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Commit 707c21c8 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
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[PATCH] msync(MS_SYNC): don't hold mmap_sem while syncing 



It seems bad to hold mmap_sem while performing synchronous disk I/O.  Alter
the msync(MS_SYNC) code so that the lock is released while we sync the file.

Cc: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 9c50823e

mm/msync.c

+26 −23
Original line number Diff line number Diff line
@@ -132,35 +132,14 @@ static int msync_interval(struct vm_area_struct *vma, unsigned long addr, 
			unsigned long end, int flags,

			unsigned long *nr_pages_dirtied)

{

	int ret = 0;

	struct file *file = vma->vm_file;



	if ((flags & MS_INVALIDATE) && (vma->vm_flags & VM_LOCKED))

		return -EBUSY;



	if (file && (vma->vm_flags & VM_SHARED)) {

	if (file && (vma->vm_flags & VM_SHARED))

		*nr_pages_dirtied = msync_page_range(vma, addr, end);



		if (flags & MS_SYNC) {

			struct address_space *mapping = file->f_mapping;

			int err;



			ret = filemap_fdatawrite(mapping);

			if (file->f_op && file->f_op->fsync) {

				/*

				 * We don't take i_mutex here because mmap_sem

				 * is already held.

				 */

				err = file->f_op->fsync(file,file->f_dentry,1);

				if (err && !ret)

					ret = err;

			}

			err = filemap_fdatawait(mapping);

			if (!ret)

				ret = err;

		}

	}

	return ret;

	return 0;

}



asmlinkage long sys_msync(unsigned long start, size_t len, int flags)
@@ -233,6 +212,30 @@ asmlinkage long sys_msync(unsigned long start, size_t len, int flags) 
			fput(file);

			down_read(&current->mm->mmap_sem);

			vma = find_vma(current->mm, start);

		} else if ((flags & MS_SYNC) && file &&

				(vma->vm_flags & VM_SHARED)) {

			struct address_space *mapping;

			int err;



			get_file(file);

			up_read(&current->mm->mmap_sem);

			mapping = file->f_mapping;

			error = filemap_fdatawrite(mapping);

			if (file->f_op && file->f_op->fsync) {

				mutex_lock(&mapping->host->i_mutex);

				err = file->f_op->fsync(file,file->f_dentry,1);

				mutex_unlock(&mapping->host->i_mutex);

				if (err && !error)

					error = err;

			}

			err = filemap_fdatawait(mapping);

			if (err && !error)

				error = err;

			fput(file);

			down_read(&current->mm->mmap_sem);

			if (error)

				goto out_unlock;

			vma = find_vma(current->mm, start);

		} else {

			vma = vma->vm_next;

		}