From: Paolo 'Blaisorblade' Giarrusso Date: Sat, 3 Sep 2005 22:54:55 +0000 (-0700) Subject: [PATCH] shmem_populate: avoid an useless check, and some comments X-Git-Tag: v2.6.14-rc1~963 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d44ed4f86892e350f4b16a3489b7e7c1a9bb7ead;p=linux-2.6 [PATCH] shmem_populate: avoid an useless check, and some comments Either shmem_getpage returns a failure, or it found a page, or it was told it couldn't do any I/O. So it's useless to check nonblock in the else branch. We could add a BUG() there but I preferred to comment the offending function. This was taken out from one Ingo Molnar's old patch I'm resurrecting. Signed-off-by: Paolo 'Blaisorblade' Giarrusso Cc: Ingo Molnar Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/filemap.c b/mm/filemap.c index edc54436fa..88611928e7 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1504,8 +1504,12 @@ repeat: return -EINVAL; page = filemap_getpage(file, pgoff, nonblock); + + /* XXX: This is wrong, a filesystem I/O error may have happened. Fix that as + * done in shmem_populate calling shmem_getpage */ if (!page && !nonblock) return -ENOMEM; + if (page) { err = install_page(mm, vma, addr, page, prot); if (err) { @@ -1513,6 +1517,9 @@ repeat: return err; } } else { + /* No page was found just because we can't read it in now (being + * here implies nonblock != 0), but the page may exist, so set + * the PTE to fault it in later. */ err = install_file_pte(mm, vma, addr, pgoff, prot); if (err) return err; diff --git a/mm/shmem.c b/mm/shmem.c index 5a81b1ee4f..08a3bc2fba 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1195,6 +1195,7 @@ static int shmem_populate(struct vm_area_struct *vma, err = shmem_getpage(inode, pgoff, &page, sgp, NULL); if (err) return err; + /* Page may still be null, but only if nonblock was set. */ if (page) { mark_page_accessed(page); err = install_page(mm, vma, addr, page, prot); @@ -1202,7 +1203,10 @@ static int shmem_populate(struct vm_area_struct *vma, page_cache_release(page); return err; } - } else if (nonblock) { + } else { + /* No page was found just because we can't read it in + * now (being here implies nonblock != 0), but the page + * may exist, so set the PTE to fault it in later. */ err = install_file_pte(mm, vma, addr, pgoff, prot); if (err) return err;