Revision a742994aa2e271eb8cd8e043d276515ec858ed73 authored by Filipe Manana on 13 February 2015, 16:56:14 UTC, committed by Chris Mason on 14 February 2015, 16:22:49 UTC
If we are recording in the tree log that an inode has new names (new hard
links were added), we would drop items, belonging to the inode, that we
shouldn't:
1) When the flag BTRFS_INODE_COPY_EVERYTHING is set in the inode's runtime
flags, we ended up dropping all the extent and xattr items that were
previously logged. This was done only in memory, since logging a new
name doesn't imply syncing the log;
2) When the flag BTRFS_INODE_COPY_EVERYTHING is set in the inode's runtime
flags, we ended up dropping all the xattr items that were previously
logged. Like the case before, this was done only in memory because
logging a new name doesn't imply syncing the log.
This led to some surprises in scenarios such as the following:
1) write some extents to an inode;
2) fsync the inode;
3) truncate the inode or delete/modify some of its xattrs
4) add a new hard link for that inode
5) fsync some other file, to force the log tree to be durably persisted
6) power failure happens
The next time the fs is mounted, the fsync log replay code is executed,
and the resulting file doesn't have the content it had when the last fsync
against it was performed, instead if has a content matching what it had
when the last transaction commit happened.
So change the behaviour such that when a new name is logged, only the inode
item and reference items are processed.
This is easy to reproduce with the test I just made for xfstests, whose
main body is:
_scratch_mkfs >> $seqres.full 2>&1
_init_flakey
_mount_flakey
# Create our test file with some data.
$XFS_IO_PROG -f -c "pwrite -S 0xaa -b 8K 0 8K" \
$SCRATCH_MNT/foo | _filter_xfs_io
# Make sure the file is durably persisted.
sync
# Append some data to our file, to increase its size.
$XFS_IO_PROG -f -c "pwrite -S 0xcc -b 4K 8K 4K" \
$SCRATCH_MNT/foo | _filter_xfs_io
# Fsync the file, so from this point on if a crash/power failure happens, our
# new data is guaranteed to be there next time the fs is mounted.
$XFS_IO_PROG -c "fsync" $SCRATCH_MNT/foo
# Now shrink our file to 5000 bytes.
$XFS_IO_PROG -c "truncate 5000" $SCRATCH_MNT/foo
# Now do an expanding truncate to a size larger than what we had when we last
# fsync'ed our file. This is just to verify that after power failure and
# replaying the fsync log, our file matches what it was when we last fsync'ed
# it - 12Kb size, first 8Kb of data had a value of 0xaa and the last 4Kb of
# data had a value of 0xcc.
$XFS_IO_PROG -c "truncate 32K" $SCRATCH_MNT/foo
# Add one hard link to our file. This made btrfs drop all of our file's
# metadata from the fsync log, including the metadata relative to the
# extent we just wrote and fsync'ed. This change was made only to the fsync
# log in memory, so adding the hard link alone doesn't change the persisted
# fsync log. This happened because the previous truncates set the runtime
# flag BTRFS_INODE_NEEDS_FULL_SYNC in the btrfs inode structure.
ln $SCRATCH_MNT/foo $SCRATCH_MNT/foo_link
# Now make sure the in memory fsync log is durably persisted.
# Creating and fsync'ing another file will do it.
# After this our persisted fsync log will no longer have metadata for our file
# foo that points to the extent we wrote and fsync'ed before.
touch $SCRATCH_MNT/bar
$XFS_IO_PROG -c "fsync" $SCRATCH_MNT/bar
# As expected, before the crash/power failure, we should be able to see a file
# with a size of 32Kb, with its first 5000 bytes having the value 0xaa and all
# the remaining bytes with value 0x00.
echo "File content before:"
od -t x1 $SCRATCH_MNT/foo
# Simulate a crash/power loss.
_load_flakey_table $FLAKEY_DROP_WRITES
_unmount_flakey
_load_flakey_table $FLAKEY_ALLOW_WRITES
_mount_flakey
# After mounting the fs again, the fsync log was replayed.
# The expected result is to see a file with a size of 12Kb, with its first 8Kb
# of data having the value 0xaa and its last 4Kb of data having a value of 0xcc.
# The btrfs bug used to leave the file as it used te be as of the last
# transaction commit - that is, with a size of 8Kb with all bytes having a
# value of 0xaa.
echo "File content after:"
od -t x1 $SCRATCH_MNT/foo
The test case for xfstests follows soon.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
1 parent 1a4bcf4
recordmcount.c
/*
* recordmcount.c: construct a table of the locations of calls to 'mcount'
* so that ftrace can find them quickly.
* Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved.
