于 2011年11月16日 01:43, Dave Hansen 写道:
On Tue, 2011-11-15 at 18:23 +0800, Cong Wang wrote:+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;This seems to say that if the fallocate() call ends before the end of the file we should ignore the call. In other words, this can only be used to extend the file, but could not be used to fill in the holes of a sparse file. Is there a reason it was done that way?
Hmm, I missed the case of sparse file, so you are right, I need to fix it.
+ if (!(mode& FALLOC_FL_KEEP_SIZE)) { + ret = inode_newsize_ok(inode, (offset + len)); + if (ret) + return ret; + }inode_newsize_ok()'s comments say: * inode_newsize_ok must be called with i_mutex held. But I don't see any trace of it.
Hmm, even for tmpfs? I see none of the tmpfs code takes i_mutex lock though...
+ if (start == end) { + if (!(mode& FALLOC_FL_KEEP_SIZE)) + i_size_write(inode, offset + len); + return 0; + }There's a whitespace borkage like that 'mode&' all over this patch. Probably needs a little love.
Odd, it is fine in my local patch, and it passed checkpatch.pl check before I sent it. <...>
This seems to have borrowed quite generously from shmem_getpage_gfp(). Seems like some code consolidation is in order before this level of copy-n-paste.
Yes, I will separate the similar code. Thanks for review! -- 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>