blob: ecbc99ec7d367a3f9cb6d36b34332e156dbf7c05 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0-only
/* Network filesystem high-level buffered write support.
*
* Copyright (C) 2023 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/export.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/pagevec.h>
#include "internal.h"
/*
* Determined write method. Adjust netfs_folio_traces if this is changed.
*/
enum netfs_how_to_modify {
NETFS_FOLIO_IS_UPTODATE, /* Folio is uptodate already */
NETFS_JUST_PREFETCH, /* We have to read the folio anyway */
NETFS_WHOLE_FOLIO_MODIFY, /* We're going to overwrite the whole folio */
NETFS_MODIFY_AND_CLEAR, /* We can assume there is no data to be downloaded. */
NETFS_STREAMING_WRITE, /* Store incomplete data in non-uptodate page. */
NETFS_STREAMING_WRITE_CONT, /* Continue streaming write. */
NETFS_FLUSH_CONTENT, /* Flush incompatible content. */
};
static void netfs_set_group(struct folio *folio, struct netfs_group *netfs_group)
{
void *priv = folio_get_private(folio);
if (netfs_group && (!priv || priv == NETFS_FOLIO_COPY_TO_CACHE))
folio_attach_private(folio, netfs_get_group(netfs_group));
else if (!netfs_group && priv == NETFS_FOLIO_COPY_TO_CACHE)
folio_detach_private(folio);
}
/*
* Decide how we should modify a folio. We might be attempting to do
* write-streaming, in which case we don't want to a local RMW cycle if we can
* avoid it. If we're doing local caching or content crypto, we award that
* priority over avoiding RMW. If the file is open readably, then we also
* assume that we may want to read what we wrote.
*/
static enum netfs_how_to_modify netfs_how_to_modify(struct netfs_inode *ctx,
struct file *file,
struct folio *folio,
void *netfs_group,
size_t flen,
size_t offset,
size_t len,
bool maybe_trouble)
{
struct netfs_folio *finfo = netfs_folio_info(folio);
struct netfs_group *group = netfs_folio_group(folio);
loff_t pos = folio_file_pos(folio);
kenter("");
if (group != netfs_group && group != NETFS_FOLIO_COPY_TO_CACHE)
return NETFS_FLUSH_CONTENT;
if (folio_test_uptodate(folio))
return NETFS_FOLIO_IS_UPTODATE;
if (pos >= ctx->zero_point)
return NETFS_MODIFY_AND_CLEAR;
if (!maybe_trouble && offset == 0 && len >= flen)
return NETFS_WHOLE_FOLIO_MODIFY;
if (file->f_mode & FMODE_READ)
goto no_write_streaming;
if (netfs_is_cache_enabled(ctx)) {
/* We don't want to get a streaming write on a file that loses
* caching service temporarily because the backing store got
* culled.
*/
goto no_write_streaming;
}
if (!finfo)
return NETFS_STREAMING_WRITE;
/* We can continue a streaming write only if it continues on from the
* previous. If it overlaps, we must flush lest we suffer a partial
* copy and disjoint dirty regions.
*/
if (offset == finfo->dirty_offset + finfo->dirty_len)
return NETFS_STREAMING_WRITE_CONT;
return NETFS_FLUSH_CONTENT;
no_write_streaming:
if (finfo) {
netfs_stat(&netfs_n_wh_wstream_conflict);
return NETFS_FLUSH_CONTENT;
}
return NETFS_JUST_PREFETCH;
}
/*
* Grab a folio for writing and lock it. Attempt to allocate as large a folio
* as possible to hold as much of the remaining length as possible in one go.
*/
static struct folio *netfs_grab_folio_for_write(struct address_space *mapping,
loff_t pos, size_t part)
{
pgoff_t index = pos / PAGE_SIZE;
fgf_t fgp_flags = FGP_WRITEBEGIN;
if (mapping_large_folio_support(mapping))
fgp_flags |= fgf_set_order(pos % PAGE_SIZE + part);
return __filemap_get_folio(mapping, index, fgp_flags,
mapping_gfp_mask(mapping));
}
/*
* Update i_size and estimate the update to i_blocks to reflect the additional
* data written into the pagecache until we can find out from the server what
* the values actually are.
