cregit-Linux how code gets into the kernel

Release 4.17 fs/iomap.c

Directory: fs
/*
 * Copyright (C) 2010 Red Hat, Inc.
 * Copyright (c) 2016 Christoph Hellwig.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 */
#include <linux/module.h>
#include <linux/compiler.h>
#include <linux/fs.h>
#include <linux/iomap.h>
#include <linux/uaccess.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/backing-dev.h>
#include <linux/buffer_head.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/dax.h>
#include <linux/sched/signal.h>

#include "internal.h"

/*
 * Execute a iomap write on a segment of the mapping that spans a
 * contiguous range of pages that have identical block mapping state.
 *
 * This avoids the need to map pages individually, do individual allocations
 * for each page and most importantly avoid the need for filesystem specific
 * locking per page. Instead, all the operations are amortised over the entire
 * range of pages. It is assumed that the filesystems will lock whatever
 * resources they require in the iomap_begin call, and release them in the
 * iomap_end call.
 */

loff_t iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags, const struct iomap_ops *ops, void *data, iomap_actor_t actor) { struct iomap iomap = { 0 }; loff_t written = 0, ret; /* * Need to map a range from start position for length bytes. This can * span multiple pages - it is only guaranteed to return a range of a * single type of pages (e.g. all into a hole, all mapped or all * unwritten). Failure at this point has nothing to undo. * * If allocation is required for this range, reserve the space now so * that the allocation is guaranteed to succeed later on. Once we copy * the data into the page cache pages, then we cannot fail otherwise we * expose transient stale data. If the reserve fails, we can safely * back out at this point as there is nothing to undo. */ ret = ops->iomap_begin(inode, pos, length, flags, &iomap); if (ret) return ret; if (WARN_ON(iomap.offset > pos)) return -EIO; if (WARN_ON(iomap.length == 0)) return -EIO; /* * Cut down the length to the one actually provided by the filesystem, * as it might not be able to give us the whole size that we requested. */ if (iomap.offset + iomap.length < pos + length) length = iomap.offset + iomap.length - pos; /* * Now that we have guaranteed that the space allocation will succeed. * we can do the copy-in page by page without having to worry about * failures exposing transient data. */ written = actor(inode, pos, length, data, &iomap); /* * Now the data has been copied, commit the range we've copied. This * should not fail unless the filesystem has had a fatal error. */ if (ops->iomap_end) { ret = ops->iomap_end(inode, pos, length, written > 0 ? written : 0, flags, &iomap); } return written ? written : ret; }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig17492.06%375.00%
Darrick J. Wong157.94%125.00%
Total189100.00%4100.00%


static void iomap_write_failed(struct inode *inode, loff_t pos, unsigned len) { loff_t i_size = i_size_read(inode); /* * Only truncate newly allocated pages beyoned EOF, even if the * write started inside the existing inode size. */ if (pos + len > i_size) truncate_pagecache_range(inode, max(pos, i_size), pos + len); }

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PersonTokensPropCommitsCommitProp
Christoph Hellwig50100.00%1100.00%
Total50100.00%1100.00%


static int iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags, struct page **pagep, struct iomap *iomap) { pgoff_t index = pos >> PAGE_SHIFT; struct page *page; int status = 0; BUG_ON(pos + len > iomap->offset + iomap->length); if (fatal_signal_pending(current)) return -EINTR; page = grab_cache_page_write_begin(inode->i_mapping, index, flags); if (!page) return -ENOMEM; status = __block_write_begin_int(page, pos, len, NULL, iomap); if (unlikely(status)) { unlock_page(page); put_page(page); page = NULL; iomap_write_failed(inode, pos, len); } *pagep = page; return status; }

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PersonTokensPropCommitsCommitProp
Christoph Hellwig14092.72%150.00%
Michal Hocko117.28%150.00%
Total151100.00%2100.00%


static int iomap_write_end(struct inode *inode, loff_t pos, unsigned len, unsigned copied, struct page *page) { int ret; ret = generic_write_end(NULL, inode->i_mapping, pos, len, copied, page, NULL); if (ret < len) iomap_write_failed(inode, pos, len); return ret; }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig67100.00%1100.00%
Total67100.00%1100.00%


