From: Matthew Wilcox Date: Wed, 4 Jun 2014 23:10:44 +0000 (-0700) Subject: mm/msync.c: sync only the requested range in msync() X-Git-Tag: v4.9.8~6270^2~16^2~94 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=7fc34a62ca4434a79c68e23e70ed26111b7a4cf8;p=platform%2Fkernel%2Flinux-rpi3.git mm/msync.c: sync only the requested range in msync() msync() currently syncs more than POSIX requires or BSD or Solaris implement. It is supposed to be equivalent to fdatasync(), not fsync(), and it is only supposed to sync the portion of the file that overlaps the range passed to msync. If the VMA is non-linear, fall back to syncing the entire file, but we still optimise to only fdatasync() the entire file, not the full fsync(). akpm: there are obvious concerns with bck-compatibility: is anyone relying on the undocumented side-effect for their data integrity? And how would they ever know if this change broke their data integrity? We think the risk is reasonably low, and this patch brings the kernel into line with other OS's and with what the manpage has always said... Signed-off-by: Matthew Wilcox Reviewed-by: Christoph Hellwig Acked-by: Jeff Moyer Cc: Chris Mason Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/msync.c b/mm/msync.c index 632df45..a5c6736 100644 --- a/mm/msync.c +++ b/mm/msync.c @@ -58,6 +58,7 @@ SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags) vma = find_vma(mm, start); for (;;) { struct file *file; + loff_t fstart, fend; /* Still start < end. */ error = -ENOMEM; @@ -77,12 +78,17 @@ SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags) goto out_unlock; } file = vma->vm_file; + fstart = start + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); + fend = fstart + (min(end, vma->vm_end) - start) - 1; start = vma->vm_end; if ((flags & MS_SYNC) && file && (vma->vm_flags & VM_SHARED)) { get_file(file); up_read(&mm->mmap_sem); - error = vfs_fsync(file, 0); + if (vma->vm_flags & VM_NONLINEAR) + error = vfs_fsync(file, 1); + else + error = vfs_fsync_range(file, fstart, fend, 1); fput(file); if (error || start >= end) goto out;