*/
static void netfs_update_i_size(struct netfs_inode *ctx, struct inode *inode,
loff_t i_size, loff_t pos, size_t copied)
{
blkcnt_t add;
size_t gap;
if (ctx->ops->update_i_size) {
ctx->ops->update_i_size(inode, pos);
return;
}
i_size_write(inode, pos);
#if IS_ENABLED(CONFIG_FSCACHE)
fscache_update_cookie(ctx->cache, NULL, &pos);
#endif
gap = SECTOR_SIZE - (i_size & (SECTOR_SIZE - 1));
if (copied > gap) {
add = DIV_ROUND_UP(copied - gap, SECTOR_SIZE);
inode->i_blocks = min_t(blkcnt_t,
DIV_ROUND_UP(pos, SECTOR_SIZE),
inode->i_blocks + add);
}
}
/**
* netfs_perform_write - Copy data into the pagecache.
* @iocb: The operation parameters
* @iter: The source buffer
* @netfs_group: Grouping for dirty pages (eg. ceph snaps).
*
* Copy data into pagecache pages attached to the inode specified by @iocb.
* The caller must hold appropriate inode locks.
*
* Dirty pages are tagged with a netfs_folio struct if they're not up to date
* to indicate the range modified. Dirty pages may also be tagged with a
* netfs-specific grouping such that data from an old group gets flushed before
* a new one is started.
*/
ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
struct netfs_group *netfs_group)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file_inode(file);
struct address_space *mapping = inode->i_mapping;
struct netfs_inode *ctx = netfs_inode(inode);
struct writeback_control wbc = {
.sync_mode = WB_SYNC_NONE,
.for_sync = true,
.nr_to_write = LONG_MAX,
.range_start = iocb->ki_pos,
.range_end = iocb->ki_pos + iter->count,
};
struct netfs_io_request *wreq = NULL;
struct netfs_folio *finfo;
struct folio *folio, *writethrough = NULL;
enum netfs_how_to_modify howto;
enum netfs_folio_trace trace;
unsigned int bdp_flags = (iocb->ki_flags & IOCB_NOWAIT) ? BDP_ASYNC : 0;
ssize_t written = 0, ret, ret2;
loff_t i_size, pos = iocb->ki_pos, from, to;
size_t max_chunk = PAGE_SIZE << MAX_PAGECACHE_ORDER;
bool maybe_trouble = false;
if (unlikely(test_bit(NETFS_ICTX_WRITETHROUGH, &ctx->flags) ||
iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC))
) {
wbc_attach_fdatawrite_inode(&wbc, mapping->host);
ret = filemap_write_and_wait_range(mapping, pos, pos + iter->count);
if (ret < 0) {
wbc_detach_inode(&wbc);
goto out;
}
wreq = netfs_begin_writethrough(iocb, iter->count);
if (IS_ERR(wreq)) {
wbc_detach_inode(&wbc);
ret = PTR_ERR(wreq);
wreq = NULL;
goto out;
}
if (!is_sync_kiocb(iocb))
wreq->iocb = iocb;
netfs_stat(&netfs_n_wh_writethrough);
} else {
netfs_stat(&netfs_n_wh_buffered_write);
}
do {
size_t flen;
size_t offset; /* Offset into pagecache folio */
size_t part; /* Bytes to write to folio */
size_t copied; /* Bytes copied from user */
ret = balance_dirty_pages_ratelimited_flags(mapping, bdp_flags);
if (unlikely(ret < 0))
break;
offset = pos & (max_chunk - 1);
part = min(max_chunk - offset, iov_iter_count(iter));
/* Bring in the user pages that we will copy from _first_ lest
* we hit a nasty deadlock on copying from the same page as
* we're writing to, without it being marked uptodate.
*
* 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.
*
* We rely on the page being held onto long enough by the LRU
* that we can grab it below if this causes it to be read.
*/
ret = -EFAULT;
if (unlikely(fault_in_iov_iter_readable(iter, part) == part))
break;
folio = netfs_grab_folio_for_write(mapping, pos, part);
if (IS_ERR(folio)) {
ret = PTR_ERR(folio);
break;
}
flen = folio_size(folio);
offset = pos & (flen - 1);
part = min_t(size_t, flen - offset, part);
/* Wait for writeback to complete. The writeback engine owns
* the info in folio->private and may change it until it
* removes the WB mark.
*/
if (folio_get_private(folio) &&
folio_wait_writeback_killable(folio)) {
ret = written ? -EINTR : -ERESTARTSYS;
goto error_folio_unlock;
}
if (signal_pending(current)) {
ret = written ? -EINTR : -ERESTARTSYS;
goto error_folio_unlock;
}
/* See if we need to prefetch the area we're going to modify.
* We need to do this before we get a lock on the folio in case
* there's more than one writer competing for the same cache
* block.
