zircon/system/ulib/ftl/ftln/ftln_rd.c

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ftlnp.h"

// Type Definitions
typedef struct {
  ui32 ppn0;     // first physical page number if run_cnt != 0
  ui32 run_cnt;  // number of staged page reads
  ui8* buf;      // pointer to output buffer
} StagedRd;

// Local Function Definitions

// flush_pending_reads: Read all pages that are pending
//
//      Inputs: ftl = pointer to FTL control block
//              staged = pointer to structure holding 1st page number,
//                       page count, and output buffer pointer
//
//     Returns: 0 on success, -1 on error
//
static int flush_pending_reads(FTLN ftl, StagedRd* staged) {
  int status;
  ui32* b_ptr;

  // Issue pending reads.
  ftl->stats.read_page += staged->run_cnt;
  status = ndmReadPages(ftl->start_pn + staged->ppn0, staged->run_cnt, staged->buf, ftl->spare_buf,
                        ftl->ndm);

  // Adjust data buffer pointer.
  staged->buf += staged->run_cnt * ftl->page_size;

  // Get handle on blocks[] entry and increment block wear count.
  b_ptr = &ftl->bdata[staged->ppn0 / ftl->pgs_per_blk];
  INC_RC(ftl, b_ptr, staged->run_cnt);

  // Check if error was reported.
  if (status) {
    // If block needs to be recycled, set block read count to its max.
    if (status == 1) {
      SET_MAX_RC(ftl, b_ptr);
      status = 0;
    }

    // Else if fatal error, set errno and fatal I/O flag, return -1.
    else if (status == -2)
      return FtlnFatErr(ftl);
  }

  // Reset pending sequence and return status.
  staged->run_cnt = 0;
  return status;
}

// Global Function Definitions

// FtlnRdPages: Read count worth of virtual pages from FTL
//
//      Inputs: buf = pointer to where data is copied to
//              vpn = first volume page to read
//              count = number of consecutive pages to read
//              vol = pointer to FTL control block
//
//     Returns: 0 on success, -1 on error
//
int FtlnRdPages(void* buf, ui32 vpn, int count, void* vol) {
  FTLN ftl = vol;
  StagedRd staged;
  ui32 ppn;

  // Ensure request is within volume's range of provided pages.
  if (vpn + count > ftl->num_vpages) {
    ftl->logger.error(__FILE__, __LINE__, "FTL Read failed. Attempting to read page %u is out of range(max %u).",
                      vpn + count - 1, ftl->num_pages - 1);
    return FsError2(FTL_ASSERT, ENOSPC);
  }

  // If no pages to read, return success.
  if (count == 0)
    return 0;

  // If there's at least a block with a maximum read count, recycle.
  if (ftl->max_rc_blk != (ui32)-1)
    if (FtlnRecCheck(ftl, 0)) {
      ftl->logger.error(__FILE__, __LINE__, "FTL read recycle failed for page %u.");
      return -1;
    }

  // Set errno and return -1 if fatal I/O error occurred.
  if (ftl->flags & FTLN_FATAL_ERR)
    return FsError2(NDM_EIO, EIO);

  // Initialize structure for staging deferred consecutive page reads.
  staged.buf = buf;
  staged.run_cnt = 0;

  // Loop to read whole pages.
  do {
    // Check if reads are staged and PPN lookup could cause recycle.
    if (staged.run_cnt) {
      // If next PPN lookup could cause recycle, flush saved PPNs.
      if (FtlnRecNeeded(ftl, -1)) {
        if (flush_pending_reads(ftl, &staged))
          return -1;
      }

#if FS_ASSERT
      // Else confirm no physical page number changes due to recycle.
      else
        ftl->assert_no_recycle = TRUE;
#endif
    }

    // Prepare to potentially write one map page. Return -1 if error.
    if (FtlnRecCheck(ftl, -1)) {
      ftl->logger.error(__FILE__, __LINE__, "Failed to obtain free pages through block recycling.");
      return -1;
    }

    // Convert the virtual page number to its physical page number.
    if (FtlnMapGetPpn(ftl, vpn, &ppn) < 0) {
      ftl->logger.error(__FILE__, __LINE__, "Failed to obtain map physical page number.");
      return -1;
    }

#if FS_ASSERT
    // End check for no physical page number changes.
    ftl->assert_no_recycle = FALSE;
#endif

    // Check if page is unmapped.
    if (ppn == (ui32)-1) {
      // Flush pending reads if any.
      if (staged.run_cnt)
        if (flush_pending_reads(ftl, &staged))
          return -1;

      // Fill page with the value for unwritten data and
      // advance buffer pointer.
      memset(staged.buf, 0xFF, ftl->page_size);
      staged.buf += ftl->page_size;
    }

    // Else have valid mapped page number.
    else {
      // If next in sequence and in same block, add page to list.
      if ((staged.ppn0 + staged.run_cnt == ppn) &&
          (staged.ppn0 / ftl->pgs_per_blk == ppn / ftl->pgs_per_blk))
        ++staged.run_cnt;

      // Else flush pending reads, if any, and start new list.
      else {
        if (staged.run_cnt)
          if (flush_pending_reads(ftl, &staged))
            return -1;
        staged.ppn0 = ppn;
        staged.run_cnt = 1;
      }
    }

    // Adjust virtual page number and count.
    ++vpn;
  } while (--count > 0);

  // Flush pending reads if any.
  if (staged.run_cnt)
    if (flush_pending_reads(ftl, &staged))
      return -1;

  // Return success.
  return 0;
}

// FtlnRdPage: Read one physical page from flash
//
//      Inputs: ftl = pointer to FTL control block
//              ppn = physical page number of page to read from flash
//              rd_buf = buffer to hold read contents
//
//     Returns: 0 on success, -1 on error
//
int FtlnRdPage(FTLN ftl, ui32 ppn, void* rd_buf) {
  int status;
  ui32* b_ptr;

  // Set errno and return -1 if fatal I/O error occurred.
  if (ftl->flags & FTLN_FATAL_ERR)
    return FsError2(NDM_EIO, EIO);

  // Read page from flash. If error, set errno/fatal flag/return -1.
  ++ftl->stats.read_page;
  status = ndmReadPages(ftl->start_pn + ppn, 1, rd_buf, ftl->spare_buf, ftl->ndm);
  if (status < 0)
    return FtlnFatErr(ftl);

  // Get handle on block entry in blocks[].
  b_ptr = &ftl->bdata[ppn / ftl->pgs_per_blk];

  // If recycle requested, set read count to max. Else increment it.
  if (status)
    SET_MAX_RC(ftl, b_ptr);
  else
    INC_RC(ftl, b_ptr, 1);

  // Return success.
  return 0;
}