
+ unsigned int type, bool frontswap,
+ unsigned long *fs_pages_to_unuse)
{
p4d_t *p4d;
unsigned long next;
next = p4d_addr_end(addr, end);
if (p4d_none_or_clear_bad(p4d))
continue;
- ret = unuse_pud_range(vma, p4d, addr, next, entry, page);
+ ret = unuse_pud_range(vma, p4d, addr, next, type,
+ frontswap, fs_pages_to_unuse);
if (ret)
return ret;
} while (p4d++, addr = next, addr != end);
return 0;
}
-static int unuse_vma(struct vm_area_struct *vma,
- swp_entry_t entry, struct page *page)
+static int unuse_vma(struct vm_area_struct *vma, unsigned int type,
+ bool frontswap, unsigned long *fs_pages_to_unuse)
{
pgd_t *pgd;
unsigned long addr, end, next;
int ret;
- if (page_anon_vma(page)) {
- addr = page_address_in_vma(page, vma);
- if (addr == -EFAULT)
- return 0;
- else
- end = addr + PAGE_SIZE;
- } else {
- addr = vma->vm_start;
- end = vma->vm_end;
- }
+ addr = vma->vm_start;
+ end = vma->vm_end;
pgd = pgd_offset(vma->vm_mm, addr);
do {
next = pgd_addr_end(addr, end);
if (pgd_none_or_clear_bad(pgd))
continue;
- ret = unuse_p4d_range(vma, pgd, addr, next, entry, page);
+ ret = unuse_p4d_range(vma, pgd, addr, next, type,
+ frontswap, fs_pages_to_unuse);
if (ret)
return ret;
} while (pgd++, addr = next, addr != end);
return 0;
}
-static int unuse_mm(struct mm_struct *mm,
- swp_entry_t entry, struct page *page)
+static int unuse_mm(struct mm_struct *mm, unsigned int type,
+ bool frontswap, unsigned long *fs_pages_to_unuse)
{
struct vm_area_struct *vma;
int ret = 0;
- if (!down_read_trylock(&mm->mmap_sem)) {
- /*
- * Activate page so shrink_inactive_list is unlikely to unmap
- * its ptes while lock is dropped, so swapoff can make progress.
- */
- activate_page(page);
- unlock_page(page);
- down_read(&mm->mmap_sem);
- lock_page(page);
- }
+ down_read(&mm->mmap_sem);
for (vma = mm->mmap; vma; vma = vma->vm_next) {
- if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
- break;
+ if (vma->anon_vma) {
+ ret = unuse_vma(vma, type, frontswap,
+ fs_pages_to_unuse);
+ if (ret)
+ break;
+ }
cond_resched();
}
up_read(&mm->mmap_sem);
- return (ret < 0)? ret: 0;
+ return ret;
}
/*
* Scan swap_map (or frontswap_map if frontswap parameter is true)
- * from current position to next entry still in use.
- * Recycle to start on reaching the end, returning 0 when empty.
+ * from current position to next entry still in use. Return 0
+ * if there are no inuse entries after prev till end of the map.
*/
static unsigned int find_next_to_unuse(struct swap_info_struct *si,
unsigned int prev, bool frontswap)
{
- unsigned int max = si->max;
- unsigned int i = prev;
+ unsigned int i;
unsigned char count;
/*
* hits are okay, and sys_swapoff() has already prevented new
* allocations from this area (while holding swap_lock).
*/
- for (;;) {
- if (++i >= max) {
- if (!prev) {
- i = 0;
- break;
- }
- /*
- * No entries in use at top of swap_map,
- * loop back to start and recheck there.
- */
- max = prev + 1;
- prev = 0;
- i = 1;
- }
+ for (i = prev + 1; i < si->max; i++) {
count = READ_ONCE(si->swap_map[i]);
if (count && swap_count(count) != SWAP_MAP_BAD)
if (!frontswap || frontswap_test(si, i))
if ((i % LATENCY_LIMIT) == 0)
cond_resched();
}
+
+ if (i == si->max)
+ i = 0;
+
return i;
}
/*
- * We completely avoid races by reading each swap page in advance,
- * and then search for the process using it. All the necessary
- * page table adjustments can then be made atomically.
- *
- * if the boolean frontswap is true, only unuse pages_to_unuse pages;
+ * If the boolean frontswap is true, only unuse pages_to_unuse pages;
* pages_to_unuse==0 means all pages; ignored if frontswap is false
*/
+#define SWAP_UNUSE_MAX_TRIES 3
int try_to_unuse(unsigned int type, bool frontswap,
unsigned long pages_to_unuse)
{
+ struct mm_struct *prev_mm;
+ struct mm_struct *mm;
+ struct list_head *p;
+ int retval = 0;
struct swap_info_struct *si = swap_info[type];
- struct mm_struct *start_mm;
- volatile unsigned char *swap_map; /* swap_map is accessed without
- * locking. Mark it as volatile
- * to prevent compiler doing
- * something odd.