*/
howto = netfs_how_to_modify(ctx, file, folio, netfs_group,
flen, offset, part, maybe_trouble);
kdebug("howto %u", howto);
switch (howto) {
case NETFS_JUST_PREFETCH:
ret = netfs_prefetch_for_write(file, folio, offset, part);
if (ret < 0) {
kdebug("prefetch = %zd", ret);
goto error_folio_unlock;
}
break;
case NETFS_FOLIO_IS_UPTODATE:
case NETFS_WHOLE_FOLIO_MODIFY:
case NETFS_STREAMING_WRITE_CONT:
break;
case NETFS_MODIFY_AND_CLEAR:
zero_user_segment(&folio->page, 0, offset);
break;
case NETFS_STREAMING_WRITE:
ret = -EIO;
if (WARN_ON(folio_get_private(folio)))
goto error_folio_unlock;
break;
case NETFS_FLUSH_CONTENT:
trace_netfs_folio(folio, netfs_flush_content);
from = folio_pos(folio);
to = from + folio_size(folio) - 1;
folio_unlock(folio);
folio_put(folio);
ret = filemap_write_and_wait_range(mapping, from, to);
if (ret < 0)
goto error_folio_unlock;
continue;
}
if (mapping_writably_mapped(mapping))
flush_dcache_folio(folio);
copied = copy_folio_from_iter_atomic(folio, offset, part, iter);
flush_dcache_folio(folio);
/* Deal with a (partially) failed copy */
if (copied == 0) {
ret = -EFAULT;
goto error_folio_unlock;
}
trace = (enum netfs_folio_trace)howto;
switch (howto) {
case NETFS_FOLIO_IS_UPTODATE:
case NETFS_JUST_PREFETCH:
netfs_set_group(folio, netfs_group);
break;
case NETFS_MODIFY_AND_CLEAR:
zero_user_segment(&folio->page, offset + copied, flen);
netfs_set_group(folio, netfs_group);
folio_mark_uptodate(folio);
break;
case NETFS_WHOLE_FOLIO_MODIFY:
if (unlikely(copied < part)) {
maybe_trouble = true;
iov_iter_revert(iter, copied);
copied = 0;
folio_unlock(folio);
goto retry;
}
netfs_set_group(folio, netfs_group);
folio_mark_uptodate(folio);
break;
case NETFS_STREAMING_WRITE:
if (offset == 0 && copied == flen) {
netfs_set_group(folio, netfs_group);
folio_mark_uptodate(folio);
trace = netfs_streaming_filled_page;
break;
}
finfo = kzalloc(sizeof(*finfo), GFP_KERNEL);
if (!finfo) {
iov_iter_revert(iter, copied);
ret = -ENOMEM;
goto error_folio_unlock;
}
finfo->netfs_group = netfs_get_group(netfs_group);
finfo->dirty_offset = offset;
finfo->dirty_len = copied;
folio_attach_private(folio, (void *)((unsigned long)finfo |
NETFS_FOLIO_INFO));
break;
case NETFS_STREAMING_WRITE_CONT:
finfo = netfs_folio_info(folio);
finfo->dirty_len += copied;
if (finfo->dirty_offset == 0 && finfo->dirty_len == flen) {
if (finfo->netfs_group)
folio_change_private(folio, finfo->netfs_group);
else
folio_detach_private(folio);
folio_mark_uptodate(folio);
kfree(finfo);
trace = netfs_streaming_cont_filled_page;
}
break;
default:
WARN(true, "Unexpected modify type %u ix=%lx\n",
howto, folio->index);
ret = -EIO;
goto error_folio_unlock;
}
trace_netfs_folio(folio, trace);
/* Update the inode size if we moved the EOF marker */
pos += copied;
i_size = i_size_read(inode);
if (pos > i_size)
netfs_update_i_size(ctx, inode, i_size, pos, copied);
written += copied;
if (likely(!wreq)) {
folio_mark_dirty(folio);
folio_unlock(folio);
} else {
netfs_advance_writethrough(wreq, &wbc, folio, copied,
offset + copied == flen,
&writethrough);
/* Folio unlocked */
}
retry:
folio_put(folio);
folio = NULL;
cond_resched();
} while (iov_iter_count(iter));
out:
if (likely(written) && ctx->ops->post_modify)
ctx->ops->post_modify(inode);
if (unlikely(wreq)) {
ret2 = netfs_end_writethrough(wreq, &wbc, writethrough);
wbc_detach_inode(&wbc);
if (ret2 == -EIOCBQUEUED)
return ret2;
if (ret == 0)
ret = ret2;
}
iocb->ki_pos += written;
kleave(" = %zd [%zd]", written, ret);
return written ? written : ret;
error_folio_unlock:
folio_unlock(folio);
folio_put(folio);
goto out;
}
EXPORT_SYMBOL(netfs_perform_write);
/**
* netfs_buffered_write_iter_locked - write data to a file
* @iocb: IO state structure (file, offset, etc.)