* Licensed under the GNU General Public License, version 2 (GPLv2).
*
* Restructured to fit Linux format, as well as other updates:
* Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
*/
/*
* Strategy: alter the .o file in-place.
*
* Append a new STRTAB that has the new section names, followed by a new array
* ElfXX_Shdr[] that has the new section headers, followed by the section
* contents for __mcount_loc and its relocations. The old shstrtab strings,
* and the old ElfXX_Shdr[] array, remain as "garbage" (commonly, a couple
* kilobytes.) Subsequent processing by /bin/ld (or the kernel module loader)
* will ignore the garbage regions, because they are not designated by the
* new .e_shoff nor the new ElfXX_Shdr[]. [In order to remove the garbage,
* then use "ld -r" to create a new file that omits the garbage.]
*/
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <getopt.h>
#include <elf.h>
#include <fcntl.h>
#include <setjmp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#ifndef EM_METAG
/* Remove this when these make it to the standard system elf.h. */
#define EM_METAG 174
#define R_METAG_ADDR32 2
#define R_METAG_NONE 3
#endif
#ifndef EM_AARCH64
#define EM_AARCH64 183
#define R_AARCH64_ABS64 257
#endif
static int fd_map; /* File descriptor for file being modified. */
static int mmap_failed; /* Boolean flag. */
static void *ehdr_curr; /* current ElfXX_Ehdr * for resource cleanup */
static char gpfx; /* prefix for global symbol name (sometimes '_') */
static struct stat sb; /* Remember .st_size, etc. */
static jmp_buf jmpenv; /* setjmp/longjmp per-file error escape */
static const char *altmcount; /* alternate mcount symbol name */
static int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
/* setjmp() return values */
enum {
SJ_SETJMP = 0, /* hardwired first return */
SJ_FAIL,
SJ_SUCCEED
};
/* Per-file resource cleanup when multiple files. */
static void
cleanup(void)
{
if (!mmap_failed)
munmap(ehdr_curr, sb.st_size);
else
free(ehdr_curr);
close(fd_map);
}
static void __attribute__((noreturn))
fail_file(void)
{
cleanup();
longjmp(jmpenv, SJ_FAIL);
}
static void __attribute__((noreturn))
succeed_file(void)
{
cleanup();
longjmp(jmpenv, SJ_SUCCEED);
}
/* ulseek, uread, ...: Check return value for errors. */
static off_t
ulseek(int const fd, off_t const offset, int const whence)
{
off_t const w = lseek(fd, offset, whence);
if (w == (off_t)-1) {
perror("lseek");
fail_file();
}
return w;
}
static size_t
uread(int const fd, void *const buf, size_t const count)
{
size_t const n = read(fd, buf, count);
if (n != count) {
perror("read");
fail_file();
}
return n;
}
static size_t
uwrite(int const fd, void const *const buf, size_t const count)
{
size_t const n = write(fd, buf, count);
if (n != count) {
perror("write");
fail_file();
}
return n;
}
static void *
umalloc(size_t size)
{
void *const addr = malloc(size);
if (addr == 0) {
fprintf(stderr, "malloc failed: %zu bytes\n", size);
fail_file();
}
return addr;
}
static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
static unsigned char *ideal_nop;
static char rel_type_nop;
static int (*make_nop)(void *map, size_t const offset);
static int make_nop_x86(void *map, size_t const offset)
{
uint32_t *ptr;
unsigned char *op;
/* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */
ptr = map + offset;
if (*ptr != 0)
return -1;
op = map + offset - 1;
if (*op != 0xe8)
return -1;
/* convert to nop */
ulseek(fd_map, offset - 1, SEEK_SET);
uwrite(fd_map, ideal_nop, 5);
return 0;
}
/*
* Get the whole file as a programming convenience in order to avoid
* malloc+lseek+read+free of many pieces. If successful, then mmap
* avoids copying unused pieces; else just read the whole file.
* Open for both read and write; new info will be appended to the file.
* Use MAP_PRIVATE so that a few changes to the in-memory ElfXX_Ehdr
* do not propagate to the file until an explicit overwrite at the last.
* This preserves most aspects of consistency (all except .st_size)
* for simultaneous readers of the file while we are appending to it.
* However, multiple writers still are bad. We choose not to use
* locking because it is expensive and the use case of kernel build
* makes multiple writers unlikely.
