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Subject[PATCH v2] 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 some
fs_states, if any, 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 X) in ...`
and subsequent messages will contain
`(device loop0: state EX) in ...`

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
---
v2:
- Changed btrfs_state_to_string() for clarity
- Removed superfluous whitespace change

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

fs/btrfs/super.c | 53 ++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 45 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 4d947ba32da9..42429d68950d 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -66,6 +66,37 @@ 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 MAX_STATE_CHARS 2
+
+static void btrfs_state_to_string(const struct btrfs_fs_info *info, char *buf)
+{
+ unsigned int states_printed = 0;
+ char *curr = buf;
+
+ memcpy(curr, STATE_STRING_PREFACE, sizeof(STATE_STRING_PREFACE));
+ curr += sizeof(STATE_STRING_PREFACE) - 1;
+
+ /* If more states are reported, update MAX_STATE_CHARS also */
+ if (test_bit(BTRFS_FS_STATE_ERROR, &info->fs_state)) {
+ *curr++ = 'E';
+ states_printed++;
+ }
+
+ if (test_bit(BTRFS_FS_STATE_TRANS_ABORTED, &info->fs_state)) {
+ *curr++ = 'X';
+ states_printed++;
+ }
+
+ /* If no states were printed, reset the buffer */
+ if (!states_printed)
+ curr = buf;
+
+ WARN_ON_ONCE(states_printed > MAX_STATE_CHARS);
+
+ *curr++ = '\0';
+}
+
/*
* Generally the error codes correspond to their respective errors, but there
* are a few special cases.
@@ -128,6 +159,7 @@ 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[sizeof(STATE_STRING_PREFACE) + MAX_STATE_CHARS];
const char *errstr;
#endif

@@ -140,6 +172,7 @@ 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 +181,12 @@ 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 +273,15 @@ 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[sizeof(STATE_STRING_PREFACE) + MAX_STATE_CHARS];
+
+ 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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