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*参照元 [#w41e2dfa] #backlinks *説明 [#kbdd5d99] -パス: [[linux-2.6.33/]] -パス: [[linux-2.6.33/mm/filemap.c]] -FIXME: これは何？ --説明 **引数 [#o17668cd] -struct file *file -- --[[linux-2.6.33/file]] -struct iov_iter *i -- --[[linux-2.6.33/iov_iter]] -loff_t pos -- **返り値 [#oe377604] -ssize_t -- **参考 [#y8df98d1] *実装 [#j4d217bb] static ssize_t generic_perform_write(struct file *file, struct iov_iter *i, loff_t pos) { struct address_space *mapping = file->f_mapping; const struct address_space_operations *a_ops = mapping->a_ops; long status = 0; ssize_t written = 0; unsigned int flags = 0; - --[[linux-2.6.33/address_space]] - --[[linux-2.6.33/address_space_operations]] /* * Copies from kernel address space cannot fail (NFSD is a big user). */ if (segment_eq(get_fs(), KERNEL_DS)) flags |= AOP_FLAG_UNINTERRUPTIBLE; - --[[linux-2.6.33/KERNEL_DS]] - --[[linux-2.6.33/AOP_FLAG_UNINTERRUPTIBLE]] - --[[linux-2.6.33/segment_eq()]] - --[[linux-2.6.33/get_fs()]] do { struct page *page; pgoff_t index; /* Pagecache index for current page */ unsigned long offset; /* Offset into pagecache page */ unsigned long bytes; /* Bytes to write to page */ size_t copied; /* Bytes copied from user */ void *fsdata; - --[[linux-2.6.33/page]] - --[[linux-2.6.33/pgoff_t]] offset = (pos & (PAGE_CACHE_SIZE - 1)); index = pos >> PAGE_CACHE_SHIFT; bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, iov_iter_count(i)); - --[[linux-2.6.33/PAGE_CACHE_SIZE]] - --[[linux-2.6.33/PAGE_CACHE_SHIFT]] - --[[linux-2.6.33/min_t()]] - --[[linux-2.6.33/iov_iter_count()]] again: /* * Bring in the user page that we will copy from _first_. * Otherwise there's a nasty deadlock on copying from the * same page as we're writing to, without it being marked * up-to-date. * * Not only is this an optimisation, but it is also required * to check that the address is actually valid, when atomic * usercopies are used, below. */ if (unlikely(iov_iter_fault_in_readable(i, bytes))) { status = -EFAULT; break; } - --[[linux-2.6.33/unlikely()]] - --[[linux-2.6.33/iov_iter_fault_in_readable()]] status = a_ops->write_begin(file, mapping, pos, bytes, flags, &page, &fsdata); if (unlikely(status)) break; if (mapping_writably_mapped(mapping)) flush_dcache_page(page); - --[[linux-2.6.33/mapping_writably_mapped()]] - --[[linux-2.6.33/flush_dcache_page()]] pagefault_disable(); copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); pagefault_enable(); flush_dcache_page(page); - --[[linux-2.6.33/pagefault_disable()]] - --[[linux-2.6.33/iov_iter_copy_from_user_atomic()]] - --[[linux-2.6.33/pagefault_enable()]] mark_page_accessed(page); status = a_ops->write_end(file, mapping, pos, bytes, copied, page, fsdata); if (unlikely(status < 0)) break; copied = status; - --[[linux-2.6.33/mark_page_accessed()]] cond_resched(); - --[[linux-2.6.33/cond_resched()]] iov_iter_advance(i, copied); if (unlikely(copied == 0)) { /* * If we were unable to copy any data at all, we must * fall back to a single segment length write. * * If we didn't fallback here, we could livelock * because not all segments in the iov can be copied at * once without a pagefault. */ bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset, iov_iter_single_seg_count(i)); goto again; } pos += copied; written += copied; - --[[linux-2.6.33/iov_iter_advance()]] - --[[linux-2.6.33/iov_iter_single_seg_count()]] balance_dirty_pages_ratelimited(mapping); - --[[linux-2.6.33/balance_dirty_pages_ratelimited()]] } while (iov_iter_count(i)); - --[[linux-2.6.33/iov_iter_count()]] return written ? written : status; } *コメント [#k85bc781]
