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[2001:8b0:bb71:7140:64::1]) by smtp.gmail.com with ESMTPSA id l11sm2448515wrt.23.2021.01.13.02.41.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 Jan 2021 02:41:29 -0800 (PST) Received: from localhost (disaster-area.hh.sledj.net [local]) by disaster-area.hh.sledj.net (OpenSMTPD) with ESMTPA id 348c33b9; Wed, 13 Jan 2021 10:41:29 +0000 (UTC) To: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org Subject: Re: [PATCH v4] block: report errno when flock fcntl fails In-Reply-To: References: <20210112152726.2217792-1-david.edmondson@oracle.com> X-HGTTG: zarquon From: David Edmondson X-Now-Playing: Nils Frahm - Spaces: For - Peter - Toilet Brushes - More Date: Wed, 13 Jan 2021 10:41:28 +0000 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Received-SPF: neutral client-ip=2a00:1450:4864:20::430; envelope-from=dme@dme.org; helo=mail-wr1-x430.google.com X-Spam_score_int: -10 X-Spam_score: -1.1 X-Spam_bar: - X-Spam_report: (-1.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_NEUTRAL=0.779, UNPARSEABLE_RELAY=0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wednesday, 2021-01-13 at 13:26:48 +03, Vladimir Sementsov-Ogievskiy wrote: > 12.01.2021 18:27, David Edmondson wrote: >> When a call to fcntl(2) for the purpose of manipulating file locks >> fails with an error other than EAGAIN or EACCES, report the error >> returned by fcntl. >> >> EAGAIN or EACCES are elided as they are considered to be common >> failures, indicating that a conflicting lock is held by another >> process. >> >> Signed-off-by: David Edmondson >> --- >> v3: >> - Remove the now unnecessary updates to the test framework (Max). >> - Elide the error detail for EAGAIN or EACCES when locking (Kevin, >> sort-of Max). >> - Philippe and Vladimir sent Reviewed-by, but things have changed >> noticeably, so I didn't add them (dme). >> >> v4: >> - Really, really remove the unnecessary updates to the test framework. >> >> block/file-posix.c | 52 +++++++++++++++++++++++++++++++++++++--------- >> 1 file changed, 42 insertions(+), 10 deletions(-) >> >> diff --git a/block/file-posix.c b/block/file-posix.c >> index 00cdaaa2d4..c5142f7ffa 100644 > > Hmm, not it looks like too much code duplication. Maybe, we can add a helper macro, like > > #define raw_lock_error_setg_errno(errp, os_error, fmt, ...) \ > do { > if (err == EAGAIN || err == EACCES) { > error_setg((errp), (fmt), ## __VA_ARGS__); > } else { > error_setg_errno((errp), (os_error), (fmt), ## __VA_ARGS__); > } > } while (0) > > We can't make a helper function instead, as error_setg_errno is already a macro and it wants to use __LINE__.. > > But I think that macro is better than duplication anyway. Okay. >> --- a/block/file-posix.c >> +++ b/block/file-posix.c >> @@ -836,7 +836,13 @@ static int raw_apply_lock_bytes(BDRVRawState *s, int fd, >> if ((perm_lock_bits & bit) && !(locked_perm & bit)) { >> ret = qemu_lock_fd(fd, off, 1, false); >> if (ret) { >> - error_setg(errp, "Failed to lock byte %d", off); >> + int err = -ret; >> + >> + if (err == EAGAIN || err == EACCES) { >> + error_setg(errp, "Failed to lock byte %d", off); >> + } else { >> + error_setg_errno(errp, err, "Failed to lock byte %d", off); >> + } >> return ret; >> } else if (s) { >> s->locked_perm |= bit; >> @@ -844,7 +850,13 @@ static int raw_apply_lock_bytes(BDRVRawState *s, int fd, >> } else if (unlock && (locked_perm & bit) && !(perm_lock_bits & bit)) { >> ret = qemu_unlock_fd(fd, off, 1); >> if (ret) { >> - error_setg(errp, "Failed to unlock byte %d", off); >> + int err = -ret; >> + >> + if (err == EAGAIN || err == EACCES) { >> + error_setg(errp, "Failed to lock byte %d", off); > > s/lock/unlock > >> + } else { >> + error_setg_errno(errp, err, "Failed to lock byte %d", off); > > and here. > > Which proves, that code duplication is a bad idea in general :) Ouch. Will fix. > >> + } >> return ret; >> } else if (s) { >> s->locked_perm &= ~bit; >> @@ -857,7 +869,13 @@ static int raw_apply_lock_bytes(BDRVRawState *s, int fd, >> if ((shared_perm_lock_bits & bit) && !(locked_shared_perm & bit)) { >> ret = qemu_lock_fd(fd, off, 1, false); >> if (ret) { >> - error_setg(errp, "Failed to lock byte %d", off); >> + int err = -ret; >> + >> + if (err == EAGAIN || err == EACCES) { >> + error_setg(errp, "Failed to lock byte %d", off); >> + } else { >> + error_setg_errno(errp, err, "Failed to lock byte %d", off); >> + } >> return ret; >> } else if (s) { >> s->locked_shared_perm |= bit; >> @@ -866,7 +884,7 @@ static int raw_apply_lock_bytes(BDRVRawState *s, int fd, >> !(shared_perm_lock_bits & bit)) { >> ret = qemu_unlock_fd(fd, off, 1); >> if (ret) { >> - error_setg(errp, "Failed to unlock byte %d", off); >> + error_setg_errno(errp, -ret, "Failed to unlock byte %d", off); > > Don't know, why same logic is not applied here.. Probably I've missed from the previous discussion. Anyway, if it is intentional exclusion, not bad to mention it in commit message. >From the documentation, it didn't seem to make sense that the unlock case would generate EAGAIN or EACCES for "someone is already holding the lock", so neither should be elided. I can add a note in the commit message. >> return ret; >> } else if (s) { >> s->locked_shared_perm &= ~bit; >> @@ -890,9 +908,16 @@ static int raw_check_lock_bytes(int fd, uint64_t perm, uint64_t shared_perm, >> ret = qemu_lock_fd_test(fd, off, 1, true); >> if (ret) { >> char *perm_name = bdrv_perm_names(p); >> - error_setg(errp, >> - "Failed to get \"%s\" lock", >> - perm_name); >> + int err = -ret; >> + >> + if (err == EAGAIN || err == EACCES) { >> + error_setg(errp, "Failed to get \"%s\" lock", >> + perm_name); > > fit in one line > >> + } else { >> + error_setg_errno(errp, err, >> + "Failed to get \"%s\" lock", >> + perm_name); > > fit in two lines.. > >> + } >> g_free(perm_name); >> return ret; >> } >> @@ -905,9 +930,16 @@ static int raw_check_lock_bytes(int fd, uint64_t perm, uint64_t shared_perm, >> ret = qemu_lock_fd_test(fd, off, 1, true); >> if (ret) { >> char *perm_name = bdrv_perm_names(p); >> - error_setg(errp, >> - "Failed to get shared \"%s\" lock", >> - perm_name); >> + int err = -ret; >> + >> + if (err == EAGAIN || err == EACCES) { >> + error_setg(errp, "Failed to get shared \"%s\" lock", >> + perm_name); >> + } else { >> + error_setg_errno(errp, err, >> + "Failed to get shared \"%s\" lock", >> + perm_name); >> + } >> g_free(perm_name); >> return ret; >> } >> > > also, I don't see much benefit in creating additional "err" variable instead of just use ret, but it's a kind of taste.. Okay. dme. -- Tonight I'm gonna bury that horse in the ground.