*/
static void *mmap_file(char const *fname)
{
void *addr;
fd_map = open(fname, O_RDWR);
if (fd_map < 0 || fstat(fd_map, &sb) < 0) {
perror(fname);
fail_file();
}
if (!S_ISREG(sb.st_mode)) {
fprintf(stderr, "not a regular file: %s\n", fname);
fail_file();
}
addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_PRIVATE,
fd_map, 0);
mmap_failed = 0;
if (addr == MAP_FAILED) {
mmap_failed = 1;
addr = umalloc(sb.st_size);
uread(fd_map, addr, sb.st_size);
}
return addr;
}
/* w8rev, w8nat, ...: Handle endianness. */
static uint64_t w8rev(uint64_t const x)
{
return ((0xff & (x >> (0 * 8))) << (7 * 8))
| ((0xff & (x >> (1 * 8))) << (6 * 8))
| ((0xff & (x >> (2 * 8))) << (5 * 8))
| ((0xff & (x >> (3 * 8))) << (4 * 8))
| ((0xff & (x >> (4 * 8))) << (3 * 8))
| ((0xff & (x >> (5 * 8))) << (2 * 8))
| ((0xff & (x >> (6 * 8))) << (1 * 8))
| ((0xff & (x >> (7 * 8))) << (0 * 8));
}
static uint32_t w4rev(uint32_t const x)
{
return ((0xff & (x >> (0 * 8))) << (3 * 8))
| ((0xff & (x >> (1 * 8))) << (2 * 8))
| ((0xff & (x >> (2 * 8))) << (1 * 8))
| ((0xff & (x >> (3 * 8))) << (0 * 8));
}
static uint32_t w2rev(uint16_t const x)
{
return ((0xff & (x >> (0 * 8))) << (1 * 8))
| ((0xff & (x >> (1 * 8))) << (0 * 8));
}
static uint64_t w8nat(uint64_t const x)
{
return x;
}
static uint32_t w4nat(uint32_t const x)
{
return x;
}
static uint32_t w2nat(uint16_t const x)
{
return x;
}
static uint64_t (*w8)(uint64_t);
static uint32_t (*w)(uint32_t);
static uint32_t (*w2)(uint16_t);
/* Names of the sections that could contain calls to mcount. */
static int
is_mcounted_section_name(char const *const txtname)
{
return strcmp(".text", txtname) == 0 ||
strcmp(".ref.text", txtname) == 0 ||
strcmp(".sched.text", txtname) == 0 ||
strcmp(".spinlock.text", txtname) == 0 ||
strcmp(".irqentry.text", txtname) == 0 ||
strcmp(".kprobes.text", txtname) == 0 ||
strcmp(".text.unlikely", txtname) == 0;
}
/* 32 bit and 64 bit are very similar */
#include "recordmcount.h"
#define RECORD_MCOUNT_64
#include "recordmcount.h"
/* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
* http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
* We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
* to imply the order of the members; the spec does not say so.
* typedef unsigned char Elf64_Byte;
* fails on MIPS64 because their <elf.h> already has it!
*/
typedef uint8_t myElf64_Byte; /* Type for a 8-bit quantity. */
union mips_r_info {
Elf64_Xword r_info;
struct {
Elf64_Word r_sym; /* Symbol index. */
myElf64_Byte r_ssym; /* Special symbol. */
myElf64_Byte r_type3; /* Third relocation. */
myElf64_Byte r_type2; /* Second relocation. */
myElf64_Byte r_type; /* First relocation. */
} r_mips;
};
static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
{
return w(((union mips_r_info){ .r_info = rp->r_info }).r_mips.r_sym);
}
static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
{
rp->r_info = ((union mips_r_info){
.r_mips = { .r_sym = w(sym), .r_type = type }
}).r_info;
}
static void
do_file(char const *const fname)
{
Elf32_Ehdr *const ehdr = mmap_file(fname);
unsigned int reltype = 0;
ehdr_curr = ehdr;
w = w4nat;
w2 = w2nat;
w8 = w8nat;
switch (ehdr->e_ident[EI_DATA]) {
static unsigned int const endian = 1;
default:
fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
ehdr->e_ident[EI_DATA], fname);
fail_file();
break;
case ELFDATA2LSB:
if (*(unsigned char const *)&endian != 1) {
/* main() is big endian, file.o is little endian. */
w = w4rev;
w2 = w2rev;
w8 = w8rev;
}
break;
case ELFDATA2MSB:
if (*(unsigned char const *)&endian != 0) {
/* main() is little endian, file.o is big endian. */
w = w4rev;
w2 = w2rev;
w8 = w8rev;
}
break;
} /* end switch */
