On Fri, 18 Nov 2011, Cong Wang wrote: > It seems that systemd needs tmpfs to support fallocate, > see http://lkml.org/lkml/2011/10/20/275. This patch adds > fallocate support to tmpfs. > > As we already have shmem_truncate_range(), it is also easy > to add FALLOC_FL_PUNCH_HOLE support too. Thank you, this version looks much much nicer. I wouldn't call it bug-free (don't you need a page_cache_release after the unlock_page?), and I won't be reviewing it and testing it for a week or two - there's a lot about the semantics of fallocate and punch-hole that's not obvious, and I'll have to study the mail threads discussing them before checking your patch. First question that springs to mind (to which I shall easily find an answer): is it actually acceptable for fallocate() to return -ENOSPC when it has already completed a part of the work? But so long as the details don't end up complicating this significantly, since we anyway want to regularize the punch-hole situation by giving tmpfs the same interface to it as other filesystems, I now think it would be a bit perverse to disallow the original fallocate functionality that you implement here in-kernel. Thanks, Hugh > > Cc: Pekka Enberg <penberg@xxxxxxxxxx> > Cc: Hugh Dickins <hughd@xxxxxxxxxx> > Cc: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> > Cc: Lennart Poettering <lennart@xxxxxxxxxxxxxx> > Cc: Kay Sievers <kay.sievers@xxxxxxxx> > Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > Signed-off-by: WANG Cong <amwang@xxxxxxxxxx> > > --- > mm/shmem.c | 43 +++++++++++++++++++++++++++++++++++++++++++ > 1 files changed, 43 insertions(+), 0 deletions(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index d672250..96bf619 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 +1432,47 @@ 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 = i_size_read(inode); > + struct page *page = NULL; > + int ret = 0; > + > + mutex_lock(&inode->i_mutex); > + 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) > + goto unlock; > + if (page) > + unlock_page(page); > + index++; > + } > + if (!(mode & FALLOC_FL_KEEP_SIZE) && (index << PAGE_CACHE_SHIFT) > i_size) > + i_size_write(inode, index << PAGE_CACHE_SHIFT); > + > +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 +2328,7 @@ 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@xxxxxxxxx. 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: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>