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Subject[PATCH v4] btrfs: add fs state details to error messages.
Date
When a filesystem goes read-only due to an error, multiple errors tend
to be reported, some of which are knock-on failures. Logging fs_states,
in btrfs_handle_fs_error() and btrfs_printk() helps distinguish the
first error from subsequent messages which may only exist due to an
error state.

Under the new format, most initial errors will look like:
`BTRFS: error (device loop0) in ...`
while subsequent errors will begin with:
`error (device loop0: state E) in ...`

An initial transaction abort error will look like
`error (device loop0: state A) in ...`
and subsequent messages will contain
`(device loop0: state EA) in ...`

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
---
v4:
- Adjusted state translation table to contain chars instead of
strings.

v3:
- Reworked btrfs_state_to_string to use an array mapping all states
to various error chars, or nothing, explicitly. Added error logging
for more states, as requested.
- Consolidated buffer length definition
- ttps://lore.kernel.org/linux-btrfs/8a2a73ab4b48a4e73d24cf7f10cc0fe245d50a84.1645562216.git.sweettea-kernel@dorminy.me/

v2:
- Changed btrfs_state_to_string() for clarity
- Removed superfluous whitespace change
- https://lore.kernel.org/linux-btrfs/084c136c6bb2d20ca0e91af7ded48306d52bb910.1645210326.git.sweettea-kernel@dorminy.me/

v1:
- https://lore.kernel.org/linux-btrfs/20220212191042.94954-1-sweettea-kernel@dorminy.me/

fs/btrfs/ctree.h | 2 ++
fs/btrfs/super.c | 62 +++++++++++++++++++++++++++++++++++++++++-------
2 files changed, 56 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 8992e0096163..3db337cd015a 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -148,6 +148,8 @@ enum {

/* Indicates there was an error cleaning up a log tree. */
BTRFS_FS_STATE_LOG_CLEANUP_ERROR,
+
+ BTRFS_FS_STATE_COUNT,
};

#define BTRFS_BACKREF_REV_MAX 256
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 4d947ba32da9..7ef6a3e494d0 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -66,6 +66,46 @@ static struct file_system_type btrfs_root_fs_type;

static int btrfs_remount(struct super_block *sb, int *flags, char *data);

+#define STATE_STRING_PREFACE ": state "
+#define STATE_STRING_BUF_LEN \
+ (sizeof(STATE_STRING_PREFACE) + BTRFS_FS_STATE_COUNT)
+
+/* Characters to print to indicate error conditions. RO is not an error. */
+static const char fs_state_chars[] = {
+ [BTRFS_FS_STATE_ERROR] = 'E',
+ [BTRFS_FS_STATE_REMOUNTING] = 'M',
+ [BTRFS_FS_STATE_RO] = 0,
+ [BTRFS_FS_STATE_TRANS_ABORTED] = 'A',
+ [BTRFS_FS_STATE_DEV_REPLACING] = 'P',
+ [BTRFS_FS_STATE_DUMMY_FS_INFO] = 0,
+ [BTRFS_FS_STATE_NO_CSUMS] = 0,
+ [BTRFS_FS_STATE_LOG_CLEANUP_ERROR] = 'L',
+};
+
+static void btrfs_state_to_string(const struct btrfs_fs_info *info, char *buf)
+{
+ unsigned int bit;
+ unsigned int states_printed = 0;
+ char *curr = buf;
+
+ memcpy(curr, STATE_STRING_PREFACE, sizeof(STATE_STRING_PREFACE));
+ curr += sizeof(STATE_STRING_PREFACE) - 1;
+
+ for_each_set_bit(bit, &info->fs_state, sizeof(info->fs_state)) {
+ WARN_ON_ONCE(bit >= BTRFS_FS_STATE_COUNT);
+ if ((bit < BTRFS_FS_STATE_COUNT) && fs_state_chars[bit]) {
+ *curr++ = fs_state_chars[bit];
+ states_printed++;
+ }
+ }
+
+ /* If no states were printed, reset the buffer */
+ if (!states_printed)
+ curr = buf;
+
+ *curr++ = '\0';
+}
+
/*
* Generally the error codes correspond to their respective errors, but there
* are a few special cases.
@@ -128,6 +168,7 @@ void __btrfs_handle_fs_error(struct btrfs_fs_info *fs_info, const char *function
{
struct super_block *sb = fs_info->sb;
#ifdef CONFIG_PRINTK
+ char statestr[STATE_STRING_BUF_LEN];
const char *errstr;
#endif

@@ -140,6 +181,7 @@ void __btrfs_handle_fs_error(struct btrfs_fs_info *fs_info, const char *function

#ifdef CONFIG_PRINTK
errstr = btrfs_decode_error(errno);
+ btrfs_state_to_string(fs_info, statestr);
if (fmt) {
struct va_format vaf;
va_list args;
@@ -148,12 +190,12 @@ void __btrfs_handle_fs_error(struct btrfs_fs_info *fs_info, const char *function
vaf.fmt = fmt;
vaf.va = &args;

- pr_crit("BTRFS: error (device %s) in %s:%d: errno=%d %s (%pV)\n",
- sb->s_id, function, line, errno, errstr, &vaf);
+ pr_crit("BTRFS: error (device %s%s) in %s:%d: errno=%d %s (%pV)\n",
+ sb->s_id, statestr, function, line, errno, errstr, &vaf);
va_end(args);
} else {
- pr_crit("BTRFS: error (device %s) in %s:%d: errno=%d %s\n",
- sb->s_id, function, line, errno, errstr);
+ pr_crit("BTRFS: error (device %s%s) in %s:%d: errno=%d %s\n",
+ sb->s_id, statestr, function, line, errno, errstr);
}
#endif

@@ -240,11 +282,15 @@ void __cold btrfs_printk(const struct btrfs_fs_info *fs_info, const char *fmt, .
vaf.va = &args;

if (__ratelimit(ratelimit)) {
- if (fs_info)
- printk("%sBTRFS %s (device %s): %pV\n", lvl, type,
- fs_info->sb->s_id, &vaf);
- else
+ if (fs_info) {
+ char statestr[STATE_STRING_BUF_LEN];
+
+ btrfs_state_to_string(fs_info, statestr);
+ printk("%sBTRFS %s (device %s%s): %pV\n", lvl, type,
+ fs_info->sb->s_id, statestr, &vaf);
+ } else {
printk("%sBTRFS %s: %pV\n", lvl, type, &vaf);
+ }
}

va_end(args);
--
2.35.1
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