static loff_t iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data, struct iomap *iomap) { struct iov_iter *i = data; long status = 0; ssize_t written = 0; unsigned int flags = AOP_FLAG_NOFS; do { struct page *page; unsigned long offset; /* Offset into pagecache page */ unsigned long bytes; /* Bytes to write to page */ size_t copied; /* Bytes copied from user */ offset = (pos & (PAGE_SIZE - 1)); bytes = min_t(unsigned long, PAGE_SIZE - offset, iov_iter_count(i)); again: if (bytes > length) bytes = length; /* * 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; } status = iomap_write_begin(inode, pos, bytes, flags, &page, iomap); if (unlikely(status)) break; if (mapping_writably_mapped(inode->i_mapping)) flush_dcache_page(page); copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); flush_dcache_page(page); status = iomap_write_end(inode, pos, bytes, copied, page); if (unlikely(status < 0)) break; copied = status; 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_SIZE - offset, iov_iter_single_seg_count(i)); goto again; } pos += copied; written += copied; length -= copied; balance_dirty_pages_ratelimited(inode->i_mapping); } while (iov_iter_count(i) && length); return written ? written : status; }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig286100.00%1100.00%
Total286100.00%1100.00%


ssize_t iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter, const struct iomap_ops *ops) { struct inode *inode = iocb->ki_filp->f_mapping->host; loff_t pos = iocb->ki_pos, ret = 0, written = 0; while (iov_iter_count(iter)) { ret = iomap_apply(inode, pos, iov_iter_count(iter), IOMAP_WRITE, ops, iter, iomap_write_actor); if (ret <= 0) break; pos += ret; written += ret; } return written ? written : ret; }

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Christoph Hellwig102100.00%2100.00%
Total102100.00%2100.00%

EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
static struct page * __iomap_read_page(struct inode *inode, loff_t offset) { struct address_space *mapping = inode->i_mapping; struct page *page; page = read_mapping_page(mapping, offset >> PAGE_SHIFT, NULL); if (IS_ERR(page)) return page; if (!PageUptodate(page)) { put_page(page); return ERR_PTR(-EIO); } return page; }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig78100.00%1100.00%
Total78100.00%1100.00%


static loff_t iomap_dirty_actor(struct inode *inode, loff_t pos, loff_t length, void *data, struct iomap *iomap) { long status = 0; ssize_t written = 0; do { struct page *page, *rpage; unsigned long offset; /* Offset into pagecache page */ unsigned long bytes; /* Bytes to write to page */ offset = (pos & (PAGE_SIZE - 1)); bytes = min_t(loff_t, PAGE_SIZE - offset, length); rpage = __iomap_read_page(inode, pos); if (IS_ERR(rpage)) return PTR_ERR(rpage); status = iomap_write_begin(inode, pos, bytes, AOP_FLAG_NOFS, &page, iomap); put_page(rpage); if (unlikely(status)) return status; WARN_ON_ONCE(!PageUptodate(page)); status = iomap_write_end(inode, pos, bytes, bytes, page); if (unlikely(status <= 0)) { if (WARN_ON_ONCE(status == 0)) return -EIO; return status; } cond_resched(); pos += status; written += status; length -= status; balance_dirty_pages_ratelimited(inode->i_mapping); } while (length); return written; }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig218100.00%2100.00%
Total218100.00%2100.00%


int iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len, const struct iomap_ops *ops) { loff_t ret; while (len) { ret = iomap_apply(inode, pos, len, IOMAP_WRITE, ops, NULL, iomap_dirty_actor); if (ret <= 0) return ret; pos += ret; len -= ret; } return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig70100.00%2100.00%
Total70100.00%2100.00%

EXPORT_SYMBOL_GPL(iomap_file_dirty);
static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset, unsigned bytes, struct iomap *iomap) { struct page *page; int status; status = iomap_write_begin(inode, pos, bytes, AOP_FLAG_NOFS, &page, iomap); if (status) return status; zero_user(page, offset, bytes); mark_page_accessed(page); return iomap_write_end(inode, pos, bytes, bytes, page); }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig86100.00%1100.00%
Total86100.00%1100.00%


static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes, struct iomap *iomap) { sector_t sector = (iomap->addr + (pos & PAGE_MASK) - iomap->offset) >> 9; return __dax_zero_page_range(iomap->bdev, iomap->dax_dev, sector, offset, bytes); }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig5288.14%133.33%
Dan J Williams46.78%133.33%
Andreas Gruenbacher35.08%133.33%
Total59100.00%3100.00%


