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Message-Id: <1322544793-2676-1-git-send-email-amwang@redhat.com>
Date: Tue, 29 Nov 2011 13:33:12 +0800
From: Cong Wang <amwang@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: akpm@...ux-foundation.org, Pekka Enberg <penberg@...nel.org>,
Christoph Hellwig <hch@....de>,
Hugh Dickins <hughd@...gle.com>,
Dave Hansen <dave@...ux.vnet.ibm.com>,
Lennart Poettering <lennart@...ttering.net>,
Kay Sievers <kay.sievers@...y.org>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
WANG Cong <amwang@...hat.com>, linux-mm@...ck.org
Subject: [V4 PATCH 1/2] tmpfs: add fallocate support
Systemd needs tmpfs to support fallocate [1], to be able
to safely use mmap(), regarding SIGBUS, on files on the
/dev/shm filesystem. The glibc fallback loop for -ENOSYS
on fallocate is just ugly.
This patch adds fallocate support to tmpfs, and as we
already have shmem_truncate_range(), it is also easy to
add FALLOC_FL_PUNCH_HOLE support too.
1. http://lkml.org/lkml/2011/10/20/275
V3->V4:
Handle 'undo' ENOSPC more correctly.
V2->V3:
a) Read i_size directly after holding i_mutex;
b) Call page_cache_release() too after shmem_getpage();
c) Undo previous changes when -ENOSPC.
Cc: Pekka Enberg <penberg@...nel.org>
Cc: Christoph Hellwig <hch@....de>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Dave Hansen <dave@...ux.vnet.ibm.com>
Cc: Lennart Poettering <lennart@...ttering.net>
Cc: Kay Sievers <kay.sievers@...y.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Signed-off-by: WANG Cong <amwang@...hat.com>
---
mm/shmem.c | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 90 insertions(+), 0 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index d672250..90c835b 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;
@@ -1016,6 +1017,35 @@ failed:
return error;
}
+static void shmem_putpage_noswap(struct inode *inode, pgoff_t index)
+{
+ struct address_space *mapping = inode->i_mapping;
+ struct shmem_inode_info *info;
+ struct shmem_sb_info *sbinfo;
+ struct page *page;
+
+ page = find_lock_page(mapping, index);
+
+ if (page) {
+ info = SHMEM_I(inode);
+ sbinfo = SHMEM_SB(inode->i_sb);
+ shmem_acct_block(info->flags);
+ if (PageDirty(page)) {
+ ClearPageDirty(page);
+ delete_from_page_cache(page);
+ spin_lock(&info->lock);
+ info->alloced--;
+ inode->i_blocks -= BLOCKS_PER_PAGE;
+ spin_unlock(&info->lock);
+ }
+ if (sbinfo->max_blocks)
+ percpu_counter_add(&sbinfo->used_blocks, -1);
+ shmem_unacct_blocks(info->flags, 1);
+ unlock_page(page);
+ page_cache_release(page);
+ }
+}
+
static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
@@ -1431,6 +1461,65 @@ 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;
+ pgoff_t start = offset >> PAGE_CACHE_SHIFT;
+ pgoff_t end = DIV_ROUND_UP((offset + len), PAGE_CACHE_SIZE);
+ pgoff_t index = start;
+ loff_t i_size;
+ struct page *page = NULL;
+ int ret = 0;
+
+ if (IS_SWAPFILE(inode))
+ return -ETXTBSY;
+
+ mutex_lock(&inode->i_mutex);
+ i_size = inode->i_size;
+ if (mode & FALLOC_FL_PUNCH_HOLE) {
+ if (!(offset > i_size || (end << PAGE_CACHE_SHIFT) > i_size))
+ shmem_truncate_range(inode, offset,
+ (end << PAGE_CACHE_SHIFT) - 1);
+ goto unlock;
+ }
+
+ if (!(mode & FALLOC_FL_KEEP_SIZE)) {
+ ret = inode_newsize_ok(inode, (offset + len));
+ if (ret)
+ goto unlock;
+ }
+
+ while (index < end) {
+ ret = shmem_getpage(inode, index, &page, SGP_WRITE, NULL);
+ if (ret) {
+ if (ret == -ENOSPC)
+ goto undo;
+ else
+ goto unlock;
+ }
+ if (page) {
+ unlock_page(page);
+ page_cache_release(page);
+ }
+ index++;
+ }
+ if (!(mode & FALLOC_FL_KEEP_SIZE) && (index << PAGE_CACHE_SHIFT) > i_size)
+ i_size_write(inode, index << PAGE_CACHE_SHIFT);
+
+ goto unlock;
+
+undo:
+ while (index > start) {
+ shmem_putpage_noswap(inode, index);
+ index--;
+ }
+
+unlock:
+ mutex_unlock(&inode->i_mutex);
+ return ret;
+}
+
static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
{
struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
@@ -2286,6 +2375,7 @@ 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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