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Subject[PATCH v3 2/6] gfs2: Replace kmap_atomic()+memcpy by memcpy_from_page()
kmap_atomic() is deprecated in favor of kmap_local_{folio,page}().

kmap_atomic() disables page-faults and preemption (the latter only for
!PREEMPT_RT kernels), However, the code within the mapping/un-mapping in
gfs2_internal_read() does not depend on the above-mentioned side effects.

Further, memcpy_{from,to}_page() wrappers combine the
{kmap, unmap}_local_page() blocks when they are intended exclusively to
copy contents from/to the temporary mapped page. So, replace the
kmap_atomic()/kunmap_automic() block by the memcpy_from_page() API call.
This change allows to tidy-up code and also eliminate unused variable p.

Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Deepak R Varma <drv@mailo.com>
---
Changes in v3:
- Split as a separate patch for conversion in gfs2_internal_read()
- Use memcpy_from_page() as suggested by Fabio and Andreas G
- Included split version in patch set

Changes in v2:
- Update patch description to correct the replacement function name
from kmap_local_folio to kmap_local _page



fs/gfs2/aops.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
index 3eac4f2f5c27..f47fed657763 100644
--- a/fs/gfs2/aops.c
+++ b/fs/gfs2/aops.c
@@ -489,7 +489,6 @@ int gfs2_internal_read(struct gfs2_inode *ip, char *buf, loff_t *pos,
unsigned copied = 0;
unsigned amt;
struct page *page;
- void *p;

do {
page = read_cache_page(mapping, index, gfs2_read_folio, NULL);
@@ -498,12 +497,12 @@ int gfs2_internal_read(struct gfs2_inode *ip, char *buf, loff_t *pos,
continue;
return PTR_ERR(page);
}
- p = kmap_atomic(page);
- amt = size - copied;
if (offset + size > PAGE_SIZE)
amt = PAGE_SIZE - offset;
- memcpy(buf + copied, p + offset, amt);
- kunmap_atomic(p);
+ else
+ amt = size - copied;
+
+ memcpy_from_page(buf, page, offset, amt);
put_page(page);
copied += amt;
index++;
--
2.34.1


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