- */
- unsigned char swcount;
struct page *page;
swp_entry_t entry;
- unsigned int i = 0;
- int retval = 0;
+ unsigned int i;
+ int retries = 0;
- /*
- * When searching mms for an entry, a good strategy is to
- * start at the first mm we freed the previous entry from
- * (though actually we don't notice whether we or coincidence
- * freed the entry). Initialize this start_mm with a hold.
- *
- * A simpler strategy would be to start at the last mm we
- * freed the previous entry from; but that would take less
- * advantage of mmlist ordering, which clusters forked mms
- * together, child after parent. If we race with dup_mmap(), we
- * prefer to resolve parent before child, lest we miss entries
- * duplicated after we scanned child: using last mm would invert
- * that.
- */
- start_mm = &init_mm;
- mmget(&init_mm);
+ if (!si->inuse_pages)
+ return 0;
- /*
- * Keep on scanning until all entries have gone. Usually,
- * one pass through swap_map is enough, but not necessarily:
- * there are races when an instance of an entry might be missed.
- */
- while ((i = find_next_to_unuse(si, i, frontswap)) != 0) {
+ if (!frontswap)
+ pages_to_unuse = 0;
+
+retry:
+ retval = shmem_unuse(type, frontswap, &pages_to_unuse);
+ if (retval)
+ goto out;
+
+ prev_mm = &init_mm;
+ mmget(prev_mm);
+
+ spin_lock(&mmlist_lock);
+ p = &init_mm.mmlist;
+ while ((p = p->next) != &init_mm.mmlist) {
if (signal_pending(current)) {
retval = -EINTR;
break;
}
- /*
- * Get a page for the entry, using the existing swap
- * cache page if there is one. Otherwise, get a clean
- * page and read the swap into it.
- */
- swap_map = &si->swap_map[i];
- entry = swp_entry(type, i);
- page = read_swap_cache_async(entry,
- GFP_HIGHUSER_MOVABLE, NULL, 0, false);
- if (!page) {
- /*
- * Either swap_duplicate() failed because entry
- * has been freed independently, and will not be
- * reused since sys_swapoff() already disabled
- * allocation from here, or alloc_page() failed.
- */
- swcount = *swap_map;
- /*
- * We don't hold lock here, so the swap entry could be
- * SWAP_MAP_BAD (when the cluster is discarding).
- * Instead of fail out, We can just skip the swap
- * entry because swapoff will wait for discarding
- * finish anyway.
- */
- if (!swcount || swcount == SWAP_MAP_BAD)
- continue;
- retval = -ENOMEM;
- break;
- }
+ mm = list_entry(p, struct mm_struct, mmlist);
+ if (!mmget_not_zero(mm))
+ continue;
+ spin_unlock(&mmlist_lock);
+ mmput(prev_mm);
+ prev_mm = mm;
+ retval = unuse_mm(mm, type, frontswap, &pages_to_unuse);
- /*
- * Don't hold on to start_mm if it looks like exiting.
- */
- if (atomic_read(&start_mm->mm_users) == 1) {
- mmput(start_mm);
- start_mm = &init_mm;
- mmget(&init_mm);
+ if (retval) {
+ mmput(prev_mm);
+ goto out;
}
/*
- * Wait for and lock page. When do_swap_page races with
- * try_to_unuse, do_swap_page can handle the fault much
- * faster than try_to_unuse can locate the entry. This
- * apparently redundant "wait_on_page_locked" lets try_to_unuse
- * defer to do_swap_page in such a case - in some tests,
- * do_swap_page and try_to_unuse repeatedly compete.
- */
- wait_on_page_locked(page);
- wait_on_page_writeback(page);
- lock_page(page);
- wait_on_page_writeback(page);
-
- /*
- * Remove all references to entry.
+ * Make sure that we aren't completely killing
+ * interactive performance.
