| Message ID | 20231127154601.585849-1-fabio.maria.de.francesco@linux.intel.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | None | expand |
Please discard this patch for a mistake in the subject. Fabio On Monday, 27 November 2023 16:45:53 CET Fabio M. De Francesco wrote: > kmap_atomic() has been deprecated in favor of kmap_local_page(). > > Therefore, replace kmap_atomic() with kmap_local_page() in > swapfile.c. > > kmap_atomic() is implemented like a kmap_local_page() which also > disables page-faults and preemption (the latter only in !PREEMPT_RT > kernels). The kernel virtual addresses returned by these two API are > only valid in the context of the callers (i.e., they cannot be handed to > other threads). > > With kmap_local_page() the mappings are per thread and CPU local like > in kmap_atomic(); however, they can handle page-faults and can be called > from any context (including interrupts). The tasks that call > kmap_local_page() can be preempted and, when they are scheduled to run > again, the kernel virtual addresses are restored and are still valid. > > In mm/swapfile.c, the blocks of code between the mappings and un-mappings > do not depend on the above-mentioned side effects of kmap_aatomic(), so > that the mere replacements of the old API with the new one is all that is > required (i.e., there is no need to explicitly call pagefault_disable() > and/or preempt_disable()). > > Cc: Ira Weiny <ira.weiny@intel.com> > Signed-off-by: Fabio M. De Francesco > <fabio.maria.de.francesco@linux.intel.com> --- > mm/swapfile.c | 34 +++++++++++++++++----------------- > 1 file changed, 17 insertions(+), 17 deletions(-) > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 4bc70f459164..8be70912e298 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -1495,9 +1495,9 @@ int swp_swapcount(swp_entry_t entry) > > do { > page = list_next_entry(page, lru); > - map = kmap_atomic(page); > + map = kmap_local_page(page); > tmp_count = map[offset]; > - kunmap_atomic(map); > + kunmap_local(map); > > count += (tmp_count & ~COUNT_CONTINUED) * n; > n *= (SWAP_CONT_MAX + 1); > @@ -3477,9 +3477,9 @@ int add_swap_count_continuation(swp_entry_t entry, > gfp_t gfp_mask) if (!(count & COUNT_CONTINUED)) > goto out_unlock_cont; > > - map = kmap_atomic(list_page) + offset; > + map = kmap_local_page(list_page) + offset; > count = *map; > - kunmap_atomic(map); > + kunmap_local(map); > > /* > * If this continuation count now has some space in it, > @@ -3529,7 +3529,7 @@ static bool swap_count_continued(struct > swap_info_struct *si, spin_lock(&si->cont_lock); > offset &= ~PAGE_MASK; > page = list_next_entry(head, lru); > - map = kmap_atomic(page) + offset; > + map = kmap_local_page(page) + offset; > > if (count == SWAP_MAP_MAX) /* initial increment from swap_map */ > goto init_map; /* jump over SWAP_CONT_MAX checks */ > @@ -3539,27 +3539,27 @@ static bool swap_count_continued(struct > swap_info_struct *si, * Think of how you add 1 to 999 > */ > while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) { > - kunmap_atomic(map); > + kunmap_local(map); > page = list_next_entry(page, lru); > BUG_ON(page == head); > - map = kmap_atomic(page) + offset; > + map = kmap_local_page(page) + offset; > } > if (*map == SWAP_CONT_MAX) { > - kunmap_atomic(map); > + kunmap_local(map); > page = list_next_entry(page, lru); > if (page == head) { > ret = false; /* add count continuation */ > goto out; > } > - map = kmap_atomic(page) + offset; > + map = kmap_local_page(page) + offset; > init_map: *map = 0; /* we didn't zero the page */ > } > *map += 1; > - kunmap_atomic(map); > + kunmap_local(map); > while ((page = list_prev_entry(page, lru)) != head) { > - map = kmap_atomic(page) + offset; > + map = kmap_local_page(page) + offset; > *map = COUNT_CONTINUED; > - kunmap_atomic(map); > + kunmap_local(map); > } > ret = true; /* incremented */ > > @@ -3569,21 +3569,21 @@ init_map: *map = 0; /* we didn't zero the page */ > */ > BUG_ON(count != COUNT_CONTINUED); > while (*map == COUNT_CONTINUED) { > - kunmap_atomic(map); > + kunmap_local(map); > page = list_next_entry(page, lru); > BUG_ON(page == head); > - map = kmap_atomic(page) + offset; > + map = kmap_local_page(page) + offset; > } > BUG_ON(*map == 0); > *map -= 1; > if (*map == 0) > count = 0; > - kunmap_atomic(map); > + kunmap_local(map); > while ((page = list_prev_entry(page, lru)) != head) { > - map = kmap_atomic(page) + offset; > + map = kmap_local_page(page) + offset; > *map = SWAP_CONT_MAX | count; > count = COUNT_CONTINUED; > - kunmap_atomic(map); > + kunmap_local(map); > } > ret = count == COUNT_CONTINUED; > }
