From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 5F8676B00C0 for ; Wed, 23 Nov 2011 03:53:59 -0500 (EST) From: Cong Wang Subject: [V3 PATCH 1/2] tmpfs: add fallocate support Date: Wed, 23 Nov 2011 16:53:30 +0800 Message-Id: <1322038412-29013-1-git-send-email-amwang@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, Pekka Enberg , Christoph Hellwig , Hugh Dickins , Dave Hansen , Lennart Poettering , Kay Sievers , KOSAKI Motohiro , WANG Cong , linux-mm@kvack.org 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 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 Cc: Christoph Hellwig Cc: Hugh Dickins Cc: Dave Hansen Cc: Lennart Poettering Cc: Kay Sievers Cc: KOSAKI Motohiro Signed-off-by: WANG Cong --- mm/shmem.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 65 insertions(+), 0 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index d672250..65f7a27 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -30,6 +30,7 @@ #include #include #include +#include static struct vfsmount *shm_mnt; @@ -1431,6 +1432,69 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos, return error; } +static void shmem_truncate_page(struct inode *inode, pgoff_t index) +{ + loff_t start = index << PAGE_CACHE_SHIFT; + loff_t end = ((index + 1) << PAGE_CACHE_SHIFT) - 1; + shmem_truncate_range(inode, start, end); +} + +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; + + 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_truncate_page(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 +2350,7 @@ 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 }; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org