* @from: iov_iter with data to write
* @netfs_group: Grouping for dirty pages (eg. ceph snaps).
*
* This function does all the work needed for actually writing data to a
* file. It does all basic checks, removes SUID from the file, updates
* modification times and calls proper subroutines depending on whether we
* do direct IO or a standard buffered write.
*
* The caller must hold appropriate locks around this function and have called
* generic_write_checks() already. The caller is also responsible for doing
* any necessary syncing afterwards.
*
* This function does *not* take care of syncing data in case of O_SYNC write.
* A caller has to handle it. This is mainly due to the fact that we want to
* avoid syncing under i_rwsem.
*
* Return:
* * number of bytes written, even for truncated writes
* * negative error code if no data has been written at all
*/
ssize_t netfs_buffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *from,
struct netfs_group *netfs_group)
{
struct file *file = iocb->ki_filp;
ssize_t ret;
trace_netfs_write_iter(iocb, from);
ret = file_remove_privs(file);
if (ret)
return ret;
ret = file_update_time(file);
if (ret)
return ret;
return netfs_perform_write(iocb, from, netfs_group);
}
EXPORT_SYMBOL(netfs_buffered_write_iter_locked);
/**
* netfs_file_write_iter - write data to a file
* @iocb: IO state structure
* @from: iov_iter with data to write
*
* Perform a write to a file, writing into the pagecache if possible and doing
* an unbuffered write instead if not.
*
* Return:
* * Negative error code if no data has been written at all of
* vfs_fsync_range() failed for a synchronous write
* * Number of bytes written, even for truncated writes
*/
ssize_t netfs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
struct netfs_inode *ictx = netfs_inode(inode);
ssize_t ret;
kenter("%llx,%zx,%llx", iocb->ki_pos, iov_iter_count(from), i_size_read(inode));
if (!iov_iter_count(from))
return 0;
if ((iocb->ki_flags & IOCB_DIRECT) ||
test_bit(NETFS_ICTX_UNBUFFERED, &ictx->flags))
return netfs_unbuffered_write_iter(iocb, from);
ret = netfs_start_io_write(inode);
if (ret < 0)
return ret;
ret = generic_write_checks(iocb, from);
if (ret > 0)
ret = netfs_buffered_write_iter_locked(iocb, from, NULL);
netfs_end_io_write(inode);
if (ret > 0)
ret = generic_write_sync(iocb, ret);
return ret;
}
EXPORT_SYMBOL(netfs_file_write_iter);
/*
* Notification that a previously read-only page is about to become writable.
* Note that the caller indicates a single page of a multipage folio.
*/
vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_group)
{
struct netfs_group *group;
struct folio *folio = page_folio(vmf->page);
struct file *file = vmf->vma->vm_file;
struct address_space *mapping = file->f_mapping;
struct inode *inode = file_inode(file);
struct netfs_inode *ictx = netfs_inode(inode);
vm_fault_t ret = VM_FAULT_RETRY;
int err;
kenter("%lx", folio->index);
sb_start_pagefault(inode->i_sb);
if (folio_lock_killable(folio) < 0)
goto out;
if (folio->mapping != mapping) {
folio_unlock(folio);
ret = VM_FAULT_NOPAGE;
goto out;
}
if (folio_wait_writeback_killable(folio)) {
ret = VM_FAULT_LOCKED;
goto out;
}
/* Can we see a streaming write here? */
if (WARN_ON(!folio_test_uptodate(folio))) {
ret = VM_FAULT_SIGBUS | VM_FAULT_LOCKED;
goto out;
}
group = netfs_folio_group(folio);
if (group != netfs_group && group != NETFS_FOLIO_COPY_TO_CACHE) {
folio_unlock(folio);
err = filemap_fdatawrite_range(mapping,
folio_pos(folio),
folio_pos(folio) + folio_size(folio));
switch (err) {
case 0:
ret = VM_FAULT_RETRY;
goto out;
case -ENOMEM:
ret = VM_FAULT_OOM;
goto out;
default:
ret = VM_FAULT_SIGBUS;
goto out;
}
}
if (folio_test_dirty(folio))
trace_netfs_folio(folio, netfs_folio_trace_mkwrite_plus);
else
trace_netfs_folio(folio, netfs_folio_trace_mkwrite);
netfs_set_group(folio, netfs_group);
file_update_time(file);
if (ictx->ops->post_modify)
ictx->ops->post_modify(inode);
ret = VM_FAULT_LOCKED;
out:
sb_end_pagefault(inode->i_sb);
return ret;
}
EXPORT_SYMBOL(netfs_page_mkwrite);