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Commitce5542d

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When performing a base backup, check for read errors.
The old code didn't differentiate between a read error and aconcurrent truncation. fread reports both of these by returning 0;you have to use feof() or ferror() to distinguish between them,which this code did not do.It might be a better idea to use read() rather than fread() here,so that we can display a less-generic error message, but I'm notsure that would qualify as a back-patchable bug fix, so just dothis much for now.Jeevan Chalke, reviewed by Jeevan Ladhe and by me.Discussion:http://postgr.es/m/CA+TgmobG4ywMzL5oQq2a8YKp8x2p3p1LOMMcGqpS7aekT9+ETA@mail.gmail.com
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‎src/backend/replication/basebackup.c

Lines changed: 31 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -90,6 +90,18 @@ static char *statrelpath = NULL;
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*/
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#defineTHROTTLING_FREQUENCY8
9292

93+
/*
94+
* Checks whether we encountered any error in fread(). fread() doesn't give
95+
* any clue what has happened, so we check with ferror(). Also, neither
96+
* fread() nor ferror() set errno, so we just throw a generic error.
97+
*/
98+
#defineCHECK_FREAD_ERROR(fp,filename) \
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do { \
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if (ferror(fp)) \
101+
ereport(ERROR, \
102+
(errmsg("could not read from file \"%s\"", filename))); \
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} while (0)
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/* The actual number of bytes, transfer of which may cause sleep. */
94106
staticuint64throttling_sample;
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@@ -550,6 +562,8 @@ perform_base_backup(basebackup_options *opt)
550562
break;
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}
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565+
CHECK_FREAD_ERROR(fp,pathbuf);
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553567
if (len!=wal_segment_size)
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{
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CheckXLogRemoved(segno,tli);
@@ -1490,6 +1504,20 @@ sendFile(const char *readfilename, const char *tarfilename, struct stat *statbuf
14901504

14911505
if (fread(buf+BLCKSZ*i,1,BLCKSZ,fp)!=BLCKSZ)
14921506
{
1507+
/*
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* If we hit end-of-file, a concurrent
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* truncation must have occurred, so break out
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* of this loop just as if the initial fread()
1511+
* returned 0. We'll drop through to the same
1512+
* code that handles that case. (We must fix
1513+
* up cnt first, though.)
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*/
1515+
if (feof(fp))
1516+
{
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cnt=BLCKSZ*i;
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break;
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}
1520+
14931521
ereport(ERROR,
14941522
(errcode_for_file_access(),
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errmsg("could not reread block %d of file \"%s\": %m",
@@ -1541,7 +1569,7 @@ sendFile(const char *readfilename, const char *tarfilename, struct stat *statbuf
15411569
len+=cnt;
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throttle(cnt);
15431571

1544-
if (len >=statbuf->st_size)
1572+
if (feof(fp)||len >=statbuf->st_size)
15451573
{
15461574
/*
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* Reached end of file. The file could be longer, if it was
@@ -1552,6 +1580,8 @@ sendFile(const char *readfilename, const char *tarfilename, struct stat *statbuf
15521580
}
15531581
}
15541582

1583+
CHECK_FREAD_ERROR(fp,readfilename);
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15551585
/* If the file was truncated while we were sending it, pad it with zeros */
15561586
if (len<statbuf->st_size)
15571587
{

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