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authorRich Felker <dalias@libc.org>2016-05-20 16:57:47 -0700
committerRich Felker <dalias@libc.org>2016-06-08 21:43:55 +0000
commit122126c5387b8dd403423e6c4d5af7583a1f05bf (patch)
treeff5f721e45a0c713384b2a4fb5323d50d9ae162f
parent2dcd0af568b0cf583645c8a317dd12e344b1c72a (diff)
downloadlinux-sh-122126c5387b8dd403423e6c4d5af7583a1f05bf.tar.gz
tmpfs/ramfs: fix VM_MAYSHARE mappings for NOMMU
The nommu do_mmap expects f_op->get_unmapped_area to either succeed or return -ENOSYS for VM_MAYSHARE (e.g. private read-only) mappings. Returning addr in the non-MAP_SHARED case was completely wrong, and only happened to work because addr was 0. However, it prevented VM_MAYSHARE mappings from sharing backing with the fs cache, and forced such mappings (including shareable program text) to be copied whenever the number of mappings transitioned from 0 to 1, impacting performance and memory usage. Subsequent mappings beyond the first still correctly shared memory with the first. Instead, treat VM_MAYSHARE identically to VM_SHARED at the file ops level; do_mmap already handles the semantic differences between them. Signed-off-by: Rich Felker <dalias@libc.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Greg Ungerer <gerg@uclinux.org> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/ramfs/file-nommu.c8
1 files changed, 2 insertions, 6 deletions
diff --git a/fs/ramfs/file-nommu.c b/fs/ramfs/file-nommu.c
index a586467f6ff6..be3ddd189cd4 100644
--- a/fs/ramfs/file-nommu.c
+++ b/fs/ramfs/file-nommu.c
@@ -211,14 +211,11 @@ static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
struct page **pages = NULL, **ptr, *page;
loff_t isize;
- if (!(flags & MAP_SHARED))
- return addr;
-
/* the mapping mustn't extend beyond the EOF */
lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
isize = i_size_read(inode);
- ret = -EINVAL;
+ ret = -ENOSYS;
maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (pgoff >= maxpages)
goto out;
@@ -227,7 +224,6 @@ static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
goto out;
/* gang-find the pages */
- ret = -ENOMEM;
pages = kcalloc(lpages, sizeof(struct page *), GFP_KERNEL);
if (!pages)
goto out_free;
@@ -263,7 +259,7 @@ out:
*/
static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
{
- if (!(vma->vm_flags & VM_SHARED))
+ if (!(vma->vm_flags & (VM_SHARED | VM_MAYSHARE)))
return -ENOSYS;
file_accessed(file);