if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0
|| w2(ehdr->e_type) != ET_REL
|| ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
fprintf(stderr, "unrecognized ET_REL file %s\n", fname);
fail_file();
}
gpfx = 0;
switch (w2(ehdr->e_machine)) {
default:
fprintf(stderr, "unrecognized e_machine %d %s\n",
w2(ehdr->e_machine), fname);
fail_file();
break;
case EM_386:
reltype = R_386_32;
make_nop = make_nop_x86;
ideal_nop = ideal_nop5_x86_32;
mcount_adjust_32 = -1;
break;
case EM_ARM: reltype = R_ARM_ABS32;
altmcount = "__gnu_mcount_nc";
break;
case EM_AARCH64:
reltype = R_AARCH64_ABS64; gpfx = '_'; break;
case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break;
case EM_METAG: reltype = R_METAG_ADDR32;
altmcount = "_mcount_wrapper";
rel_type_nop = R_METAG_NONE;
/* We happen to have the same requirement as MIPS */
is_fake_mcount32 = MIPS32_is_fake_mcount;
break;
case EM_MIPS: /* reltype: e_class */ gpfx = '_'; break;
case EM_PPC: reltype = R_PPC_ADDR32; gpfx = '_'; break;
case EM_PPC64: reltype = R_PPC64_ADDR64; gpfx = '_'; break;
case EM_S390: /* reltype: e_class */ gpfx = '_'; break;
case EM_SH: reltype = R_SH_DIR32; break;
case EM_SPARCV9: reltype = R_SPARC_64; gpfx = '_'; break;
case EM_X86_64:
make_nop = make_nop_x86;
ideal_nop = ideal_nop5_x86_64;
reltype = R_X86_64_64;
mcount_adjust_64 = -1;
break;
} /* end switch */
switch (ehdr->e_ident[EI_CLASS]) {
default:
fprintf(stderr, "unrecognized ELF class %d %s\n",
ehdr->e_ident[EI_CLASS], fname);
fail_file();
break;
case ELFCLASS32:
if (w2(ehdr->e_ehsize) != sizeof(Elf32_Ehdr)
|| w2(ehdr->e_shentsize) != sizeof(Elf32_Shdr)) {
fprintf(stderr,
"unrecognized ET_REL file: %s\n", fname);
fail_file();
}
if (w2(ehdr->e_machine) == EM_MIPS) {
reltype = R_MIPS_32;
is_fake_mcount32 = MIPS32_is_fake_mcount;
}
do32(ehdr, fname, reltype);
break;
case ELFCLASS64: {
Elf64_Ehdr *const ghdr = (Elf64_Ehdr *)ehdr;
if (w2(ghdr->e_ehsize) != sizeof(Elf64_Ehdr)
|| w2(ghdr->e_shentsize) != sizeof(Elf64_Shdr)) {
fprintf(stderr,
"unrecognized ET_REL file: %s\n", fname);
fail_file();
}
if (w2(ghdr->e_machine) == EM_S390) {
reltype = R_390_64;
mcount_adjust_64 = -14;
}
if (w2(ghdr->e_machine) == EM_MIPS) {
reltype = R_MIPS_64;
Elf64_r_sym = MIPS64_r_sym;
Elf64_r_info = MIPS64_r_info;
is_fake_mcount64 = MIPS64_is_fake_mcount;
}
do64(ghdr, fname, reltype);
break;
}
} /* end switch */
cleanup();
}
int
main(int argc, char *argv[])
{
const char ftrace[] = "/ftrace.o";
int ftrace_size = sizeof(ftrace) - 1;
int n_error = 0; /* gcc-4.3.0 false positive complaint */
int c;
int i;
while ((c = getopt(argc, argv, "w")) >= 0) {
switch (c) {
case 'w':
warn_on_notrace_sect = 1;
break;
default:
fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
return 0;
}
}
if ((argc - optind) < 1) {
fprintf(stderr, "usage: recordmcount [-w] file.o...\n");
return 0;
}
/* Process each file in turn, allowing deep failure. */
for (i = optind; i < argc; i++) {
char *file = argv[i];
int const sjval = setjmp(jmpenv);
int len;
/*
* The file kernel/trace/ftrace.o references the mcount
* function but does not call it. Since ftrace.o should
* not be traced anyway, we just skip it.
*/
len = strlen(file);
if (len >= ftrace_size &&
strcmp(file + (len - ftrace_size), ftrace) == 0)
continue;
switch (sjval) {
default:
fprintf(stderr, "internal error: %s\n", file);
exit(1);
break;
case SJ_SETJMP: /* normal sequence */
/* Avoid problems if early cleanup() */
fd_map = -1;
ehdr_curr = NULL;
mmap_failed = 1;
do_file(file);
break;
case SJ_FAIL: /* error in do_file or below */
++n_error;
break;
case SJ_SUCCEED: /* premature success */
/* do nothing */
break;
} /* end switch */
}
return !!n_error;
}
Computing file changes ...
