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From: | Daniel Henrique Barboza |
Subject: | Re: [Qemu-block] [PATCH v3 1/3] block: introducing 'bdrv_co_delete_file' interface |
Date: | Thu, 16 May 2019 08:42:50 -0300 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 |
Hi John, On 5/13/19 4:47 PM, John Snow wrote:
It looks like this one has gone un-noticed for a little while. On 3/26/19 5:17 PM, Daniel Henrique Barboza wrote:Adding to Block Drivers the capability of being able to clean up its created files can be useful in certain situations. For the LUKS driver, for instance, a failure in one of its authentication steps can leave files in the host that weren't there before. This patch adds the 'bdrv_co_delete_file' interface to block drivers and add it to the 'file' driver in file-posix.c. The implementation is given by 'raw_co_delete_file'. The helper 'bdrv_path_is_regular_file' is being used only in raw_co_delete_file at this moment, but it will be used inside LUKS in a later patch. Foreseeing this future use, let's put it in block.c and make it public. Suggested-by: Daniel P. Berrangé <address@hidden> Signed-off-by: Daniel Henrique Barboza <address@hidden> --- block.c | 11 +++++++++++ block/file-posix.c | 28 ++++++++++++++++++++++++++++ include/block/block.h | 1 + include/block/block_int.h | 6 ++++++ 4 files changed, 46 insertions(+) diff --git a/block.c b/block.c index 0a93ee9ac8..227362b282 100644 --- a/block.c +++ b/block.c @@ -621,6 +621,17 @@ int get_tmp_filename(char *filename, int size) #endif } +/** + * Helper that checks if a given string represents a regular + * local file. + */ +bool bdrv_path_is_regular_file(const char *path) +{ + struct stat st; + + return (stat(path, &st) == 0) && S_ISREG(st.st_mode); +} + /* * Detect host devices. By convention, /dev/cdrom[N] is always * recognized as a host CDROM. diff --git a/block/file-posix.c b/block/file-posix.c index d102f3b222..09d84bab37 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -2342,6 +2342,33 @@ static int coroutine_fn raw_co_create_opts(const char *filename, QemuOpts *opts, return raw_co_create(&options, errp); } +/** + * Co-routine function that erases a regular file. + */ +static int coroutine_fn raw_co_delete_file(const char *filename, + Error **errp)Do we need to mark functions that make no use of coroutines as coroutine_fn? I guess this way the interface is *allowed* to be a coroutine if other drivers need to make use of that. This function is used in a coroutine in patch 2. But to be honest, what I did here was to emulate the existing behavior of bdrv_create. Which is kind of lame if bdrv_create happens to have design problems or inconsistencies, but at least it's based on something that's already working. +{ + int ret; + + /* Skip file: protocol prefix */ + strstart(filename, "file:", &filename); +This sticks out as fragile to me, but I guess that's exactly how create works, so... OK. Yep, create does the same thing. Thanks, DHB + if (!bdrv_path_is_regular_file(filename)) { + ret = -ENOENT; + error_setg_errno(errp, -ret, "%s is not a regular file", filename); + goto done; + } + + ret = unlink(filename); + if (ret < 0) { + ret = -errno; + error_setg_errno(errp, -ret, "Error when deleting file %s", filename); + } + +done: + return ret; +} + /* * Find allocation range in @bs around offset @start. * May change underlying file descriptor's file offset. @@ -2867,6 +2894,7 @@ BlockDriver bdrv_file = { .bdrv_co_block_status = raw_co_block_status, .bdrv_co_invalidate_cache = raw_co_invalidate_cache, .bdrv_co_pwrite_zeroes = raw_co_pwrite_zeroes, + .bdrv_co_delete_file = raw_co_delete_file, .bdrv_co_preadv = raw_co_preadv, .bdrv_co_pwritev = raw_co_pwritev, diff --git a/include/block/block.h b/include/block/block.h index e452988b66..820643f96d 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -363,6 +363,7 @@ int bdrv_freeze_backing_chain(BlockDriverState *bs, BlockDriverState *base, Error **errp); void bdrv_unfreeze_backing_chain(BlockDriverState *bs, BlockDriverState *base); +bool bdrv_path_is_regular_file(const char *path); typedef struct BdrvCheckResult { int corruptions; diff --git a/include/block/block_int.h b/include/block/block_int.h index 01e855a066..74abb78ce7 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -309,6 +309,12 @@ struct BlockDriver { */ int coroutine_fn (*bdrv_co_flush)(BlockDriverState *bs); + /* + * Delete a local created file. + */ + int coroutine_fn (*bdrv_co_delete_file)(const char *filename, + Error **errp); + /* * Flushes all data that was already written to the OS all the way down to * the disk (for example file-posix.c calls fsync()).Seems alright at a glance, if we want this interface. Kevin, do we? --js |
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