Docs/admin-guide/mm/pagemap: wordsmith page flags descriptions

Some descriptions of page flags in 'pagemap.rst' are written in
assumption of none-rst, which respects every new line, as below:

7 - SLAB
page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator
When compound page is used, SLUB/SLQB will only set this flag on the head

Because rst ignores the new line between the first sentence and second
sentence, resulting html looks a little bit weird, as below.

7 - SLAB
page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator When
^
compound page is used, SLUB/SLQB will only set this flag on the head
page; SLOB will not flag it at all.

This change makes it more natural and consistent with other parts in the
rendered version.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: SeongJae Park <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Cc: Peter Xu <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/admin-guide/mm/pagemap.rst

···
 ====================================
 
 0 - LOCKED
-   page is being locked for exclusive access, e.g. by undergoing read/write IO
+   The page is being locked for exclusive access, e.g. by undergoing read/write
+   IO.
 7 - SLAB
-   page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator
+   The page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator.
    When compound page is used, SLUB/SLQB will only set this flag on the head
    page; SLOB will not flag it at all.
 10 - BUDDY
-    a free memory block managed by the buddy system allocator
+    A free memory block managed by the buddy system allocator.
     The buddy system organizes free memory in blocks of various orders.
     An order N block has 2^N physically contiguous pages, with the BUDDY flag
     set for and _only_ for the first page.
···
 16 - COMPOUND_TAIL
     A compound page tail (see description above).
 17 - HUGE
-    this is an integral part of a HugeTLB page
+    This is an integral part of a HugeTLB page.
 19 - HWPOISON
-    hardware detected memory corruption on this page: don't touch the data!
+    Hardware detected memory corruption on this page: don't touch the data!
 20 - NOPAGE
-    no page frame exists at the requested address
+    No page frame exists at the requested address.
 21 - KSM
-    identical memory pages dynamically shared between one or more processes
+    Identical memory pages dynamically shared between one or more processes.
 22 - THP
-    contiguous pages which construct transparent hugepages
+    Contiguous pages which construct transparent hugepages.
 23 - OFFLINE
-    page is logically offline
+    The page is logically offline.
 24 - ZERO_PAGE
-    zero page for pfn_zero or huge_zero page
+    Zero page for pfn_zero or huge_zero page.
 25 - IDLE
-    page has not been accessed since it was marked idle (see
+    The page has not been accessed since it was marked idle (see
     :ref:`Documentation/admin-guide/mm/idle_page_tracking.rst <idle_page_tracking>`).
     Note that this flag may be stale in case the page was accessed via
     a PTE. To make sure the flag is up-to-date one has to read
     ``/sys/kernel/mm/page_idle/bitmap`` first.
 26 - PGTABLE
-    page is in use as a page table
+    The page is in use as a page table.
 
 IO related page flags
 ---------------------
 
 1 - ERROR
-   IO error occurred
+   IO error occurred.
 3 - UPTODATE
-   page has up-to-date data
+   The page has up-to-date data.
    ie. for file backed page: (in-memory data revision >= on-disk one)
 4 - DIRTY
-   page has been written to, hence contains new data
+   The page has been written to, hence contains new data.
    i.e. for file backed page: (in-memory data revision >  on-disk one)
 8 - WRITEBACK
-   page is being synced to disk
+   The page is being synced to disk.
 
 LRU related page flags
 ----------------------
 
 5 - LRU
-   page is in one of the LRU lists
+   The page is in one of the LRU lists.
 6 - ACTIVE
-   page is in the active LRU list
+   The page is in the active LRU list.
 18 - UNEVICTABLE
-   page is in the unevictable (non-)LRU list It is somehow pinned and
+   The page is in the unevictable (non-)LRU list It is somehow pinned and
    not a candidate for LRU page reclaims, e.g. ramfs pages,
-   shmctl(SHM_LOCK) and mlock() memory segments
+   shmctl(SHM_LOCK) and mlock() memory segments.
 2 - REFERENCED
-   page has been referenced since last LRU list enqueue/requeue
+   The page has been referenced since last LRU list enqueue/requeue.
 9 - RECLAIM
-   page will be reclaimed soon after its pageout IO completed
+   The page will be reclaimed soon after its pageout IO completed.
 11 - MMAP
-   a memory mapped page
+   A memory mapped page.
 12 - ANON
-   a memory mapped page that is not part of a file
+   A memory mapped page that is not part of a file.
 13 - SWAPCACHE
-   page is mapped to swap space, i.e. has an associated swap entry
+   The page is mapped to swap space, i.e. has an associated swap entry.
 14 - SWAPBACKED
-   page is backed by swap/RAM
+   The page is backed by swap/RAM.
 
 The page-types tool in the tools/vm directory can be used to query the
 above flags.