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Commit 83e4fa9c authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

tmpfs: support fallocate FALLOC_FL_PUNCH_HOLE 



tmpfs has supported hole-punching since 2.6.16, via
madvise(,,MADV_REMOVE).

But nowadays fallocate(,FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE,,) is
the agreed way to punch holes.

So add shmem_fallocate() to support that, and tweak shmem_truncate_range()
to support partial pages at both the beginning and end of range (never
needed for madvise, which demands rounded addr and rounds up length).

Based-on-patch-by: default avatarCong Wang <amwang@redhat.com>
Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Cong Wang <amwang@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ec9516fb

mm/shmem.c

+57 −11
Original line number Diff line number Diff line
@@ -53,6 +53,7 @@ static struct vfsmount *shm_mnt; 
#include <linux/blkdev.h>

#include <linux/pagevec.h>

#include <linux/percpu_counter.h>

#include <linux/falloc.h>

#include <linux/splice.h>

#include <linux/security.h>

#include <linux/swapops.h>
@@ -432,21 +433,23 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend) 
	struct address_space *mapping = inode->i_mapping;

	struct shmem_inode_info *info = SHMEM_I(inode);

	pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;

	unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);

	pgoff_t end = (lend >> PAGE_CACHE_SHIFT);

	pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT;

	unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1);

	unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);

	struct pagevec pvec;

	pgoff_t indices[PAGEVEC_SIZE];

	long nr_swaps_freed = 0;

	pgoff_t index;

	int i;



	BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));

	if (lend == -1)

		end = -1;	/* unsigned, so actually very big */



	pagevec_init(&pvec, 0);

	index = start;

	while (index <= end) {

	while (index < end) {

		pvec.nr = shmem_find_get_pages_and_swap(mapping, index,

			min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,

				min(end - index, (pgoff_t)PAGEVEC_SIZE),

							pvec.pages, indices);

		if (!pvec.nr)

			break;
@@ -455,7 +458,7 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend) 
			struct page *page = pvec.pages[i];



			index = indices[i];

			if (index > end)

			if (index >= end)

				break;



			if (radix_tree_exceptional_entry(page)) {
@@ -479,22 +482,39 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend) 
		index++;

	}



	if (partial) {

	if (partial_start) {

		struct page *page = NULL;

		shmem_getpage(inode, start - 1, &page, SGP_READ, NULL);

		if (page) {

			zero_user_segment(page, partial, PAGE_CACHE_SIZE);

			unsigned int top = PAGE_CACHE_SIZE;

			if (start > end) {

				top = partial_end;

				partial_end = 0;

			}

			zero_user_segment(page, partial_start, top);

			set_page_dirty(page);

			unlock_page(page);

			page_cache_release(page);

		}

	}

	if (partial_end) {

		struct page *page = NULL;

		shmem_getpage(inode, end, &page, SGP_READ, NULL);

		if (page) {

			zero_user_segment(page, 0, partial_end);

			set_page_dirty(page);

			unlock_page(page);

			page_cache_release(page);

		}

	}

	if (start >= end)

		return;



	index = start;

	for ( ; ; ) {

		cond_resched();

		pvec.nr = shmem_find_get_pages_and_swap(mapping, index,

			min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,

				min(end - index, (pgoff_t)PAGEVEC_SIZE),

							pvec.pages, indices);

		if (!pvec.nr) {

			if (index == start)
@@ -502,7 +522,7 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend) 
			index = start;

			continue;

		}

		if (index == start && indices[0] > end) {

		if (index == start && indices[0] >= end) {

			shmem_deswap_pagevec(&pvec);

			pagevec_release(&pvec);

			break;
@@ -512,7 +532,7 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend) 
			struct page *page = pvec.pages[i];



			index = indices[i];

			if (index > end)

			if (index >= end)

				break;



			if (radix_tree_exceptional_entry(page)) {
@@ -1578,6 +1598,31 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos, 
	return error;

}



static long shmem_fallocate(struct file *file, int mode, loff_t offset,

							 loff_t len)

{

	struct inode *inode = file->f_path.dentry->d_inode;

	int error = -EOPNOTSUPP;



	mutex_lock(&inode->i_mutex);



	if (mode & FALLOC_FL_PUNCH_HOLE) {

		struct address_space *mapping = file->f_mapping;

		loff_t unmap_start = round_up(offset, PAGE_SIZE);

		loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;



		if ((u64)unmap_end > (u64)unmap_start)

			unmap_mapping_range(mapping, unmap_start,

					    1 + unmap_end - unmap_start, 0);

		shmem_truncate_range(inode, offset, offset + len - 1);

		/* No need to unmap again: hole-punching leaves COWed pages */

		error = 0;

	}



	mutex_unlock(&inode->i_mutex);

	return error;

}



static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)

{

	struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
@@ -2490,6 +2535,7 @@ static const struct file_operations shmem_file_operations = { 
	.fsync		= noop_fsync,

	.splice_read	= shmem_file_splice_read,

	.splice_write	= generic_file_splice_write,

	.fallocate	= shmem_fallocate,

#endif

};