mm: write iovec cleanup
Hide some of the open-coded nr_segs tests into the iovec helpers. This is all to simplify generic_file_buffered_write, because that gets more complex in the next patch. Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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eb2be18931
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3 changed files with 77 additions and 96 deletions
28
mm/filemap.c
28
mm/filemap.c
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@ -1823,12 +1823,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
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/*
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* handle partial DIO write. Adjust cur_iov if needed.
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*/
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if (likely(nr_segs == 1))
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buf = iov->iov_base + written;
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else {
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filemap_set_next_iovec(&cur_iov, &iov_offset, written);
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buf = cur_iov->iov_base + iov_offset;
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}
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filemap_set_next_iovec(&cur_iov, nr_segs, &iov_offset, written);
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do {
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struct page *page;
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@ -1838,6 +1833,7 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
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size_t bytes; /* Bytes to write to page */
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size_t copied; /* Bytes copied from user */
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buf = cur_iov->iov_base + iov_offset;
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offset = (pos & (PAGE_CACHE_SIZE - 1));
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index = pos >> PAGE_CACHE_SHIFT;
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bytes = PAGE_CACHE_SIZE - offset;
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@ -1869,13 +1865,10 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
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if (unlikely(status))
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goto fs_write_aop_error;
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if (likely(nr_segs == 1))
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copied = filemap_copy_from_user(page, offset,
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buf, bytes);
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else
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copied = filemap_copy_from_user_iovec(page, offset,
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cur_iov, iov_offset, bytes);
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cur_iov, nr_segs, iov_offset, bytes);
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flush_dcache_page(page);
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status = a_ops->commit_write(file, page, offset, offset+bytes);
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if (unlikely(status < 0 || status == AOP_TRUNCATED_PAGE))
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goto fs_write_aop_error;
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@ -1886,20 +1879,11 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
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if (unlikely(status > 0)) /* filesystem did partial write */
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copied = status;
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if (likely(copied > 0)) {
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written += copied;
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count -= copied;
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pos += copied;
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buf += copied;
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if (unlikely(nr_segs > 1)) {
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filemap_set_next_iovec(&cur_iov,
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&iov_offset, copied);
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if (count)
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buf = cur_iov->iov_base + iov_offset;
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} else {
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iov_offset += copied;
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}
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}
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filemap_set_next_iovec(&cur_iov, nr_segs, &iov_offset, copied);
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unlock_page(page);
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mark_page_accessed(page);
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page_cache_release(page);
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98
mm/filemap.h
98
mm/filemap.h
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@ -22,68 +22,67 @@ __filemap_copy_from_user_iovec_inatomic(char *vaddr,
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/*
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* Copy as much as we can into the page and return the number of bytes which
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* were sucessfully copied. If a fault is encountered then clear the page
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* out to (offset+bytes) and return the number of bytes which were copied.
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*
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* NOTE: For this to work reliably we really want copy_from_user_inatomic_nocache
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* to *NOT* zero any tail of the buffer that it failed to copy. If it does,
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* and if the following non-atomic copy succeeds, then there is a small window
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* where the target page contains neither the data before the write, nor the
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* data after the write (it contains zero). A read at this time will see
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* data that is inconsistent with any ordering of the read and the write.
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* (This has been detected in practice).
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* were sucessfully copied. If a fault is encountered then return the number of
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* bytes which were copied.
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*/
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static inline size_t
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filemap_copy_from_user(struct page *page, unsigned long offset,
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const char __user *buf, unsigned bytes)
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{
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char *kaddr;
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int left;
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kaddr = kmap_atomic(page, KM_USER0);
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left = __copy_from_user_inatomic_nocache(kaddr + offset, buf, bytes);
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kunmap_atomic(kaddr, KM_USER0);
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if (left != 0) {
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/* Do it the slow way */
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kaddr = kmap(page);
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left = __copy_from_user_nocache(kaddr + offset, buf, bytes);
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kunmap(page);
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}
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return bytes - left;
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}
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/*
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* This has the same sideeffects and return value as filemap_copy_from_user().