static loff_t iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count, void *data, struct iomap *iomap) { bool *did_zero = data; loff_t written = 0; int status; /* already zeroed? we're done. */ if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN) return count; do { unsigned offset, bytes; offset = pos & (PAGE_SIZE - 1); /* Within page */ bytes = min_t(loff_t, PAGE_SIZE - offset, count); if (IS_DAX(inode)) status = iomap_dax_zero(pos, offset, bytes, iomap); else status = iomap_zero(inode, pos, offset, bytes, iomap); if (status < 0) return status; pos += bytes; count -= bytes; written += bytes; if (did_zero) *did_zero = true; } while (count > 0); return written; }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig166100.00%3100.00%
Total166100.00%3100.00%


int iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero, const struct iomap_ops *ops) { loff_t ret; while (len > 0) { ret = iomap_apply(inode, pos, len, IOMAP_ZERO, ops, did_zero, iomap_zero_range_actor); if (ret <= 0) return ret; pos += ret; len -= ret; } return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig76100.00%2100.00%
Total76100.00%2100.00%

EXPORT_SYMBOL_GPL(iomap_zero_range);
int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero, const struct iomap_ops *ops) { unsigned int blocksize = i_blocksize(inode); unsigned int off = pos & (blocksize - 1); /* Block boundary? Nothing to do */ if (!off) return 0; return iomap_zero_range(inode, pos, blocksize - off, did_zero, ops); }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig6492.75%266.67%
Fabian Frederick57.25%133.33%
Total69100.00%3100.00%

EXPORT_SYMBOL_GPL(iomap_truncate_page);
static loff_t iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length, void *data, struct iomap *iomap) { struct page *page = data; int ret; ret = __block_write_begin_int(page, pos, length, NULL, iomap); if (ret) return ret; block_commit_write(page, 0, length); return length; }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig70100.00%1100.00%
Total70100.00%1100.00%


int iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops) { struct page *page = vmf->page; struct inode *inode = file_inode(vmf->vma->vm_file); unsigned long length; loff_t offset, size; ssize_t ret; lock_page(page); size = i_size_read(inode); if ((page->mapping != inode->i_mapping) || (page_offset(page) > size)) { /* We overload EFAULT to mean page got truncated */ ret = -EFAULT; goto out_unlock; } /* page is wholly or partially inside EOF */ if (((page->index + 1) << PAGE_SHIFT) > size) length = size & ~PAGE_MASK; else length = PAGE_SIZE; offset = page_offset(page); while (length > 0) { ret = iomap_apply(inode, offset, length, IOMAP_WRITE | IOMAP_FAULT, ops, page, iomap_page_mkwrite_actor); if (unlikely(ret <= 0)) goto out_unlock; offset += ret; length -= ret; } set_page_dirty(page); wait_for_stable_page(page); return VM_FAULT_LOCKED; out_unlock: unlock_page(page); return block_page_mkwrite_return(ret); }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig20298.06%360.00%
Jan Kara20.97%120.00%
Dave Jiang20.97%120.00%
Total206100.00%5100.00%

EXPORT_SYMBOL_GPL(iomap_page_mkwrite); struct fiemap_ctx { struct fiemap_extent_info *fi; struct iomap prev; };
static int iomap_to_fiemap(struct fiemap_extent_info *fi, struct iomap *iomap, u32 flags) { switch (iomap->type) { case IOMAP_HOLE: /* skip holes */ return 0; case IOMAP_DELALLOC: flags |= FIEMAP_EXTENT_DELALLOC | FIEMAP_EXTENT_UNKNOWN; break; case IOMAP_UNWRITTEN: flags |= FIEMAP_EXTENT_UNWRITTEN; break; case IOMAP_MAPPED: break; } if (iomap->flags & IOMAP_F_MERGED) flags |= FIEMAP_EXTENT_MERGED; if (iomap->flags & IOMAP_F_SHARED) flags |= FIEMAP_EXTENT_SHARED; if (iomap->flags & IOMAP_F_DATA_INLINE) flags |= FIEMAP_EXTENT_DATA_INLINE; return fiemap_fill_next_extent(fi, iomap->offset, iomap->addr != IOMAP_NULL_ADDR ? iomap->addr : 0, iomap->length, flags); }

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PersonTokensPropCommitsCommitProp
Christoph Hellwig9377.50%240.00%
Andreas Gruenbacher1512.50%240.00%
Darrick J. Wong1210.00%120.00%
Total120100.00%5100.00%


static loff_t iomap_fiemap_actor(struct inode *inode, loff_t pos, loff_t length, void *data, struct iomap *iomap) { struct fiemap_ctx *ctx = data; loff_t ret = length; if (iomap->type == IOMAP_HOLE) return length; ret = iomap_to_fiemap(ctx->fi, &ctx->prev, 0); ctx->prev = *iomap; switch (ret) { case 0: /* success */ return length; case 1: /* extent array full */ return 0; default: return ret; } }

