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Date: Tue, 15 Nov 2011 18:23:44 +0800
From: Cong Wang <amwang@...hat.com>
To: Amerigo Wang <amwang@...hat.com>
CC: linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
Hugh Dickins <hughd@...gle.com>, linux-mm@...ck.org,
Lennart Poettering <lennart@...ttering.net>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: Re: [Patch] tmpfs: add fallocate support
CC: Lennart Poettering <lennart@...ttering.net>
Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
On 2011/11/15 16:42, Amerigo Wang wrote:
> This patch adds fallocate support to tmpfs. I tested this patch
> with the following test case,
>
> % sudo mount -t tmpfs -o size=100 tmpfs /mnt
> % touch /mnt/foobar
> % echo hi> /mnt/foobar
> % fallocate -o 3 -l 5000 /mnt/foobar
> fallocate: /mnt/foobar: fallocate failed: No space left on device
> % fallocate -o 3 -l 3000 /mnt/foobar
> % ls -l /mnt/foobar
> -rw-rw-r-- 1 wangcong wangcong 3003 Nov 15 16:10 /mnt/foobar
> % dd if=/dev/zero of=/mnt/foobar seek=3 bs=1 count=3000
> 3000+0 records in
> 3000+0 records out
> 3000 bytes (3.0 kB) copied, 0.0153224 s, 196 kB/s
> % hexdump -C /mnt/foobar
> 00000000 68 69 0a 00 00 00 00 00 00 00 00 00 00 00 00 00 |hi..............|
> 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
> *
> 00000bb0 00 00 00 00 00 00 00 00 00 00 00 |...........|
> 00000bbb
> % cat /mnt/foobar
> hi
>
> Signed-off-by: WANG Cong<amwang@...hat.com>
>
> ---
> diff --git a/mm/shmem.c b/mm/shmem.c
> index d672250..438b7b8 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -30,6 +30,7 @@
> #include<linux/mm.h>
> #include<linux/export.h>
> #include<linux/swap.h>
> +#include<linux/falloc.h>
>
> static struct vfsmount *shm_mnt;
>
> @@ -1431,6 +1432,102 @@ 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;
> + struct address_space *mapping = inode->i_mapping;
> + struct shmem_inode_info *info = SHMEM_I(inode);
> + struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
> + pgoff_t start = DIV_ROUND_UP(offset, PAGE_CACHE_SIZE);
> + pgoff_t end = DIV_ROUND_UP((offset + len), PAGE_CACHE_SIZE);
> + pgoff_t index = start;
> + gfp_t gfp = mapping_gfp_mask(mapping);
> + loff_t i_size = i_size_read(inode);
> + struct page *page = NULL;
> + int ret;
> +
> + if ((offset + len)<= i_size)
> + return 0;
> +
> + if (!(mode& FALLOC_FL_KEEP_SIZE)) {
> + ret = inode_newsize_ok(inode, (offset + len));
> + if (ret)
> + return ret;
> + }
> +
> + if (start == end) {
> + if (!(mode& FALLOC_FL_KEEP_SIZE))
> + i_size_write(inode, offset + len);
> + return 0;
> + }
> +
> + if (shmem_acct_block(info->flags))
> + return -ENOSPC;
> +
> + if (sbinfo->max_blocks) {
> + unsigned long blocks = (end - index) * BLOCKS_PER_PAGE;
> + if (blocks + percpu_counter_sum(&sbinfo->used_blocks)
> + >= sbinfo->max_blocks) {
> + ret = -ENOSPC;
> + goto unacct;
> + }
> + }
> +
> + while (index< end) {
> + if (sbinfo->max_blocks)
> + percpu_counter_add(&sbinfo->used_blocks, BLOCKS_PER_PAGE);
> +
> + page = shmem_alloc_page(gfp, info, index);
> + if (!page) {
> + ret = -ENOMEM;
> + goto decused;
> + }
> +
> + SetPageSwapBacked(page);
> + __set_page_locked(page);
> + ret = mem_cgroup_cache_charge(page, current->mm,
> + gfp& GFP_RECLAIM_MASK);
> + if (!ret)
> + ret = shmem_add_to_page_cache(page, mapping, index,
> + gfp, NULL);
> + if (ret)
> + goto unlock;
> + lru_cache_add_anon(page);
> +
> + spin_lock(&info->lock);
> + info->alloced++;
> + inode->i_blocks += BLOCKS_PER_PAGE;
> + inode->i_ctime = inode->i_mtime = CURRENT_TIME;
> + shmem_recalc_inode(inode);
> + spin_unlock(&info->lock);
> +
> + clear_highpage(page);
> + flush_dcache_page(page);
> + SetPageUptodate(page);
> + unlock_page(page);
> + page_cache_release(page);
> + cond_resched();
> + index++;
> + if (!(mode& FALLOC_FL_KEEP_SIZE))
> + i_size_write(inode, index<< PAGE_CACHE_SHIFT);
> + }
> +
> + goto unacct;
> +
> +unlock:
> + if (page) {
> + unlock_page(page);
> + page_cache_release(page);
> + }
> +decused:
> + if (sbinfo->max_blocks)
> + percpu_counter_sub(&sbinfo->used_blocks, BLOCKS_PER_PAGE);
> +unacct:
> + shmem_unacct_blocks(info->flags, 1);
> + return ret;
> +}
> +
> static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
> {
> struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
> @@ -2286,6 +2383,7 @@ 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
> };
>
--
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