From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Chun Yan Liu" Subject: Re: [PATCH V6 2/7] libxl_read_file_contents: add new entry to read sysfs file Date: Tue, 11 Aug 2015 20:37:09 -0600 Message-ID: <55CB21D50200006600057EB7@relay2.provo.novell.com> References: <1439202928-24813-1-git-send-email-cyliu@suse.com> <1439202928-24813-3-git-send-email-cyliu@suse.com> <20150811112655.GE7460@zion.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150811112655.GE7460@zion.uk.xensource.com> Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: wei.liu2@citrix.com Cc: Juergen Gross , ian.campbell@citrix.com, george.dunlap@eu.citrix.com, Ian.Jackson@eu.citrix.com, xen-devel@lists.xen.org, Jim Fehlig List-Id: xen-devel@lists.xenproject.org >>> On 8/11/2015 at 07:26 PM, in message <20150811112655.GE7460@zion.uk.xensource.com>, Wei Liu wrote: > On Mon, Aug 10, 2015 at 06:35:23PM +0800, Chunyan Liu wrote: > > Sysfs file has size=4096 but actual file content is less than that. > > Current libxl_read_file_contents will treat it as error when file size > > and actual file content differs, so reading sysfs file content with > > this function always fails. > > > > Add a new entry libxl_read_sysfs_file_contents to handle sysfs file > > specially. It would be used in later pvusb work. > > > > Signed-off-by: Chunyan Liu > > > > --- > > Changes: > > - read one more byte to check bigger size problem. > > > > tools/libxl/libxl_internal.h | 2 ++ > > tools/libxl/libxl_utils.c | 51 ++++++++++++++++++++++++++++++++++---------- > > 2 files changed, 42 insertions(+), 11 deletions(-) > > > > diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h > > index 6013628..f98f089 100644 > > --- a/tools/libxl/libxl_internal.h > > +++ b/tools/libxl/libxl_internal.h > > @@ -4001,6 +4001,8 @@ void libxl__bitmap_copy_best_effort(libxl__gc *gc, > libxl_bitmap *dptr, > > > > int libxl__count_physical_sockets(libxl__gc *gc, int *sockets); > > #endif > > +_hidden int libxl_read_sysfs_file_contents(libxl_ctx *ctx, const char > *filename, > > + void **data_r, int *datalen_r); > > Indentation looks wrong. > > > > > /* > > * Local variables: > > diff --git a/tools/libxl/libxl_utils.c b/tools/libxl/libxl_utils.c > > index bfc9699..9234efb 100644 > > --- a/tools/libxl/libxl_utils.c > > +++ b/tools/libxl/libxl_utils.c > > @@ -322,8 +322,10 @@ out: > > return rc; > > } > > > > -int libxl_read_file_contents(libxl_ctx *ctx, const char *filename, > > - void **data_r, int *datalen_r) { > > +static int libxl_read_file_contents_core(libxl_ctx *ctx, const char > *filename, > > + void **data_r, int *datalen_r, > > + bool tolerate_shrinking_file) > > +{ > > GC_INIT(ctx); > > FILE *f = 0; > > uint8_t *data = 0; > > @@ -359,20 +361,34 @@ int libxl_read_file_contents(libxl_ctx *ctx, const > char *filename, > > datalen = stab.st_size; > > > > if (stab.st_size && data_r) { > > - data = malloc(datalen); > > + data = malloc(datalen + 1); > > if (!data) goto xe; > > > > - rs = fread(data, 1, datalen, f); > > - if (rs != datalen) { > > - if (ferror(f)) > > + rs = fread(data, 1, datalen + 1, f); > > + if (rs > datalen) { > > + LOG(ERROR, "%s increased size while we were reading it", > > + filename); > > + goto xe; > > + } > > + > > + if (rs < datalen) { > > + if (ferror(f)) { > > LOGE(ERROR, "failed to read %s", filename); > > - else if (feof(f)) > > - LOG(ERROR, "%s changed size while we were reading it", > > - filename); > > - else > > + goto xe; > > + } else if (feof(f)) { > > + if (tolerate_shrinking_file) { > > + datalen = rs; > > + } else { > > + LOG(ERROR, "%s shrunk size while we were reading it", > > + filename); > > + goto xe; > > + } > > + } else { > > abort(); > > - goto xe; > > + } > > This is a bit bikeshedding, but you can leave "goto xe" out of two `if' > to reduce patch size. I guess you mean if (ferror(f)) and if (feof(f)) ? We can't leave 'goto xe' outside, since in if (feof(f)) && if (tolerate_shrinking_file), it's not error but an expected result in sysfs case. > > } > > + > > + data = realloc(data, datalen); > > Should check return value of realloc. Will add a check: if (!data) goto xe; Thanks, Chunyan > > The logic of this function reflects what has been discussed so far. > > Wei. > > > } > > > > if (fclose(f)) { > > @@ -396,6 +412,19 @@ int libxl_read_file_contents(libxl_ctx *ctx, const char > *filename, > > return e; > > } > > > > +int libxl_read_file_contents(libxl_ctx *ctx, const char *filename, > > + void **data_r, int *datalen_r) > > +{ > > + return libxl_read_file_contents_core(ctx, filename, data_r, datalen_r, > 0); > > +} > > + > > +int libxl_read_sysfs_file_contents(libxl_ctx *ctx, const char *filename, > > + void **data_r, int *datalen_r) > > +{ > > + return libxl_read_file_contents_core(ctx, filename, data_r, datalen_r, > 1); > > +} > > + > > + > > #define READ_WRITE_EXACTLY(rw, zero_is_eof, constdata) > \ > > > \ > > int libxl_##rw##_exactly(libxl_ctx *ctx, int fd, \ > > -- > > 2.1.4 > >