From: Kairui Song <[email protected]>
This series cleanup some code path, saves a few cycles and reduce the
object size by a bit, also fixes some rare race issue of statistics.
Update from V1:
- Collect Huang, Ying's Reviewd-by.
- Use bloat-o-meter to show size change info in commit message as
suggested by Matthew Wilcox.
- Rework patch 4/4 as suggested by Huang, Ying.
- Drop a previouly invalid clean up patch.
Kairui Song (4):
swapfile: get rid of volatile and avoid redundant read
swap: avoid a redundant pte map if ra window is 1
swap: fold swap_ra_clamp_pfn into swap_ra_info
swap: avoid holding swap reference in swap_cache_get_folio
mm/shmem.c | 11 +++++++++
mm/swap_state.c | 59 +++++++++++++++++++------------------------------
mm/swapfile.c | 7 +++---
3 files changed, 38 insertions(+), 39 deletions(-)
--
2.35.2
From: Kairui Song <[email protected]>
All its callers either already hold a reference to, or lock the
swap device while calling this function. There is only one exception
in shmem_swapin_folio, just make this caller also hold a reference
of the swap device, so this helper can be simplified and saves
a few cycles.
This also provides finer control of error handling in shmem_swapin_folio,
on race (with swap off), it can just try again. For invalid swap entry,
it can fail with a proper error code.
Signed-off-by: Kairui Song <[email protected]>
---
mm/shmem.c | 11 +++++++++++
mm/swap_state.c | 8 ++------
2 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index c301487be5fb..5bdf7298d494 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1735,6 +1735,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
struct address_space *mapping = inode->i_mapping;
struct shmem_inode_info *info = SHMEM_I(inode);
struct mm_struct *charge_mm = vma ? vma->vm_mm : NULL;
+ struct swap_info_struct *si;
struct folio *folio = NULL;
swp_entry_t swap;
int error;
@@ -1746,6 +1747,14 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
if (is_swapin_error_entry(swap))
return -EIO;
+ si = get_swap_device(swap);
+ if (!si) {
+ if (!shmem_confirm_swap(mapping, index, swap))
+ return -EEXIST;
+ else
+ return -EINVAL;
+ }
+
/* Look it up and read it in.. */
folio = swap_cache_get_folio(swap, NULL, 0);
if (!folio) {
@@ -1806,6 +1815,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
delete_from_swap_cache(folio);
folio_mark_dirty(folio);
swap_free(swap);
+ put_swap_device(si);
*foliop = folio;
return 0;
@@ -1819,6 +1829,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
folio_unlock(folio);
folio_put(folio);
}
+ put_swap_device(si);
return error;
}
diff --git a/mm/swap_state.c b/mm/swap_state.c
index d8d171195a3a..cb9aaa00951d 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -321,19 +321,15 @@ static inline bool swap_use_vma_readahead(void)
* unlocked and with its refcount incremented - we rely on the kernel
* lock getting page table operations atomic even if we drop the folio
* lock before returning.
+ *
+ * Caller must lock the swap device or hold a reference to keep it valid.
*/
struct folio *swap_cache_get_folio(swp_entry_t entry,
struct vm_area_struct *vma, unsigned long addr)
{
struct folio *folio;
- struct swap_info_struct *si;
- si = get_swap_device(entry);
- if (!si)
- return NULL;
folio = filemap_get_folio(swap_address_space(entry), swp_offset(entry));
- put_swap_device(si);
-
if (folio) {
bool vma_ra = swap_use_vma_readahead();
bool readahead;
--
2.35.2
From: Kairui Song <[email protected]>
Avoid a redundant pte map/unmap when swap readahead window is 1.
Signed-off-by: Kairui Song <[email protected]>
Reviewed-by: "Huang, Ying" <[email protected]>
---
mm/swap_state.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 2927507b43d8..af8bc123b7c4 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -727,8 +727,6 @@ static void swap_ra_info(struct vm_fault *vmf,
}
faddr = vmf->address;
- orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
-
fpfn = PFN_DOWN(faddr);
ra_val = GET_SWAP_RA_VAL(vma);
pfn = PFN_DOWN(SWAP_RA_ADDR(ra_val));
@@ -739,12 +737,11 @@ static void swap_ra_info(struct vm_fault *vmf,
atomic_long_set(&vma->swap_readahead_info,
SWAP_RA_VAL(faddr, win, 0));
- if (win == 1) {
- pte_unmap(orig_pte);
+ if (win == 1)
return;
- }
/* Copy the PTEs because the page table may be unmapped */
+ orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
if (fpfn == pfn + 1)
swap_ra_clamp_pfn(vma, faddr, fpfn, fpfn + win, &start, &end);
else if (pfn == fpfn + 1)
--
2.35.2