diff --git a/mm/swapfile.c b/mm/swapfile.c index 4bc70f459164..8be70912e298 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1495,9 +1495,9 @@ int swp_swapcount(swp_entry_t entry) do { page = list_next_entry(page, lru); - map = kmap_atomic(page); + map = kmap_local_page(page); tmp_count = map[offset]; - kunmap_atomic(map); + kunmap_local(map); count += (tmp_count & ~COUNT_CONTINUED) * n; n *= (SWAP_CONT_MAX + 1); @@ -3477,9 +3477,9 @@ int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask) if (!(count & COUNT_CONTINUED)) goto out_unlock_cont; - map = kmap_atomic(list_page) + offset; + map = kmap_local_page(list_page) + offset; count = *map; - kunmap_atomic(map); + kunmap_local(map); /* * If this continuation count now has some space in it, @@ -3529,7 +3529,7 @@ static bool swap_count_continued(struct swap_info_struct *si, spin_lock(&si->cont_lock); offset &= ~PAGE_MASK; page = list_next_entry(head, lru); - map = kmap_atomic(page) + offset; + map = kmap_local_page(page) + offset; if (count == SWAP_MAP_MAX) /* initial increment from swap_map */ goto init_map; /* jump over SWAP_CONT_MAX checks */ @@ -3539,27 +3539,27 @@ static bool swap_count_continued(struct swap_info_struct *si, * Think of how you add 1 to 999 */ while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) { - kunmap_atomic(map); + kunmap_local(map); page = list_next_entry(page, lru); BUG_ON(page == head); - map = kmap_atomic(page) + offset; + map = kmap_local_page(page) + offset; } if (*map == SWAP_CONT_MAX) { - kunmap_atomic(map); + kunmap_local(map); page = list_next_entry(page, lru); if (page == head) { ret = false; /* add count continuation */ goto out; } - map = kmap_atomic(page) + offset; + map = kmap_local_page(page) + offset; init_map: *map = 0; /* we didn't zero the page */ } *map += 1; - kunmap_atomic(map); + kunmap_local(map); while ((page = list_prev_entry(page, lru)) != head) { - map = kmap_atomic(page) + offset; + map = kmap_local_page(page) + offset; *map = COUNT_CONTINUED; - kunmap_atomic(map); + kunmap_local(map); } ret = true; /* incremented */ @@ -3569,21 +3569,21 @@ init_map: *map = 0; /* we didn't zero the page */ */ BUG_ON(count != COUNT_CONTINUED); while (*map == COUNT_CONTINUED) { - kunmap_atomic(map); + kunmap_local(map); page = list_next_entry(page, lru); BUG_ON(page == head); - map = kmap_atomic(page) + offset; + map = kmap_local_page(page) + offset; } BUG_ON(*map == 0); *map -= 1; if (*map == 0) count = 0; - kunmap_atomic(map); + kunmap_local(map); while ((page = list_prev_entry(page, lru)) != head) { - map = kmap_atomic(page) + offset; + map = kmap_local_page(page) + offset; *map = SWAP_CONT_MAX | count; count = COUNT_CONTINUED; - kunmap_atomic(map); + kunmap_local(map); } ret = count == COUNT_CONTINUED; }
kmap_atomic() has been deprecated in favor of kmap_local_page(). Therefore, replace kmap_atomic() with kmap_local_page() in swapfile.c. kmap_atomic() is implemented like a kmap_local_page() which also disables page-faults and preemption (the latter only in !PREEMPT_RT kernels). The kernel virtual addresses returned by these two API are only valid in the context of the callers (i.e., they cannot be handed to other threads). With kmap_local_page() the mappings are per thread and CPU local like in kmap_atomic(); however, they can handle page-faults and can be called from any context (including interrupts). The tasks that call kmap_local_page() can be preempted and, when they are scheduled to run again, the kernel virtual addresses are restored and are still valid. In mm/swapfile.c, the blocks of code between the mappings and un-mappings do not depend on the above-mentioned side effects of kmap_aatomic(), so that the mere replacements of the old API with the new one is all that is required (i.e., there is no need to explicitly call pagefault_disable() and/or preempt_disable()). Cc: Ira Weiny <ira.weiny@intel.com> Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com> --- mm/swapfile.c | 34 +++++++++++++++++----------------- 1 file changed, 17 insertions(+), 17 deletions(-)