Contributors

PersonTokensPropCommitsCommitProp
Christoph Hellwig96100.00%1100.00%
Total96100.00%1100.00%


int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi, loff_t start, loff_t len, const struct iomap_ops *ops) { struct fiemap_ctx ctx; loff_t ret; memset(&ctx, 0, sizeof(ctx)); ctx.fi = fi; ctx.prev.type = IOMAP_HOLE; ret = fiemap_check_flags(fi, FIEMAP_FLAG_SYNC); if (ret) return ret; if (fi->fi_flags & FIEMAP_FLAG_SYNC) { ret = filemap_write_and_wait(inode->i_mapping); if (ret) return ret; } while (len > 0) { ret = iomap_apply(inode, start, len, IOMAP_REPORT, ops, &ctx, iomap_fiemap_actor); /* inode with no (attribute) mapping will give ENOENT */ if (ret == -ENOENT) break; if (ret < 0) return ret; if (ret == 0) break; start += ret; len -= ret; } if (ctx.prev.type != IOMAP_HOLE) { ret = iomap_to_fiemap(fi, &ctx.prev, FIEMAP_EXTENT_LAST); if (ret < 0) return ret; } return 0; }

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PersonTokensPropCommitsCommitProp
Christoph Hellwig18390.59%360.00%
Dave Chinner199.41%240.00%
Total202100.00%5100.00%

EXPORT_SYMBOL_GPL(iomap_fiemap);
static loff_t iomap_seek_hole_actor(struct inode *inode, loff_t offset, loff_t length, void *data, struct iomap *iomap) { switch (iomap->type) { case IOMAP_UNWRITTEN: offset = page_cache_seek_hole_data(inode, offset, length, SEEK_HOLE); if (offset < 0) return length; /* fall through */ case IOMAP_HOLE: *(loff_t *)data = offset; return 0; default: return length; } }

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PersonTokensPropCommitsCommitProp
Andreas Gruenbacher79100.00%1100.00%
Total79100.00%1100.00%


loff_t iomap_seek_hole(struct inode *inode, loff_t offset, const struct iomap_ops *ops) { loff_t size = i_size_read(inode); loff_t length = size - offset; loff_t ret; /* Nothing to be found before or beyond the end of the file. */ if (offset < 0 || offset >= size) return -ENXIO; while (length > 0) { ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops, &offset, iomap_seek_hole_actor); if (ret < 0) return ret; if (ret == 0) break; offset += ret; length -= ret; } return offset; }

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PersonTokensPropCommitsCommitProp
Andreas Gruenbacher10295.33%150.00%
Darrick J. Wong54.67%150.00%
Total107100.00%2100.00%

EXPORT_SYMBOL_GPL(iomap_seek_hole);
static loff_t iomap_seek_data_actor(struct inode *inode, loff_t offset, loff_t length, void *data, struct iomap *iomap) { switch (iomap->type) { case IOMAP_HOLE: return length; case IOMAP_UNWRITTEN: offset = page_cache_seek_hole_data(inode, offset, length, SEEK_DATA); if (offset < 0) return length; /*FALLTHRU*/ default: *(loff_t *)data = offset; return 0; } }

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PersonTokensPropCommitsCommitProp
Andreas Gruenbacher79100.00%1100.00%
Total79100.00%1100.00%


loff_t iomap_seek_data(struct inode *inode, loff_t offset, const struct iomap_ops *ops) { loff_t size = i_size_read(inode); loff_t length = size - offset; loff_t ret; /* Nothing to be found before or beyond the end of the file. */ if (offset < 0 || offset >= size) return -ENXIO; while (length > 0) { ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops, &offset, iomap_seek_data_actor); if (ret < 0) return ret; if (ret == 0) break; offset += ret; length -= ret; } if (length <= 0) return -ENXIO; return offset; }

Contributors

PersonTokensPropCommitsCommitProp
Andreas Gruenbacher11295.73%150.00%
Darrick J. Wong54.27%150.00%
Total117100.00%2100.00%

EXPORT_SYMBOL_GPL(iomap_seek_data); /* * Private flags for iomap_dio, must not overlap with the public ones in * iomap.h: */ #define IOMAP_DIO_WRITE (1 << 30) #define IOMAP_DIO_DIRTY (1 << 31) struct iomap_dio {