*/
- swcount = *swap_map;
- if (swap_count(swcount) == SWAP_MAP_SHMEM) {
- retval = shmem_unuse(entry, page);
- /* page has already been unlocked and released */
- if (retval < 0)
- break;
- continue;
- }
- if (swap_count(swcount) && start_mm != &init_mm)
- retval = unuse_mm(start_mm, entry, page);
-
- if (swap_count(*swap_map)) {
- int set_start_mm = (*swap_map >= swcount);
- struct list_head *p = &start_mm->mmlist;
- struct mm_struct *new_start_mm = start_mm;
- struct mm_struct *prev_mm = start_mm;
- struct mm_struct *mm;
-
- mmget(new_start_mm);
- mmget(prev_mm);
- spin_lock(&mmlist_lock);
- while (swap_count(*swap_map) && !retval &&
- (p = p->next) != &start_mm->mmlist) {
- mm = list_entry(p, struct mm_struct, mmlist);
- if (!mmget_not_zero(mm))
- continue;
- spin_unlock(&mmlist_lock);
- mmput(prev_mm);
- prev_mm = mm;
+ cond_resched();
+ spin_lock(&mmlist_lock);
+ }
+ spin_unlock(&mmlist_lock);
- cond_resched();
+ mmput(prev_mm);
- swcount = *swap_map;
- if (!swap_count(swcount)) /* any usage ? */
- ;
- else if (mm == &init_mm)
- set_start_mm = 1;
- else
- retval = unuse_mm(mm, entry, page);
-
- if (set_start_mm && *swap_map < swcount) {
- mmput(new_start_mm);
- mmget(mm);
- new_start_mm = mm;
- set_start_mm = 0;
- }
- spin_lock(&mmlist_lock);
- }
- spin_unlock(&mmlist_lock);
- mmput(prev_mm);
- mmput(start_mm);
- start_mm = new_start_mm;
- }
- if (retval) {
- unlock_page(page);
- put_page(page);
- break;
- }
+ i = 0;
+ while ((i = find_next_to_unuse(si, i, frontswap)) != 0) {
- /*
- * If a reference remains (rare), we would like to leave
- * the page in the swap cache; but try_to_unmap could
- * then re-duplicate the entry once we drop page lock,
- * so we might loop indefinitely; also, that page could
- * not be swapped out to other storage meanwhile. So:
- * delete from cache even if there's another reference,
- * after ensuring that the data has been saved to disk -
- * since if the reference remains (rarer), it will be
- * read from disk into another page. Splitting into two
- * pages would be incorrect if swap supported "shared
- * private" pages, but they are handled by tmpfs files.
- *
- * Given how unuse_vma() targets one particular offset
- * in an anon_vma, once the anon_vma has been determined,
- * this splitting happens to be just what is needed to
- * handle where KSM pages have been swapped out: re-reading
- * is unnecessarily slow, but we can fix that later on.
- */
- if (swap_count(*swap_map) &&
- PageDirty(page) && PageSwapCache(page)) {
- struct writeback_control wbc = {
- .sync_mode = WB_SYNC_NONE,
- };
-
- swap_writepage(compound_head(page), &wbc);
- lock_page(page);
- wait_on_page_writeback(page);
- }
+ entry = swp_entry(type, i);
+ page = find_get_page(swap_address_space(entry), i);
+ if (!page)
+ continue;
/*
* It is conceivable that a racing task removed this page from
- * swap cache just before we acquired the page lock at the top,
- * or while we dropped it in unuse_mm(). The page might even
- * be back in swap cache on another swap area: that we must not
- * delete, since it may not have been written out to swap yet.
- */
- if (PageSwapCache(page) &&
- likely(page_private(page) == entry.val) &&
- (!PageTransCompound(page) ||
- !swap_page_trans_huge_swapped(si, entry)))
- delete_from_swap_cache(compound_head(page));
-
- /*
- * So we could skip searching mms once swap count went
- * to 1, we did not mark any present ptes as dirty: must
- * mark page dirty so shrink_page_list will preserve it.
+ * swap cache just before we acquired the page lock. The page
+ * might even be back in swap cache on another swap area. But
+ * that is okay, try_to_free_swap() only removes stale pages.
*/
- SetPageDirty(page);
+ lock_page(page);
+ wait_on_page_writeback(page);
+ try_to_free_swap(page);
unlock_page(page);
put_page(page);
/*
- * Make sure that we aren't completely killing
- * interactive performance.
+ * For frontswap, we just need to unuse pages_to_unuse, if
+ * it was specified. Need not check frontswap again here as
+ * we already zeroed out pages_to_unuse if not frontswap.
*/
- cond_resched();
- if (frontswap && pages_to_unuse > 0) {
- if (!--pages_to_unuse)
- break;
- }
+ if (pages_to_unuse && --pages_to_unuse == 0)
+ goto out;
}
- mmput(start_mm);
- return retval;
+ /*
+ * Lets check again to see if there are still swap entries in the map.
+ * If yes, we would need to do retry the unuse logic again.
+ * Under global memory pressure, swap entries can be reinserted back
+ * into process space after the mmlist loop above passes over them.
+ * Its not worth continuosuly retrying to unuse the swap in this case.
+ * So we try SWAP_UNUSE_MAX_TRIES times.
+ */
+ if (++retries >= SWAP_UNUSE_MAX_TRIES)
+ retval = -EBUSY;
+ else if (si->inuse_pages)
+ goto retry;
+
+out:
+ return (retval == FRONTSWAP_PAGES_UNUSED) ? 0 : retval;
}
/*
projects / users / hch / block.git / commitdiff