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* The difference is that on a fault we need to memset the remainder of the
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* page (out to offset+bytes), to emulate filemap_copy_from_user()'s
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* single-segment behaviour.
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*/
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static inline size_t
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filemap_copy_from_user_iovec(struct page *page, unsigned long offset,
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const struct iovec *iov, size_t base, size_t bytes)
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filemap_copy_from_user_atomic(struct page *page, unsigned long offset,
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const struct iovec *iov, unsigned long nr_segs,
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size_t base, size_t bytes)
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{
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char *kaddr;
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size_t copied;
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kaddr = kmap_atomic(page, KM_USER0);
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copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,
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base, bytes);
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kunmap_atomic(kaddr, KM_USER0);
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if (copied != bytes) {
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kaddr = kmap(page);
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copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,
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base, bytes);
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if (bytes - copied)
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memset(kaddr + offset + copied, 0, bytes - copied);
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kunmap(page);
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if (likely(nr_segs == 1)) {
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int left;
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char __user *buf = iov->iov_base + base;
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left = __copy_from_user_inatomic_nocache(kaddr + offset,
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buf, bytes);
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copied = bytes - left;
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} else {
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copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset,
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iov, base, bytes);
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}
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kunmap_atomic(kaddr, KM_USER0);
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return copied;
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}
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/*
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* This has the same sideeffects and return value as
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* filemap_copy_from_user_atomic().
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* The difference is that it attempts to resolve faults.
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*/
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static inline size_t
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filemap_copy_from_user(struct page *page, unsigned long offset,
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const struct iovec *iov, unsigned long nr_segs,
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size_t base, size_t bytes)
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{
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char *kaddr;
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size_t copied;
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kaddr = kmap(page);
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if (likely(nr_segs == 1)) {
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int left;
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char __user *buf = iov->iov_base + base;
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left = __copy_from_user_nocache(kaddr + offset, buf, bytes);
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copied = bytes - left;
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} else {
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copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset,
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iov, base, bytes);
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}
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kunmap(page);
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return copied;
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}
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static inline void
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filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes)
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filemap_set_next_iovec(const struct iovec **iovp, unsigned long nr_segs,
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size_t *basep, size_t bytes)
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{
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if (likely(nr_segs == 1)) {
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*basep += bytes;
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} else {
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const struct iovec *iov = *iovp;
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size_t base = *basep;
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}
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*iovp = iov;
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*basep = base;
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}
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}
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#endif
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@ -15,7 +15,6 @@
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#include <linux/rmap.h>
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#include <linux/sched.h>
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#include <asm/tlbflush.h>
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#include "filemap.h"
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/*
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* We do use our own empty page to avoid interference with other users
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@ -288,6 +287,7 @@ __xip_file_write(struct file *filp, const char __user *buf,
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unsigned long index;
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unsigned long offset;
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size_t copied;
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char *kaddr;
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offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
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index = pos >> PAGE_CACHE_SHIFT;
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if (bytes > count)
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bytes = count;
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/*
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* Bring in the user page that we will copy from _first_.
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* Otherwise there's a nasty deadlock on copying from the
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* same page as we're writing to, without it being marked
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* up-to-date.
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*/
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fault_in_pages_readable(buf, bytes);
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page = a_ops->get_xip_page(mapping,
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index*(PAGE_SIZE/512), 0);
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if (IS_ERR(page) && (PTR_ERR(page) == -ENODATA)) {
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break;
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}
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copied = filemap_copy_from_user(page, offset, buf, bytes);
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fault_in_pages_readable(buf, bytes);
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kaddr = kmap_atomic(page, KM_USER0);
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copied = bytes -
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__copy_from_user_inatomic_nocache(kaddr, buf, bytes);
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kunmap_atomic(kaddr, KM_USER0);
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flush_dcache_page(page);
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if (likely(copied > 0)) {
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status = copied;
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